diff --git a/tests/wpt/metadata/FileAPI/url/url-in-tags-revoke.window.js.ini b/tests/wpt/metadata/FileAPI/url/url-in-tags-revoke.window.js.ini
index a9e46713244..76b398963ae 100644
--- a/tests/wpt/metadata/FileAPI/url/url-in-tags-revoke.window.js.ini
+++ b/tests/wpt/metadata/FileAPI/url/url-in-tags-revoke.window.js.ini
@@ -7,7 +7,7 @@
     expected: FAIL
 
   [Opening a blob URL in a new window immediately before revoking it works.]
-    expected: TIMEOUT
+    expected: FAIL
 
   [Opening a blob URL in a noopener about:blank window immediately before revoking it works.]
     expected: FAIL
diff --git a/tests/wpt/metadata/MANIFEST.json b/tests/wpt/metadata/MANIFEST.json
index 17de2d5ed8f..dcda26e69be 100644
--- a/tests/wpt/metadata/MANIFEST.json
+++ b/tests/wpt/metadata/MANIFEST.json
@@ -280382,6 +280382,15 @@
    "native-file-system/script-tests/FileSystemFileHandle-getFile.js": [
     []
    ],
+   "native-file-system/script-tests/FileSystemWritableFileStream-piped.js": [
+    []
+   ],
+   "native-file-system/script-tests/FileSystemWritableFileStream-write.js": [
+    []
+   ],
+   "native-file-system/script-tests/FileSystemWritableFileStream.js": [
+    []
+   ],
    "native-file-system/script-tests/FileSystemWriter.js": [
     []
    ],
@@ -374719,6 +374728,12 @@
      {}
     ]
    ],
+   "loading/lazyload/move-element-and-scroll.tentative.html": [
+    [
+     "loading/lazyload/move-element-and-scroll.tentative.html",
+     {}
+    ]
+   ],
    "loading/lazyload/not-rendered-below-viewport-image-loading-lazy.tentative.html": [
     [
      "loading/lazyload/not-rendered-below-viewport-image-loading-lazy.tentative.html",
@@ -374767,6 +374782,12 @@
      {}
     ]
    ],
+   "loading/lazyload/remove-element-and-scroll.tentative.html": [
+    [
+     "loading/lazyload/remove-element-and-scroll.tentative.html",
+     {}
+    ]
+   ],
    "loading/preloader-css-import-no-quote.tentative.html": [
     [
      "loading/preloader-css-import-no-quote.tentative.html",
@@ -379592,6 +379613,81 @@
      }
     ]
    ],
+   "native-file-system/native_FileSystemWritableFileStream-piped.tentative.https.manual.window.js": [
+    [
+     "native-file-system/native_FileSystemWritableFileStream-piped.tentative.https.manual.window.html",
+     {
+      "script_metadata": [
+       [
+        "script",
+        "/resources/testdriver.js"
+       ],
+       [
+        "script",
+        "resources/test-helpers.js"
+       ],
+       [
+        "script",
+        "resources/native-fs-test-helpers.js"
+       ],
+       [
+        "script",
+        "script-tests/FileSystemWritableFileStream-piped.js"
+       ]
+      ]
+     }
+    ]
+   ],
+   "native-file-system/native_FileSystemWritableFileStream-write.tentative.https.manual.window.js": [
+    [
+     "native-file-system/native_FileSystemWritableFileStream-write.tentative.https.manual.window.html",
+     {
+      "script_metadata": [
+       [
+        "script",
+        "/resources/testdriver.js"
+       ],
+       [
+        "script",
+        "resources/test-helpers.js"
+       ],
+       [
+        "script",
+        "resources/native-fs-test-helpers.js"
+       ],
+       [
+        "script",
+        "script-tests/FileSystemWritableFileStream-write.js"
+       ]
+      ]
+     }
+    ]
+   ],
+   "native-file-system/native_FileSystemWritableFileStream.tentative.https.manual.window.js": [
+    [
+     "native-file-system/native_FileSystemWritableFileStream.tentative.https.manual.window.html",
+     {
+      "script_metadata": [
+       [
+        "script",
+        "/resources/testdriver.js"
+       ],
+       [
+        "script",
+        "resources/test-helpers.js"
+       ],
+       [
+        "script",
+        "resources/native-fs-test-helpers.js"
+       ],
+       [
+        "script",
+        "script-tests/FileSystemWritableFileStream.js"
+       ]
+      ]
+     }
+    ]
+   ],
    "native-file-system/native_FileSystemWriter.tentative.https.manual.window.js": [
     [
      "native-file-system/native_FileSystemWriter.tentative.https.manual.window.html",
@@ -379971,6 +380067,134 @@
      }
     ]
    ],
+   "native-file-system/sandboxed_FileSystemWritableFileStream-piped.tentative.https.any.js": [
+    [
+     "native-file-system/sandboxed_FileSystemWritableFileStream-piped.tentative.https.any.html",
+     {
+      "script_metadata": [
+       [
+        "script",
+        "resources/test-helpers.js"
+       ],
+       [
+        "script",
+        "resources/sandboxed-fs-test-helpers.js"
+       ],
+       [
+        "script",
+        "../streams/resources/recording-streams.js"
+       ],
+       [
+        "script",
+        "script-tests/FileSystemWritableFileStream-piped.js"
+       ]
+      ]
+     }
+    ],
+    [
+     "native-file-system/sandboxed_FileSystemWritableFileStream-piped.tentative.https.any.worker.html",
+     {
+      "script_metadata": [
+       [
+        "script",
+        "resources/test-helpers.js"
+       ],
+       [
+        "script",
+        "resources/sandboxed-fs-test-helpers.js"
+       ],
+       [
+        "script",
+        "../streams/resources/recording-streams.js"
+       ],
+       [
+        "script",
+        "script-tests/FileSystemWritableFileStream-piped.js"
+       ]
+      ]
+     }
+    ]
+   ],
+   "native-file-system/sandboxed_FileSystemWritableFileStream-write.tentative.https.any.js": [
+    [
+     "native-file-system/sandboxed_FileSystemWritableFileStream-write.tentative.https.any.html",
+     {
+      "script_metadata": [
+       [
+        "script",
+        "resources/test-helpers.js"
+       ],
+       [
+        "script",
+        "resources/sandboxed-fs-test-helpers.js"
+       ],
+       [
+        "script",
+        "script-tests/FileSystemWritableFileStream-write.js"
+       ]
+      ]
+     }
+    ],
+    [
+     "native-file-system/sandboxed_FileSystemWritableFileStream-write.tentative.https.any.worker.html",
+     {
+      "script_metadata": [
+       [
+        "script",
+        "resources/test-helpers.js"
+       ],
+       [
+        "script",
+        "resources/sandboxed-fs-test-helpers.js"
+       ],
+       [
+        "script",
+        "script-tests/FileSystemWritableFileStream-write.js"
+       ]
+      ]
+     }
+    ]
+   ],
+   "native-file-system/sandboxed_FileSystemWritableFileStream.tentative.https.any.js": [
+    [
+     "native-file-system/sandboxed_FileSystemWritableFileStream.tentative.https.any.html",
+     {
+      "script_metadata": [
+       [
+        "script",
+        "resources/test-helpers.js"
+       ],
+       [
+        "script",
+        "resources/sandboxed-fs-test-helpers.js"
+       ],
+       [
+        "script",
+        "script-tests/FileSystemWritableFileStream.js"
+       ]
+      ]
+     }
+    ],
+    [
+     "native-file-system/sandboxed_FileSystemWritableFileStream.tentative.https.any.worker.html",
+     {
+      "script_metadata": [
+       [
+        "script",
+        "resources/test-helpers.js"
+       ],
+       [
+        "script",
+        "resources/sandboxed-fs-test-helpers.js"
+       ],
+       [
+        "script",
+        "script-tests/FileSystemWritableFileStream.js"
+       ]
+      ]
+     }
+    ]
+   ],
    "native-file-system/sandboxed_FileSystemWriter.tentative.https.any.js": [
     [
      "native-file-system/sandboxed_FileSystemWriter.tentative.https.any.html",
@@ -671141,6 +671365,10 @@
    "f7d887b18a228e648a5de45b890bfce371963cec",
    "testharness"
   ],
+  "loading/lazyload/move-element-and-scroll.tentative.html": [
+   "f9d89807b8c5575982e4d28f156cb604ae0bbd8b",
+   "testharness"
+  ],
   "loading/lazyload/not-rendered-below-viewport-image-loading-lazy.tentative.html": [
    "0c40d7dbcd832b379a3d8427f9390fca842439cd",
    "testharness"
@@ -671173,6 +671401,10 @@
    "58f8c3a4d5a1e21ce2afd9def3ab9b5870cc272f",
    "testharness"
   ],
+  "loading/lazyload/remove-element-and-scroll.tentative.html": [
+   "53708ceac75fa3421c4ecc1a8b91034c5a91c396",
+   "testharness"
+  ],
   "loading/lazyload/resources/image.png": [
    "b712825093805d1052b01047b1dbb102f0af8f0f",
    "support"
@@ -676393,6 +676625,18 @@
    "16c68c59b273663fb16847f121f38e03bb94cf19",
    "testharness"
   ],
+  "native-file-system/native_FileSystemWritableFileStream-piped.tentative.https.manual.window.js": [
+   "2c0299df12e9577261cce2f68d12a1bf744158c2",
+   "testharness"
+  ],
+  "native-file-system/native_FileSystemWritableFileStream-write.tentative.https.manual.window.js": [
+   "0efacf9e607d990bccf185b7d84d5f45220338d8",
+   "testharness"
+  ],
+  "native-file-system/native_FileSystemWritableFileStream.tentative.https.manual.window.js": [
+   "caf6fbd1c52a3cef603896f8ee98d9618e4dc92e",
+   "testharness"
+  ],
   "native-file-system/native_FileSystemWriter.tentative.https.manual.window.js": [
    "25d8ee995857fa67be2c41f048e882ec473f739d",
    "testharness"
@@ -676485,6 +676729,18 @@
    "fb93858fe7934b27244fa0ff828eac75c34b6629",
    "testharness"
   ],
+  "native-file-system/sandboxed_FileSystemWritableFileStream-piped.tentative.https.any.js": [
+   "eed6a561dc40e658b6b6c8d51766cdacc42a024c",
+   "testharness"
+  ],
+  "native-file-system/sandboxed_FileSystemWritableFileStream-write.tentative.https.any.js": [
+   "7ef0ea0ef82626eae74f152b94f898859aca6832",
+   "testharness"
+  ],
+  "native-file-system/sandboxed_FileSystemWritableFileStream.tentative.https.any.js": [
+   "16dbbe6a808a603c9b81482f733dcf09e84670ff",
+   "testharness"
+  ],
   "native-file-system/sandboxed_FileSystemWriter.tentative.https.any.js": [
    "8352e2487fe0823a2d353372757d833d85e98c4b",
    "testharness"
@@ -676525,6 +676781,18 @@
    "6b7d9f9a3171c96aaa2e1312451b3a9cac6c2e9b",
    "support"
   ],
+  "native-file-system/script-tests/FileSystemWritableFileStream-piped.js": [
+   "59fc1e3d1362b3ec90e3ef7a4f0981bdd4a21340",
+   "support"
+  ],
+  "native-file-system/script-tests/FileSystemWritableFileStream-write.js": [
+   "f14d79fd040a0e7fc7f19216fec1aec0ca23dec8",
+   "support"
+  ],
+  "native-file-system/script-tests/FileSystemWritableFileStream.js": [
+   "5acf93aec8cee8ef3a8389979e2a402acf5cbc7f",
+   "support"
+  ],
   "native-file-system/script-tests/FileSystemWriter.js": [
    "1c51d0b4eb771eec5a606263e72719be589aa317",
    "support"
@@ -710978,7 +711246,7 @@
    "support"
   ],
   "tools/requirements_mypy.txt": [
-   "50afed2bb2dec184caee69a1074e428d115c5b40",
+   "f3a56a6dd715ac6d6b01057a609a3e470ba8e303",
    "support"
   ],
   "tools/runner/css/bootstrap-theme.min.css": [
@@ -715338,7 +715606,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/browsers/base.py": [
-   "655344581973c15b657729feb736dd2073d79a30",
+   "fef052dd5ab495dad4342e086491723c761edcfd",
    "support"
   ],
   "tools/wptrunner/wptrunner/browsers/chrome.py": [
@@ -715366,7 +715634,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/browsers/epiphany.py": [
-   "8a0e5f578b2feb871ddd50ab08168c6b9d45e4b0",
+   "f6c4c602a38c043637cf9dbc8bbb5350ec94527e",
    "support"
   ],
   "tools/wptrunner/wptrunner/browsers/firefox.py": [
@@ -715410,11 +715678,11 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/browsers/webkit.py": [
-   "aa2862139450f682e6051c5f617ab8caf1960784",
+   "1be683ed26e43a9e10a1f82520811c33e90dad05",
    "support"
   ],
   "tools/wptrunner/wptrunner/browsers/webkitgtk_minibrowser.py": [
-   "d735f3c0792a6356c6270143205c55b7c02eef47",
+   "d8b9744bd743e39ce19f008e7f40cbc80e80107c",
    "support"
   ],
   "tools/wptrunner/wptrunner/config.py": [
@@ -715422,7 +715690,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/environment.py": [
-   "e79ae3750647f88bba44703181c208229800f658",
+   "7dcea4aeafabb9c481dccdc1aaf9bd153572bb7d",
    "support"
   ],
   "tools/wptrunner/wptrunner/executors/__init__.py": [
@@ -715466,7 +715734,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/executors/executorservo.py": [
-   "9cef1fb2d7f78e8729e51ff400b3df2402a2e94e",
+   "9eebfa59febf991bd41db25f2b02ea4c8c00195e",
    "support"
   ],
   "tools/wptrunner/wptrunner/executors/executorservodriver.py": [
@@ -715522,7 +715790,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/expectedtree.py": [
-   "4d505086bd8d991c953c34d38d8e1fa0cb920f99",
+   "7521f25b1344f5c50b8182a2b7a68278858f9b47",
    "support"
   ],
   "tools/wptrunner/wptrunner/font.py": [
@@ -715550,23 +715818,23 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/manifestexpected.py": [
-   "eae85b1f6661a67dff59ef78a9ed627e3e3603d8",
+   "65b53f0ab97b581b2b71277bd8f260f79a1afb12",
    "support"
   ],
   "tools/wptrunner/wptrunner/manifestinclude.py": [
-   "d302831a57abbaadd75fe49e094482dc14223ea3",
+   "b3ab2c0776571ffe4ca49e599e0a898c4a7c79a3",
    "support"
   ],
   "tools/wptrunner/wptrunner/manifestupdate.py": [
-   "2f2a8d543352d4c2128afd0314e8261668964d01",
+   "3cb1b5107924c4d897efccaf8f5de93df2311609",
    "support"
   ],
   "tools/wptrunner/wptrunner/metadata.py": [
-   "bf4d7a558abb7da117c95f896c1c8c3babd77219",
+   "aafc7d52250f62fdcd7025858f2273290c77d49e",
    "support"
   ],
   "tools/wptrunner/wptrunner/products.py": [
-   "e3117042709f99f4e0443dc0dfaf561ad0b548b0",
+   "abd84094bb33dbd13b3594a7acbe8467512a99ce",
    "support"
   ],
   "tools/wptrunner/wptrunner/stability.py": [
@@ -715598,7 +715866,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/testloader.py": [
-   "fa54ca361576318cb35ec716a1a159bdb532e6c8",
+   "f16cc14ceada70f781a2aaabb1c2f547cb9d61d1",
    "support"
   ],
   "tools/wptrunner/wptrunner/testrunner.py": [
@@ -715626,7 +715894,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/tests/test_expectedtree.py": [
-   "2308be9590e9004f41a492682d187a7b4fc57231",
+   "d71237a42dad58c69b686e6040b65f40064c9437",
    "support"
   ],
   "tools/wptrunner/wptrunner/tests/test_formatters.py": [
@@ -715634,7 +715902,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/tests/test_manifestexpected.py": [
-   "525915d1832ac8af1957a799615969e058eefca5",
+   "f3e4ce796a45c472a88fe022277e0347b4e98948",
    "support"
   ],
   "tools/wptrunner/wptrunner/tests/test_products.py": [
@@ -715646,15 +715914,15 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/tests/test_testloader.py": [
-   "e857cd43db6d281f95414230f52c984aad915118",
+   "836003d106038ab4303035eecca31774c9a26ce1",
    "support"
   ],
   "tools/wptrunner/wptrunner/tests/test_update.py": [
-   "5ed366788067c94245a8f7e1dadccb93da0493ab",
+   "a24e4a733dae576bf82f5b6e17a7bbe3f6d351ef",
    "support"
   ],
   "tools/wptrunner/wptrunner/tests/test_wpttest.py": [
-   "9bb3e1fd34e37c4430f752b87e4bb4e3bfa7f959",
+   "1a94a2f3303a7b5a1d5b2c553af6bbd1d8b45bc7",
    "support"
   ],
   "tools/wptrunner/wptrunner/update/__init__.py": [
@@ -715670,7 +715938,7 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/update/state.py": [
-   "64dbf1180604cd8df7a468e036447f95b80371b0",
+   "f8a83525cbd4706bdfbc99a518d2bac123d34e96",
    "support"
   ],
   "tools/wptrunner/wptrunner/update/sync.py": [
@@ -715694,11 +715962,11 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/wptcommandline.py": [
-   "923bdaa55857e793e8d6e8c587167360aed4ae94",
+   "91f1161b01b99f31ef1d3dde05333627bf4365b2",
    "support"
   ],
   "tools/wptrunner/wptrunner/wptlogging.py": [
-   "69cee744879eb6780cb99ec93123922e166d9e16",
+   "444d1d962d25873109977b937d96c86cb293cd8f",
    "support"
   ],
   "tools/wptrunner/wptrunner/wptmanifest/__init__.py": [
@@ -715758,11 +716026,11 @@
    "support"
   ],
   "tools/wptrunner/wptrunner/wptrunner.py": [
-   "cac172a5940ec696e3a3b279170f9712aaf4668d",
+   "7409dc26560af0be3a397bb73184137d8715811f",
    "support"
   ],
   "tools/wptrunner/wptrunner/wpttest.py": [
-   "67b57583424d08779114dc2fa030390e584d716f",
+   "4cbaedcdb0163776dfcf55d13afca4cdba05dc92",
    "support"
   ],
   "tools/wptserve/.gitignore": [
@@ -721278,7 +721546,7 @@
    "testharness"
   ],
   "wasm/jsapi/constructor/multi-value.any.js": [
-   "7fbac5b24f1a50568170e257552bdc7a7783ae25",
+   "2c53e3611e044c8ba44a5c0436d4409bc9f1af42",
    "testharness"
   ],
   "wasm/jsapi/constructor/validate.any.js": [
@@ -721326,7 +721594,7 @@
    "testharness"
   ],
   "wasm/jsapi/instanceTestFactory.js": [
-   "7ccf06c234a7ce5c17353f3bd74565b66c289952",
+   "c81672f208b1505430dd1ee909afaf12d9b2db20",
    "support"
   ],
   "wasm/jsapi/interface.any.js": [
@@ -721354,7 +721622,7 @@
    "testharness"
   ],
   "wasm/jsapi/module/customSections.any.js": [
-   "8e9732e5512d3295c445c110e949905cec0efbe6",
+   "09355979d84ade5385e7b3a5ac265eaa0da500cf",
    "testharness"
   ],
   "wasm/jsapi/module/exports.any.js": [
@@ -721394,7 +721662,7 @@
    "testharness"
   ],
   "wasm/jsapi/wasm-module-builder.js": [
-   "09ff891f52e2b4e9dd80fbc88586129cd0a910b6",
+   "82c6e04135f1b86df1a1d8e72c5f829c3297bb10",
    "support"
   ],
   "wasm/resources/load_wasm.js": [
diff --git a/tests/wpt/metadata/css/css-transitions/no-transition-from-ua-to-blocking-stylesheet.html.ini b/tests/wpt/metadata/css/css-transitions/no-transition-from-ua-to-blocking-stylesheet.html.ini
index 70a00a101f6..e35a452a186 100644
--- a/tests/wpt/metadata/css/css-transitions/no-transition-from-ua-to-blocking-stylesheet.html.ini
+++ b/tests/wpt/metadata/css/css-transitions/no-transition-from-ua-to-blocking-stylesheet.html.ini
@@ -1,2 +1,2 @@
 [no-transition-from-ua-to-blocking-stylesheet.html]
-  expected: FAIL
+  expected: TIMEOUT
diff --git a/tests/wpt/metadata/fetch/content-type/response.window.js.ini b/tests/wpt/metadata/fetch/content-type/response.window.js.ini
index a5ea66f4172..f37c04a5b81 100644
--- a/tests/wpt/metadata/fetch/content-type/response.window.js.ini
+++ b/tests/wpt/metadata/fetch/content-type/response.window.js.ini
@@ -309,24 +309,21 @@
   [<iframe>: separate response Content-Type: */* text/html]
     expected: FAIL
 
-  [<iframe>: combined response Content-Type: text/html;charset=gbk text/plain text/html]
-    expected: FAIL
-
   [<iframe>: combined response Content-Type: text/html;" \\" text/plain]
     expected: FAIL
 
-  [<iframe>: combined response Content-Type: text/html;" text/plain]
-    expected: FAIL
-
-  [<iframe>: separate response Content-Type: text/plain */*]
-    expected: FAIL
-
   [<iframe>: combined response Content-Type: text/html */*]
     expected: FAIL
 
-  [<iframe>: combined response Content-Type: text/html */*;charset=gbk]
-    expected: FAIL
-
   [<iframe>: combined response Content-Type: text/html;x=" text/plain]
     expected: FAIL
 
+  [<iframe>: combined response Content-Type: */* text/html]
+    expected: FAIL
+
+  [<iframe>: separate response Content-Type: text/html;" text/plain]
+    expected: FAIL
+
+  [<iframe>: separate response Content-Type: text/plain */*;charset=gbk]
+    expected: FAIL
+
diff --git a/tests/wpt/metadata/fetch/content-type/script.window.js.ini b/tests/wpt/metadata/fetch/content-type/script.window.js.ini
index 5c001592859..d2df9b78483 100644
--- a/tests/wpt/metadata/fetch/content-type/script.window.js.ini
+++ b/tests/wpt/metadata/fetch/content-type/script.window.js.ini
@@ -56,6 +56,3 @@
   [separate text/javascript x/x]
     expected: FAIL
 
-  [separate text/javascript;charset=windows-1252 error text/javascript]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini b/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini
index a63e414f43a..d4ba399b762 100644
--- a/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini
+++ b/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini
@@ -11,6 +11,6 @@
   [X-Content-Type-Options%3A%20nosniff%0C]
     expected: FAIL
 
-  [X-Content-Type-Options%3A%20%40%23%24%23%25%25%26%5E%26%5E*()()11!%2Cnosniff]
+  [X-Content-Type-Options%3A%20'NosniFF']
     expected: FAIL
 
diff --git a/tests/wpt/metadata/fetch/security/embedded-credentials.tentative.sub.html.ini b/tests/wpt/metadata/fetch/security/embedded-credentials.tentative.sub.html.ini
index ba7869a4741..07aac5f75f8 100644
--- a/tests/wpt/metadata/fetch/security/embedded-credentials.tentative.sub.html.ini
+++ b/tests/wpt/metadata/fetch/security/embedded-credentials.tentative.sub.html.ini
@@ -1,6 +1,6 @@
 [embedded-credentials.tentative.sub.html]
   type: testharness
-  expected: TIMEOUT
+  expected: CRASH
   [Embedded credentials are treated as network errors.]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_1.html.ini b/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_1.html.ini
new file mode 100644
index 00000000000..87b07c3e670
--- /dev/null
+++ b/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_1.html.ini
@@ -0,0 +1,4 @@
+[traverse_the_history_1.html]
+  [Multiple history traversals from the same task]
+    expected: FAIL
+
diff --git a/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/skip-document-with-fragment.html.ini b/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/skip-document-with-fragment.html.ini
index c12c0f8ae48..6852d7663de 100644
--- a/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/skip-document-with-fragment.html.ini
+++ b/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/skip-document-with-fragment.html.ini
@@ -1,4 +1,8 @@
 [skip-document-with-fragment.html]
+  expected: TIMEOUT
   [Autofocus elements in iframed documents with URL fragments should be skipped.]
     expected: FAIL
 
+  [Autofocus elements in top-level browsing context's documents with URI fragments should be skipped.]
+    expected: TIMEOUT
+
diff --git a/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/supported-elements.html.ini b/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/supported-elements.html.ini
index 6b68e9094e4..8b743f36e1d 100644
--- a/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/supported-elements.html.ini
+++ b/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/supported-elements.html.ini
@@ -1,16 +1,20 @@
 [supported-elements.html]
+  expected: TIMEOUT
   [Contenteditable element should support autofocus]
     expected: FAIL
 
   [Element with tabindex should support autofocus]
-    expected: FAIL
+    expected: TIMEOUT
 
   [Host element with delegatesFocus including no focusable descendants should be skipped]
-    expected: FAIL
+    expected: NOTRUN
 
   [Area element should support autofocus]
-    expected: FAIL
+    expected: NOTRUN
 
   [Host element with delegatesFocus should support autofocus]
-    expected: FAIL
+    expected: NOTRUN
+
+  [Non-HTMLElement should not support autofocus]
+    expected: NOTRUN
 
diff --git a/tests/wpt/metadata/resource-timing/crossorigin-sandwich-TAO.sub.html.ini b/tests/wpt/metadata/resource-timing/crossorigin-sandwich-TAO.sub.html.ini
index 1c7ec9ce1db..b4090ef9fe2 100644
--- a/tests/wpt/metadata/resource-timing/crossorigin-sandwich-TAO.sub.html.ini
+++ b/tests/wpt/metadata/resource-timing/crossorigin-sandwich-TAO.sub.html.ini
@@ -1,4 +1,5 @@
 [crossorigin-sandwich-TAO.sub.html]
+  expected: ERROR
   [There should be one entry.]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/webaudio/the-audio-api/the-analysernode-interface/realtimeanalyser-fft-scaling.html.ini b/tests/wpt/metadata/webaudio/the-audio-api/the-analysernode-interface/realtimeanalyser-fft-scaling.html.ini
index 66bd350083b..a56bad443a2 100644
--- a/tests/wpt/metadata/webaudio/the-audio-api/the-analysernode-interface/realtimeanalyser-fft-scaling.html.ini
+++ b/tests/wpt/metadata/webaudio/the-audio-api/the-analysernode-interface/realtimeanalyser-fft-scaling.html.ini
@@ -1,4 +1,5 @@
 [realtimeanalyser-fft-scaling.html]
+  expected: TIMEOUT
   [X 2048-point FFT peak position is not equal to 64. Got 0.]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/workers/semantics/multiple-workers/005.html.ini b/tests/wpt/metadata/workers/semantics/multiple-workers/005.html.ini
index f584fce5df1..268949ced5c 100644
--- a/tests/wpt/metadata/workers/semantics/multiple-workers/005.html.ini
+++ b/tests/wpt/metadata/workers/semantics/multiple-workers/005.html.ini
@@ -1,5 +1,4 @@
 [005.html]
-  expected: ERROR
   [dedicated worker in shared worker in dedicated worker]
     expected: FAIL
 
diff --git a/tests/wpt/web-platform-tests/loading/lazyload/move-element-and-scroll.tentative.html b/tests/wpt/web-platform-tests/loading/lazyload/move-element-and-scroll.tentative.html
new file mode 100644
index 00000000000..f9d89807b8c
--- /dev/null
+++ b/tests/wpt/web-platform-tests/loading/lazyload/move-element-and-scroll.tentative.html
@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<head>
+  <title>Images with loading='lazy' load being moved to another document
+         and then scrolled to</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="common.js"></script>
+</head>
+
+<!--
+Marked as tentative until https://github.com/whatwg/html/pull/3752 is landed.
+-->
+
+<body>
+  <div id="tall_div" style="height:1000vh"></div>
+  <div id="below_viewport_div"></div>
+  <img id="below_viewport" src='resources/image.png?below_viewport' loading="lazy">
+
+  <script>
+    const tall_div = document.getElementById("tall_div");
+    const below_viewport_element = document.getElementById("below_viewport");
+    const below_viewport_div = document.getElementById("below_viewport_div");
+
+    async_test(function(t) {
+      below_viewport_element.onload =
+        t.unreached_func("The below viewport image should not load");
+      t.step_timeout(t.step_func_done(), 1000);
+      const iframe = document.createElement('iframe');
+      iframe.setAttribute("style", "display:none");
+      iframe.srcdoc = "<body></body>";
+      iframe.onload = () => {
+        const adopted_img = iframe.contentDocument.adoptNode(below_viewport_element);
+        iframe.contentDocument.body.appendChild(adopted_img);
+        below_viewport_div.scrollIntoView();
+      };
+      document.body.insertBefore(iframe, tall_div);
+    }, "Test that <img> below viewport is not loaded when moved to another " +
+       "document and then scrolled to");
+</script>
+</body>
diff --git a/tests/wpt/web-platform-tests/loading/lazyload/remove-element-and-scroll.tentative.html b/tests/wpt/web-platform-tests/loading/lazyload/remove-element-and-scroll.tentative.html
new file mode 100644
index 00000000000..53708ceac75
--- /dev/null
+++ b/tests/wpt/web-platform-tests/loading/lazyload/remove-element-and-scroll.tentative.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<head>
+  <title>Images with loading='lazy' load being removed and then scrolled to</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="common.js"></script>
+</head>
+
+<!--
+Marked as tentative until https://github.com/whatwg/html/pull/3752 is landed.
+-->
+
+<body>
+  <img id="in_viewport" src='resources/image.png?in_viewport&pipe=trickle(d1)'>
+  <div style="height:1000vh"></div>
+  <div id="below_viewport_div"></div>
+  <img id="below_viewport" src='resources/image.png?below_viewport' loading="lazy">
+
+  <script>
+    const in_viewport_element = document.getElementById("in_viewport");
+    const below_viewport_element = document.getElementById("below_viewport");
+    const below_viewport_div = document.getElementById("below_viewport_div");
+
+    async_test(t => {
+      below_viewport_element.onload = t.unreached_func("Removed loading=lazy image " +
+        "should not load when its old position is scrolled to.");
+      below_viewport_element.remove();
+
+      in_viewport_element.onload = () => {
+        below_viewport_div.scrollIntoView();
+        t.step_timeout(t.step_func_done(), 2000);
+      };
+    }, "Test that <img> below viewport is not loaded when removed from the " +
+       "document and then scrolled to");
+  </script>
+</body>
diff --git a/tests/wpt/web-platform-tests/native-file-system/native_FileSystemWritableFileStream-piped.tentative.https.manual.window.js b/tests/wpt/web-platform-tests/native-file-system/native_FileSystemWritableFileStream-piped.tentative.https.manual.window.js
new file mode 100644
index 00000000000..2c0299df12e
--- /dev/null
+++ b/tests/wpt/web-platform-tests/native-file-system/native_FileSystemWritableFileStream-piped.tentative.https.manual.window.js
@@ -0,0 +1,4 @@
+// META: script=/resources/testdriver.js
+// META: script=resources/test-helpers.js
+// META: script=resources/native-fs-test-helpers.js
+// META: script=script-tests/FileSystemWritableFileStream-piped.js
diff --git a/tests/wpt/web-platform-tests/native-file-system/native_FileSystemWritableFileStream-write.tentative.https.manual.window.js b/tests/wpt/web-platform-tests/native-file-system/native_FileSystemWritableFileStream-write.tentative.https.manual.window.js
new file mode 100644
index 00000000000..0efacf9e607
--- /dev/null
+++ b/tests/wpt/web-platform-tests/native-file-system/native_FileSystemWritableFileStream-write.tentative.https.manual.window.js
@@ -0,0 +1,4 @@
+// META: script=/resources/testdriver.js
+// META: script=resources/test-helpers.js
+// META: script=resources/native-fs-test-helpers.js
+// META: script=script-tests/FileSystemWritableFileStream-write.js
diff --git a/tests/wpt/web-platform-tests/native-file-system/native_FileSystemWritableFileStream.tentative.https.manual.window.js b/tests/wpt/web-platform-tests/native-file-system/native_FileSystemWritableFileStream.tentative.https.manual.window.js
new file mode 100644
index 00000000000..caf6fbd1c52
--- /dev/null
+++ b/tests/wpt/web-platform-tests/native-file-system/native_FileSystemWritableFileStream.tentative.https.manual.window.js
@@ -0,0 +1,4 @@
+// META: script=/resources/testdriver.js
+// META: script=resources/test-helpers.js
+// META: script=resources/native-fs-test-helpers.js
+// META: script=script-tests/FileSystemWritableFileStream.js
diff --git a/tests/wpt/web-platform-tests/native-file-system/sandboxed_FileSystemWritableFileStream-piped.tentative.https.any.js b/tests/wpt/web-platform-tests/native-file-system/sandboxed_FileSystemWritableFileStream-piped.tentative.https.any.js
new file mode 100644
index 00000000000..eed6a561dc4
--- /dev/null
+++ b/tests/wpt/web-platform-tests/native-file-system/sandboxed_FileSystemWritableFileStream-piped.tentative.https.any.js
@@ -0,0 +1,4 @@
+// META: script=resources/test-helpers.js
+// META: script=resources/sandboxed-fs-test-helpers.js
+// META: script=../streams/resources/recording-streams.js
+// META: script=script-tests/FileSystemWritableFileStream-piped.js
diff --git a/tests/wpt/web-platform-tests/native-file-system/sandboxed_FileSystemWritableFileStream-write.tentative.https.any.js b/tests/wpt/web-platform-tests/native-file-system/sandboxed_FileSystemWritableFileStream-write.tentative.https.any.js
new file mode 100644
index 00000000000..7ef0ea0ef82
--- /dev/null
+++ b/tests/wpt/web-platform-tests/native-file-system/sandboxed_FileSystemWritableFileStream-write.tentative.https.any.js
@@ -0,0 +1,3 @@
+// META: script=resources/test-helpers.js
+// META: script=resources/sandboxed-fs-test-helpers.js
+// META: script=script-tests/FileSystemWritableFileStream-write.js
diff --git a/tests/wpt/web-platform-tests/native-file-system/sandboxed_FileSystemWritableFileStream.tentative.https.any.js b/tests/wpt/web-platform-tests/native-file-system/sandboxed_FileSystemWritableFileStream.tentative.https.any.js
new file mode 100644
index 00000000000..16dbbe6a808
--- /dev/null
+++ b/tests/wpt/web-platform-tests/native-file-system/sandboxed_FileSystemWritableFileStream.tentative.https.any.js
@@ -0,0 +1,3 @@
+// META: script=resources/test-helpers.js
+// META: script=resources/sandboxed-fs-test-helpers.js
+// META: script=script-tests/FileSystemWritableFileStream.js
diff --git a/tests/wpt/web-platform-tests/native-file-system/script-tests/FileSystemWritableFileStream-piped.js b/tests/wpt/web-platform-tests/native-file-system/script-tests/FileSystemWritableFileStream-piped.js
new file mode 100644
index 00000000000..59fc1e3d136
--- /dev/null
+++ b/tests/wpt/web-platform-tests/native-file-system/script-tests/FileSystemWritableFileStream-piped.js
@@ -0,0 +1,135 @@
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'foo_string.txt', root);
+  const wfs = await handle.createWritable();
+
+  const rs = recordingReadableStream({
+    start(controller) {
+      controller.enqueue('foo_string');
+      controller.close();
+    }
+  });
+
+  await rs.pipeTo(wfs, { preventCancel: true });
+  assert_equals(await getFileContents(handle), 'foo_string');
+  assert_equals(await getFileSize(handle), 10);
+}, 'can be piped to with a string');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'foo_arraybuf.txt', root);
+  const wfs = await handle.createWritable();
+  const buf = new ArrayBuffer(3);
+  const intView = new Uint8Array(buf);
+  intView[0] = 0x66;
+  intView[1] = 0x6f;
+  intView[2] = 0x6f;
+
+  const rs = recordingReadableStream({
+    start(controller) {
+      controller.enqueue(buf);
+      controller.close();
+    }
+  });
+
+  await rs.pipeTo(wfs, { preventCancel: true });
+  assert_equals(await getFileContents(handle), 'foo');
+  assert_equals(await getFileSize(handle), 3);
+}, 'can be piped to with an ArrayBuffer');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'foo_blob.txt', root);
+  const wfs = await handle.createWritable();
+
+  const rs = recordingReadableStream({
+    start(controller) {
+      controller.enqueue(new Blob(['foo']));
+      controller.close();
+    }
+  });
+
+  await rs.pipeTo(wfs, { preventCancel: true });
+  assert_equals(await getFileContents(handle), 'foo');
+  assert_equals(await getFileSize(handle), 3);
+}, 'can be piped to with a Blob');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'foo_write_param.txt', root);
+  const wfs = await handle.createWritable();
+
+  const rs = recordingReadableStream({
+    start(controller) {
+      controller.enqueue({type: 'write', data: 'foobar'});
+      controller.close();
+    }
+  });
+
+  await rs.pipeTo(wfs, { preventCancel: true });
+  assert_equals(await getFileContents(handle), 'foobar');
+  assert_equals(await getFileSize(handle), 6);
+}, 'can be piped to with a param object with write command');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'foo_write_param.txt', root);
+  const wfs = await handle.createWritable();
+
+  const rs = recordingReadableStream({
+    start(controller) {
+      controller.enqueue({type: 'write', data: 'foobar'});
+      controller.enqueue({type: 'truncate', size: 10});
+      controller.enqueue({type: 'write', position: 0, data: 'baz'});
+      controller.close();
+    }
+  });
+
+  await rs.pipeTo(wfs, { preventCancel: true });
+  assert_equals(await getFileContents(handle), 'bazbar\0\0\0\0');
+  assert_equals(await getFileSize(handle), 10);
+}, 'can be piped to with a param object with multiple commands');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'foo_write_queued.txt', root);
+  const wfs = await handle.createWritable();
+
+  const rs = recordingReadableStream({
+    start(controller) {
+      controller.enqueue('foo');
+      controller.enqueue('bar');
+      controller.enqueue('baz');
+      controller.close();
+    }
+  });
+
+  await rs.pipeTo(wfs, { preventCancel: true });
+  assert_equals(await getFileContents(handle), 'foobarbaz');
+  assert_equals(await getFileSize(handle), 9);
+}, 'multiple operations can be queued');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'fetched.txt', root);
+  const wfs = await handle.createWritable();
+
+  const response = await fetch('data:text/plain,fetched from far');
+  const body = await response.body;
+  await body.pipeTo(wfs, { preventCancel: true });
+  assert_equals(await getFileContents(handle), 'fetched from far');
+  assert_equals(await getFileSize(handle), 16);
+}, 'plays well with fetch');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'aborted should_be_empty.txt', root);
+  const wfs = await handle.createWritable();
+
+  const response = await fetch('data:text/plain,fetched from far');
+  const body = await response.body;
+
+  const abortController = new AbortController();
+  const signal = abortController.signal;
+
+  const promise = body.pipeTo(wfs, { signal });
+  await abortController.abort();
+
+  await promise_rejects(t, 'AbortError', promise, 'stream is aborted');
+  await promise_rejects(t, TypeError(), wfs.close(), 'stream cannot be closed to flush writes');
+
+  assert_equals(await getFileContents(handle), '');
+  assert_equals(await getFileSize(handle), 0);
+}, 'abort() aborts write');
diff --git a/tests/wpt/web-platform-tests/native-file-system/script-tests/FileSystemWritableFileStream-write.js b/tests/wpt/web-platform-tests/native-file-system/script-tests/FileSystemWritableFileStream-write.js
new file mode 100644
index 00000000000..f14d79fd040
--- /dev/null
+++ b/tests/wpt/web-platform-tests/native-file-system/script-tests/FileSystemWritableFileStream-write.js
@@ -0,0 +1,337 @@
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'empty_blob', root);
+  const stream = await handle.createWritable();
+
+  await stream.write(new Blob([]));
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '');
+  assert_equals(await getFileSize(handle), 0);
+}, 'write() with an empty blob to an empty file');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'valid_blob', root);
+  const stream = await handle.createWritable();
+
+  await stream.write(new Blob(['1234567890']));
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '1234567890');
+  assert_equals(await getFileSize(handle), 10);
+}, 'write() a blob to an empty file');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'write_param_empty', root);
+  const stream = await handle.createWritable();
+
+  await stream.write({type: 'write', data: '1234567890'});
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '1234567890');
+  assert_equals(await getFileSize(handle), 10);
+}, 'write() with WriteParams without position to an empty file');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'string_zero_offset', root);
+  const stream = await handle.createWritable();
+
+  await stream.write({type: 'write', position: 0, data: '1234567890'});
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '1234567890');
+  assert_equals(await getFileSize(handle), 10);
+}, 'write() a string to an empty file with zero offset');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'blob_zero_offset', root);
+  const stream = await handle.createWritable();
+
+  await stream.write({type: 'write', position: 0, data: new Blob(['1234567890'])});
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '1234567890');
+  assert_equals(await getFileSize(handle), 10);
+}, 'write() a blob to an empty file with zero offset');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'write_appends', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('12345');
+  await stream.write('67890');
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '1234567890');
+  assert_equals(await getFileSize(handle), 10);
+}, 'write() called consecutively appends');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'write_appends_object_string', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('12345');
+  await stream.write({type: 'write', data: '67890'});
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '1234567890');
+  assert_equals(await getFileSize(handle), 10);
+}, 'write() WriteParams without position and string appends');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'write_appends_object_blob', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('12345');
+  await stream.write({type: 'write', data: new Blob(['67890'])});
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '1234567890');
+  assert_equals(await getFileSize(handle), 10);
+}, 'write() WriteParams without position and blob appends');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'string_with_offset', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('1234567890');
+  await stream.write({type: 'write', position: 4, data: 'abc'});
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '1234abc890');
+  assert_equals(await getFileSize(handle), 10);
+}, 'write() called with a string and a valid offset');
+
+directory_test(async (t, root) => {
+const handle = await createEmptyFile(t, 'blob_with_offset', root);
+const stream = await handle.createWritable();
+
+await stream.write('1234567890');
+await stream.write({type: 'write', position: 4, data: new Blob(['abc'])});
+await stream.close();
+
+assert_equals(await getFileContents(handle), '1234abc890');
+assert_equals(await getFileSize(handle), 10);
+}, 'write() called with a blob and a valid offset');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'bad_offset', root);
+  const stream = await handle.createWritable();
+
+  await promise_rejects(
+      t, 'InvalidStateError', stream.write({type: 'write', position: 4, data: new Blob(['abc'])}));
+  await promise_rejects(
+      t, TypeError(), stream.close(), 'stream is already closed');
+
+  assert_equals(await getFileContents(handle), '');
+  assert_equals(await getFileSize(handle), 0);
+}, 'write() called with an invalid offset');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'empty_string', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('');
+  await stream.close();
+  assert_equals(await getFileContents(handle), '');
+  assert_equals(await getFileSize(handle), 0);
+}, 'write() with an empty string to an empty file');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'valid_utf8_string', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('foo🤘');
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'foo🤘');
+  assert_equals(await getFileSize(handle), 7);
+}, 'write() with a valid utf-8 string');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'string_with_unix_line_ending', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('foo\n');
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'foo\n');
+  assert_equals(await getFileSize(handle), 4);
+}, 'write() with a string with unix line ending preserved');
+
+directory_test(async (t, root) => {
+  const handle =
+      await createEmptyFile(t, 'string_with_windows_line_ending', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('foo\r\n');
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'foo\r\n');
+  assert_equals(await getFileSize(handle), 5);
+}, 'write() with a string with windows line ending preserved');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'empty_array_buffer', root);
+  const stream = await handle.createWritable();
+
+  const buf = new ArrayBuffer(0);
+  await stream.write(buf);
+  await stream.close();
+  assert_equals(await getFileContents(handle), '');
+  assert_equals(await getFileSize(handle), 0);
+}, 'write() with an empty array buffer to an empty file');
+
+directory_test(async (t, root) => {
+  const handle =
+      await createEmptyFile(t, 'valid_string_typed_byte_array', root);
+  const stream = await handle.createWritable();
+
+  const buf = new ArrayBuffer(3);
+  const intView = new Uint8Array(buf);
+  intView[0] = 0x66;
+  intView[1] = 0x6f;
+  intView[2] = 0x6f;
+  await stream.write(buf);
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'foo');
+  assert_equals(await getFileSize(handle), 3);
+}, 'write() with a valid typed array buffer');
+
+directory_test(async (t, root) => {
+  const dir = await createDirectory(t, 'parent_dir', root);
+  const file_name = 'close_fails_when_dir_removed.txt';
+  const handle = await createEmptyFile(t, file_name, dir);
+  const stream = await handle.createWritable();
+  await stream.write('foo');
+
+  await root.removeEntry('parent_dir', {recursive: true});
+  await promise_rejects(t, 'NotFoundError', stream.close());
+}, 'atomic writes: close() fails when parent directory is removed');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'atomic_writes.txt', root);
+  const stream = await handle.createWritable();
+  await stream.write('foox');
+
+  const stream2 = await handle.createWritable();
+  await stream2.write('bar');
+
+  assert_equals(await getFileSize(handle), 0);
+
+  await stream2.close();
+  assert_equals(await getFileContents(handle), 'bar');
+  assert_equals(await getFileSize(handle), 3);
+
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'foox');
+  assert_equals(await getFileSize(handle), 4);
+}, 'atomic writes: writable file streams make atomic changes on close');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'atomic_write_after_close.txt', root);
+  const stream = await handle.createWritable();
+  await stream.write('foo');
+
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'foo');
+  assert_equals(await getFileSize(handle), 3);
+
+  await promise_rejects(
+      t, TypeError(), stream.write('abc'));
+}, 'atomic writes: write() after close() fails');
+
+directory_test(async (t, root) => {
+  const handle =
+      await createEmptyFile(t, 'atomic_truncate_after_close.txt', root);
+  const stream = await handle.createWritable();
+  await stream.write('foo');
+
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'foo');
+  assert_equals(await getFileSize(handle), 3);
+
+  await promise_rejects(t, TypeError(), stream.truncate(0));
+}, 'atomic writes: truncate() after close() fails');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'atomic_close_after_close.txt', root);
+  const stream = await handle.createWritable();
+  await stream.write('foo');
+
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'foo');
+  assert_equals(await getFileSize(handle), 3);
+
+  await promise_rejects(t, TypeError(), stream.close());
+}, 'atomic writes: close() after close() fails');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'there_can_be_only_one.txt', root);
+  const stream = await handle.createWritable();
+  await stream.write('foo');
+
+  // This test might be flaky if there is a race condition allowing
+  // close() to be called multiple times.
+  const success_promises =
+      [...Array(100)].map(() => stream.close().then(() => 1).catch(() => 0));
+  const close_attempts = await Promise.all(success_promises);
+  const success_count = close_attempts.reduce((x, y) => x + y);
+  assert_equals(success_count, 1);
+}, 'atomic writes: only one close() operation may succeed');
+
+directory_test(async (t, root) => {
+  const dir = await createDirectory(t, 'parent_dir', root);
+  const file_name = 'atomic_writable_file_stream_persists_removed.txt';
+  const handle = await createFileWithContents(t, file_name, 'foo', dir);
+
+  const stream = await handle.createWritable();
+  await stream.write('bar');
+
+  await dir.removeEntry(file_name);
+  await promise_rejects(t, 'NotFoundError', getFileContents(handle));
+
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'bar');
+  assert_equals(await getFileSize(handle), 3);
+}, 'atomic writes: writable file stream persists file on close, even if file is removed');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'writer_written', root);
+  const stream = await handle.createWritable();
+  const writer = stream.getWriter();
+
+  await writer.write('foo');
+  await writer.write(new Blob(['bar']));
+  await writer.write({type: 'seek', position: 0});
+  await writer.write({type: 'write', data: 'baz'});
+  await writer.close();
+
+  assert_equals(await getFileContents(handle), 'bazbar');
+  assert_equals(await getFileSize(handle), 6);
+}, 'getWriter() can be used');
+
+directory_test(async (t, root) => {
+  const handle = await createFileWithContents(
+      t, 'content.txt', 'very long string', root);
+  const stream = await handle.createWritable();
+
+  await promise_rejects(
+      t, SyntaxError(), stream.write({type: 'truncate'}), 'truncate without size');
+
+}, 'WriteParams: truncate missing size param');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'content.txt', root);
+  const stream = await handle.createWritable();
+
+  await promise_rejects(
+      t, SyntaxError(), stream.write({type: 'write'}), 'write without data');
+
+}, 'WriteParams: write missing data param');
+
+directory_test(async (t, root) => {
+  const handle = await createFileWithContents(
+      t, 'content.txt', 'seekable', root);
+  const stream = await handle.createWritable();
+
+  await promise_rejects(
+      t, SyntaxError(), stream.write({type: 'seek'}), 'seek without position');
+
+}, 'WriteParams: seek missing position param');
diff --git a/tests/wpt/web-platform-tests/native-file-system/script-tests/FileSystemWritableFileStream.js b/tests/wpt/web-platform-tests/native-file-system/script-tests/FileSystemWritableFileStream.js
new file mode 100644
index 00000000000..5acf93aec8c
--- /dev/null
+++ b/tests/wpt/web-platform-tests/native-file-system/script-tests/FileSystemWritableFileStream.js
@@ -0,0 +1,117 @@
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'trunc_shrink', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('1234567890');
+  await stream.truncate(5);
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '12345');
+  assert_equals(await getFileSize(handle), 5);
+}, 'truncate() to shrink a file');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'trunc_grow', root);
+  const stream = await handle.createWritable();
+
+  await stream.write('abc');
+  await stream.truncate(5);
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), 'abc\0\0');
+  assert_equals(await getFileSize(handle), 5);
+}, 'truncate() to grow a file');
+
+directory_test(async (t, root) => {
+  const dir = await createDirectory(t, 'parent_dir', root);
+  const file_name = 'create_writable_fails_when_dir_removed.txt';
+  const handle = await createEmptyFile(t, file_name, dir);
+
+  await root.removeEntry('parent_dir', {recursive: true});
+  await promise_rejects(t, 'NotFoundError', handle.createWritable());
+}, 'createWritable() fails when parent directory is removed');
+
+directory_test(async (t, root) => {
+  const dir = await createDirectory(t, 'parent_dir', root);
+  const file_name = 'write_fails_when_dir_removed.txt';
+  const handle = await createEmptyFile(t, file_name, dir);
+  const stream = await handle.createWritable();
+
+  await root.removeEntry('parent_dir', {recursive: true});
+  await promise_rejects(t, 'NotFoundError', stream.write('foo'));
+}, 'write() fails when parent directory is removed');
+
+directory_test(async (t, root) => {
+  const dir = await createDirectory(t, 'parent_dir', root);
+  const file_name = 'truncate_fails_when_dir_removed.txt';
+  const handle = await createEmptyFile(t, file_name, dir);
+  const stream = await handle.createWritable();
+
+  await root.removeEntry('parent_dir', {recursive: true});
+  await promise_rejects(t, 'NotFoundError', stream.truncate(0));
+}, 'truncate() fails when parent directory is removed');
+
+directory_test(async (t, root) => {
+  const handle = await createFileWithContents(
+      t, 'atomic_file_is_copied.txt', 'fooks', root);
+  const stream = await handle.createWritable({keepExistingData: true});
+
+  await stream.write('bar');
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'barks');
+  assert_equals(await getFileSize(handle), 5);
+}, 'createWritable({keepExistingData: true}): atomic writable file stream initialized with source contents');
+
+directory_test(async (t, root) => {
+  const handle = await createFileWithContents(
+      t, 'atomic_file_is_not_copied.txt', 'very long string', root);
+  const stream = await handle.createWritable({keepExistingData: false});
+
+  await stream.write('bar');
+  assert_equals(await getFileContents(handle), 'very long string');
+  await stream.close();
+  assert_equals(await getFileContents(handle), 'bar');
+  assert_equals(await getFileSize(handle), 3);
+}, 'createWritable({keepExistingData: false}): atomic writable file stream initialized with empty file');
+
+directory_test(async (t, root) => {
+  const handle = await createFileWithContents(
+      t, 'trunc_smaller_offset.txt', '1234567890', root);
+  const stream = await handle.createWritable({keepExistingData: true});
+
+  await stream.truncate(5);
+  await stream.write('abc');
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), 'abc45');
+  assert_equals(await getFileSize(handle), 5);
+}, 'cursor position: truncate size > offset');
+
+directory_test(async (t, root) => {
+  const handle = await createFileWithContents(
+      t, 'trunc_bigger_offset.txt', '1234567890', root);
+  const stream = await handle.createWritable({keepExistingData: true});
+
+  await stream.seek(6);
+  await stream.truncate(5);
+  await stream.write('abc');
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), '12345abc');
+  assert_equals(await getFileSize(handle), 8);
+}, 'cursor position: truncate size < offset');
+
+directory_test(async (t, root) => {
+  const handle = await createEmptyFile(t, 'contents', root);
+  const stream = await handle.createWritable();
+
+  stream.write('abc');
+  stream.write('def');
+  stream.truncate(9);
+  stream.seek(0);
+  stream.write('xyz');
+  await stream.close();
+
+  assert_equals(await getFileContents(handle), 'xyzdef\0\0\0');
+  assert_equals(await getFileSize(handle), 9);
+}, 'commands are queued');
diff --git a/tests/wpt/web-platform-tests/tools/requirements_mypy.txt b/tests/wpt/web-platform-tests/tools/requirements_mypy.txt
index 50afed2bb2d..f3a56a6dd71 100644
--- a/tests/wpt/web-platform-tests/tools/requirements_mypy.txt
+++ b/tests/wpt/web-platform-tests/tools/requirements_mypy.txt
@@ -1,3 +1,3 @@
-mypy==0.760
+mypy==0.761
 mypy-extensions==0.4.3
 typed-ast==1.4.0
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/base.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/base.py
index 65534458197..fef052dd5ab 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/base.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/base.py
@@ -3,6 +3,7 @@ import platform
 import socket
 from abc import ABCMeta, abstractmethod
 from copy import deepcopy
+from six import iteritems
 
 from ..wptcommandline import require_arg  # noqa: F401
 
@@ -199,5 +200,5 @@ class ExecutorBrowser(object):
     up the browser from the runner process.
     """
     def __init__(self, **kwargs):
-        for k, v in kwargs.iteritems():
+        for k, v in iteritems(kwargs):
             setattr(self, k, v)
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/epiphany.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/epiphany.py
index 8a0e5f578b2..f6c4c602a38 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/epiphany.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/epiphany.py
@@ -2,7 +2,8 @@ from .base import get_timeout_multiplier, maybe_add_args, certificate_domain_lis
 from .webkit import WebKitBrowser
 from ..executors import executor_kwargs as base_executor_kwargs
 from ..executors.executorwebdriver import (WebDriverTestharnessExecutor,  # noqa: F401
-                                           WebDriverRefTestExecutor)  # noqa: F401
+                                           WebDriverRefTestExecutor,  # noqa: F401
+                                           WebDriverCrashtestExecutor)  # noqa: F401
 from ..executors.executorwebkit import WebKitDriverWdspecExecutor  # noqa: F401
 
 __wptrunner__ = {"product": "epiphany",
@@ -11,7 +12,8 @@ __wptrunner__ = {"product": "epiphany",
                  "browser_kwargs": "browser_kwargs",
                  "executor": {"testharness": "WebDriverTestharnessExecutor",
                               "reftest": "WebDriverRefTestExecutor",
-                              "wdspec": "WebKitDriverWdspecExecutor"},
+                              "wdspec": "WebKitDriverWdspecExecutor",
+                              "crashtest": "WebDriverCrashtestExecutor"},
                  "executor_kwargs": "executor_kwargs",
                  "env_extras": "env_extras",
                  "env_options": "env_options",
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/webkit.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/webkit.py
index aa286213945..1be683ed26e 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/webkit.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/webkit.py
@@ -2,7 +2,8 @@ from .base import Browser, ExecutorBrowser, require_arg
 from .base import get_timeout_multiplier, certificate_domain_list  # noqa: F401
 from ..executors import executor_kwargs as base_executor_kwargs
 from ..executors.executorwebdriver import (WebDriverTestharnessExecutor,  # noqa: F401
-                                           WebDriverRefTestExecutor)  # noqa: F401
+                                           WebDriverRefTestExecutor,  # noqa: F401
+                                           WebDriverCrashtestExecutor)  # noqa: F401
 from ..executors.executorwebkit import WebKitDriverWdspecExecutor  # noqa: F401
 from ..webdriver_server import WebKitDriverServer
 
@@ -13,7 +14,8 @@ __wptrunner__ = {"product": "webkit",
                  "browser_kwargs": "browser_kwargs",
                  "executor": {"testharness": "WebDriverTestharnessExecutor",
                               "reftest": "WebDriverRefTestExecutor",
-                              "wdspec": "WebKitDriverWdspecExecutor"},
+                              "wdspec": "WebKitDriverWdspecExecutor",
+                              "crashtest": "WebDriverCrashtestExecutor"},
                  "executor_kwargs": "executor_kwargs",
                  "env_extras": "env_extras",
                  "env_options": "env_options",
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/webkitgtk_minibrowser.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/webkitgtk_minibrowser.py
index d735f3c0792..d8b9744bd74 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/webkitgtk_minibrowser.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/webkitgtk_minibrowser.py
@@ -2,7 +2,8 @@ from .base import get_timeout_multiplier, maybe_add_args, certificate_domain_lis
 from .webkit import WebKitBrowser
 from ..executors import executor_kwargs as base_executor_kwargs
 from ..executors.executorwebdriver import (WebDriverTestharnessExecutor,  # noqa: F401
-                                           WebDriverRefTestExecutor)  # noqa: F401
+                                           WebDriverRefTestExecutor,  # noqa: F401
+                                           WebDriverCrashtestExecutor)  # noqa: F401
 from ..executors.executorwebkit import WebKitDriverWdspecExecutor  # noqa: F401
 
 __wptrunner__ = {"product": "webkitgtk_minibrowser",
@@ -11,7 +12,8 @@ __wptrunner__ = {"product": "webkitgtk_minibrowser",
                  "browser_kwargs": "browser_kwargs",
                  "executor": {"testharness": "WebDriverTestharnessExecutor",
                               "reftest": "WebDriverRefTestExecutor",
-                              "wdspec": "WebKitDriverWdspecExecutor"},
+                              "wdspec": "WebKitDriverWdspecExecutor",
+                              "crashtest": "WebDriverCrashtestExecutor"},
                  "executor_kwargs": "executor_kwargs",
                  "env_extras": "env_extras",
                  "env_options": "env_options",
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/environment.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/environment.py
index e79ae375064..7dcea4aeafa 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/environment.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/environment.py
@@ -5,6 +5,7 @@ import signal
 import socket
 import sys
 import time
+from six import iteritems
 
 from mozlog import get_default_logger, handlers, proxy
 
@@ -98,7 +99,7 @@ class TestEnvironment(object):
     def __exit__(self, exc_type, exc_val, exc_tb):
         self.process_interrupts()
 
-        for scheme, servers in self.servers.iteritems():
+        for scheme, servers in iteritems(self.servers):
             for port, server in servers:
                 server.kill()
         for cm in self.env_extras_cms:
@@ -194,7 +195,7 @@ class TestEnvironment(object):
         route_builder.add_handler(b"GET", b"/resources/testdriver.js",
                                   StringHandler(data, "text/javascript"))
 
-        for url_base, paths in self.test_paths.iteritems():
+        for url_base, paths in iteritems(self.test_paths):
             if url_base == "/":
                 continue
             route_builder.add_mount_point(url_base, paths["tests_path"])
@@ -220,7 +221,7 @@ class TestEnvironment(object):
     def test_servers(self):
         failed = []
         host = self.config["server_host"]
-        for scheme, servers in self.servers.iteritems():
+        for scheme, servers in iteritems(self.servers):
             for port, server in servers:
                 if self.test_server_port:
                     s = socket.socket()
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/executors/executorservo.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/executors/executorservo.py
index 9cef1fb2d7f..9eebfa59feb 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/executors/executorservo.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/executors/executorservo.py
@@ -7,6 +7,7 @@ import tempfile
 import threading
 import traceback
 import uuid
+from six import iteritems
 
 from mozprocess import ProcessHandler
 
@@ -45,7 +46,7 @@ def build_servo_command(test, test_url_func, browser, binary, pause_after_test,
         args += ["-Z", debug_opts]
     for stylesheet in browser.user_stylesheets:
         args += ["--user-stylesheet", stylesheet]
-    for pref, value in test.environment.get('prefs', {}).iteritems():
+    for pref, value in iteritems(test.environment.get('prefs', {})):
         args += ["--pref", "%s=%s" % (pref, value)]
     if browser.ca_certificate_path:
         args += ["--certificate-path", browser.ca_certificate_path]
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/expectedtree.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/expectedtree.py
index 4d505086bd8..7521f25b134 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/expectedtree.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/expectedtree.py
@@ -1,5 +1,6 @@
 from math import log
 from collections import defaultdict
+from six import iteritems, itervalues
 
 class Node(object):
     def __init__(self, prop, value):
@@ -33,7 +34,7 @@ def entropy(results):
 
     result_counts = defaultdict(int)
     total = float(len(results))
-    for values in results.itervalues():
+    for values in itervalues(results):
         # Not sure this is right, possibly want to treat multiple values as
         # distinct from multiple of the same value?
         for value in values:
@@ -41,7 +42,7 @@ def entropy(results):
 
     entropy_sum = 0
 
-    for count in result_counts.itervalues():
+    for count in itervalues(result_counts):
         prop = float(count) / total
         entropy_sum -= prop * log(prop, 2)
 
@@ -52,7 +53,7 @@ def split_results(prop, results):
     """Split a dictionary of results into a dictionary of dictionaries where
     each sub-dictionary has a specific value of the given property"""
     by_prop = defaultdict(dict)
-    for run_info, value in results.iteritems():
+    for run_info, value in iteritems(results):
         by_prop[run_info[prop]][run_info] = value
 
     return by_prop
@@ -77,13 +78,13 @@ def build_tree(properties, dependent_props, results, tree=None):
     prop_index = {prop: i for i, prop in enumerate(properties)}
 
     all_results = defaultdict(int)
-    for result_values in results.itervalues():
-        for result_value, count in result_values.iteritems():
+    for result_values in itervalues(results):
+        for result_value, count in iteritems(result_values):
             all_results[result_value] += count
 
     # If there is only one result we are done
     if not properties or len(all_results) == 1:
-        for value, count in all_results.iteritems():
+        for value, count in iteritems(all_results):
             tree.result_values[value] += count
         tree.run_info |= set(results.keys())
         return tree
@@ -99,7 +100,7 @@ def build_tree(properties, dependent_props, results, tree=None):
             continue
         new_entropy = 0.
         results_sets_entropy = []
-        for prop_value, result_set in result_sets.iteritems():
+        for prop_value, result_set in iteritems(result_sets):
             results_sets_entropy.append((entropy(result_set), prop_value, result_set))
             new_entropy += (float(len(result_set)) / len(results)) * results_sets_entropy[-1][0]
 
@@ -109,7 +110,7 @@ def build_tree(properties, dependent_props, results, tree=None):
 
     # In the case that no properties partition the space
     if not results_partitions:
-        for value, count in all_results.iteritems():
+        for value, count in iteritems(all_results):
             tree.result_values[value] += count
         tree.run_info |= set(results.keys())
         return tree
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestexpected.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestexpected.py
index eae85b1f666..65b53f0ab97 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestexpected.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestexpected.py
@@ -1,6 +1,7 @@
 import os
 from six.moves.urllib.parse import urljoin
 from collections import deque
+from six import text_type
 
 from .wptmanifest.backends import static
 from .wptmanifest.backends.base import ManifestItem
@@ -57,7 +58,7 @@ def tags(node):
     """Set of tags that have been applied to the test"""
     try:
         value = node.get("tags")
-        if isinstance(value, (str, unicode)):
+        if isinstance(value, text_type):
             return {value}
         return set(value)
     except KeyError:
@@ -66,7 +67,7 @@ def tags(node):
 
 def prefs(node):
     def value(ini_value):
-        if isinstance(ini_value, (str, unicode)):
+        if isinstance(ini_value, text_type):
             return tuple(pref_piece.strip() for pref_piece in ini_value.split(':', 1))
         else:
             # this should be things like @Reset, which are apparently type 'object'
@@ -74,7 +75,7 @@ def prefs(node):
 
     try:
         node_prefs = node.get("prefs")
-        if type(node_prefs) in (str, unicode):
+        if isinstance(node_prefs, text_type):
             rv = dict(value(node_prefs))
         else:
             rv = dict(value(item) for item in node_prefs)
@@ -86,7 +87,7 @@ def prefs(node):
 def set_prop(name, node):
     try:
         node_items = node.get(name)
-        if isinstance(node_items, (str, unicode)):
+        if isinstance(node_items, text_type):
             rv = {node_items}
         else:
             rv = set(node_items)
@@ -99,7 +100,7 @@ def leak_threshold(node):
     rv = {}
     try:
         node_items = node.get("leak-threshold")
-        if isinstance(node_items, (str, unicode)):
+        if isinstance(node_items, text_type):
             node_items = [node_items]
         for item in node_items:
             process, value = item.rsplit(":", 1)
@@ -156,7 +157,7 @@ def fuzzy_prop(node):
     if not isinstance(value, list):
         value = [value]
     for item in value:
-        if not isinstance(item, (str, unicode)):
+        if not isinstance(item, text_type):
             rv.append(item)
             continue
         parts = item.rsplit(":", 1)
@@ -478,7 +479,7 @@ def get_manifest(metadata_root, test_path, url_base, run_info):
     """
     manifest_path = expected.expected_path(metadata_root, test_path)
     try:
-        with open(manifest_path) as f:
+        with open(manifest_path, "rb") as f:
             return static.compile(f,
                                   run_info,
                                   data_cls_getter=data_cls_getter,
@@ -497,7 +498,7 @@ def get_dir_manifest(path, run_info):
                      values should be computed.
     """
     try:
-        with open(path) as f:
+        with open(path, "rb") as f:
             return static.compile(f,
                                   run_info,
                                   data_cls_getter=lambda x,y: DirectoryManifest)
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestinclude.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestinclude.py
index d302831a57a..b3ab2c07765 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestinclude.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestinclude.py
@@ -150,5 +150,5 @@ class IncludeManifest(ManifestItem):
 
 
 def get_manifest(manifest_path):
-    with open(manifest_path) as f:
+    with open(manifest_path, "rb") as f:
         return conditional.compile(f, data_cls_getter=lambda x, y: IncludeManifest)
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestupdate.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestupdate.py
index 2f2a8d54335..3cb1b510792 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestupdate.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/manifestupdate.py
@@ -3,7 +3,7 @@ import os
 from six.moves.urllib.parse import urljoin, urlsplit
 from collections import namedtuple, defaultdict, deque
 from math import ceil
-from six import iterkeys, itervalues, iteritems
+from six import integer_types, iterkeys, itervalues, iteritems, string_types, text_type
 
 from .wptmanifest import serialize
 from .wptmanifest.node import (DataNode, ConditionalNode, BinaryExpressionNode,
@@ -411,7 +411,7 @@ class PropertyUpdate(object):
         for e in errors:
             if disable_intermittent:
                 condition = e.cond.children[0] if e.cond else None
-                msg = disable_intermittent if isinstance(disable_intermittent, (str, unicode)) else "unstable"
+                msg = disable_intermittent if isinstance(disable_intermittent, string_types+(text_type,)) else "unstable"
                 self.node.set("disabled", msg, condition)
                 self.node.new_disabled = True
             else:
@@ -774,7 +774,7 @@ class AppendOnlyListUpdate(PropertyUpdate):
         for item in new:
             if item is None:
                 continue
-            elif isinstance(item, (str, unicode)):
+            elif isinstance(item, text_type):
                 rv.add(item)
             else:
                 rv |= item
@@ -897,10 +897,10 @@ def make_expr(prop_set, rhs):
 
 
 def make_node(value):
-    if type(value) in (int, float, long):
+    if isinstance(value, integer_types+(float,)):
         node = NumberNode(value)
-    elif type(value) in (str, unicode):
-        node = StringNode(unicode(value))
+    elif isinstance(value, text_type):
+        node = StringNode(text_type(value))
     elif hasattr(value, "__iter__"):
         node = ListNode()
         for item in value:
@@ -909,10 +909,10 @@ def make_node(value):
 
 
 def make_value_node(value):
-    if type(value) in (int, float, long):
+    if isinstance(value, integer_types+(float,)):
         node = ValueNode(value)
-    elif type(value) in (str, unicode):
-        node = ValueNode(unicode(value))
+    elif isinstance(value, text_type):
+        node = ValueNode(text_type(value))
     elif hasattr(value, "__iter__"):
         node = ListNode()
         for item in value:
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/metadata.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/metadata.py
index bf4d7a558ab..aafc7d52250 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/metadata.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/metadata.py
@@ -4,7 +4,7 @@ import os
 from collections import defaultdict, namedtuple
 
 from mozlog import structuredlog
-from six import itervalues
+from six import ensure_str, ensure_text, iteritems, iterkeys, itervalues, text_type
 from six.moves import intern
 
 from . import manifestupdate
@@ -44,11 +44,11 @@ class RunInfo(object):
         return self.canonical_repr == other.canonical_repr
 
     def iteritems(self):
-        for key, value in self.data.iteritems():
+        for key, value in iteritems(self.data):
             yield key, value
 
     def items(self):
-        return list(self.iteritems())
+        return list(iteritems(self))
 
 
 def update_expected(test_paths, serve_root, log_file_names,
@@ -239,7 +239,7 @@ def pack_result(data):
 def unpack_result(data):
     if isinstance(data, int):
         return (status_intern.get(data), None)
-    if isinstance(data, unicode):
+    if isinstance(data, text_type):
         return (data, None)
     # Unpack multiple statuses into a tuple to be used in the Results named tuple below,
     # separating `status` and `known_intermittent`.
@@ -289,7 +289,7 @@ def update_results(id_test_map,
     test_file_items = set(itervalues(id_test_map))
 
     default_expected_by_type = {}
-    for test_type, test_cls in wpttest.manifest_test_cls.iteritems():
+    for test_type, test_cls in iteritems(wpttest.manifest_test_cls):
         if test_cls.result_cls:
             default_expected_by_type[(test_type, False)] = test_cls.result_cls.default_expected
         if test_cls.subtest_result_cls:
@@ -427,7 +427,7 @@ class ExpectedUpdater(object):
             action_map["lsan_leak"](item)
 
         mozleak_data = data.get("mozleak", {})
-        for scope, scope_data in mozleak_data.iteritems():
+        for scope, scope_data in iteritems(mozleak_data):
             for key, action in [("objects", "mozleak_object"),
                                 ("total", "mozleak_total")]:
                 for item in scope_data.get(key, []):
@@ -439,7 +439,7 @@ class ExpectedUpdater(object):
         self.run_info = run_info_intern.store(RunInfo(data["run_info"]))
 
     def test_start(self, data):
-        test_id = intern(data["test"].encode("utf8"))
+        test_id = intern(ensure_str(data["test"]))
         try:
             self.id_test_map[test_id]
         except KeyError:
@@ -449,8 +449,8 @@ class ExpectedUpdater(object):
         self.tests_visited[test_id] = set()
 
     def test_status(self, data):
-        test_id = intern(data["test"].encode("utf8"))
-        subtest = intern(data["subtest"].encode("utf8"))
+        test_id = intern(ensure_str(data["test"]))
+        subtest = intern(ensure_str(data["subtest"]))
         test_data = self.id_test_map.get(test_id)
         if test_data is None:
             return
@@ -467,7 +467,7 @@ class ExpectedUpdater(object):
         if data["status"] == "SKIP":
             return
 
-        test_id = intern(data["test"].encode("utf8"))
+        test_id = intern(ensure_str(data["test"]))
         test_data = self.id_test_map.get(test_id)
         if test_data is None:
             return
@@ -480,7 +480,7 @@ class ExpectedUpdater(object):
         del self.tests_visited[test_id]
 
     def assertion_count(self, data):
-        test_id = intern(data["test"].encode("utf8"))
+        test_id = intern(ensure_str(data["test"]))
         test_data = self.id_test_map.get(test_id)
         if test_data is None:
             return
@@ -491,7 +491,7 @@ class ExpectedUpdater(object):
 
     def test_for_scope(self, data):
         dir_path = data.get("scope", "/")
-        dir_id = intern(os.path.join(dir_path, "__dir__").replace(os.path.sep, "/").encode("utf8"))
+        dir_id = intern(ensure_str(os.path.join(dir_path, "__dir__").replace(os.path.sep, "/")))
         if dir_id.startswith("/"):
             dir_id = dir_id[1:]
         return dir_id, self.id_test_map[dir_id]
@@ -530,13 +530,13 @@ def create_test_tree(metadata_path, test_manifest):
     assert all_types > exclude_types
     include_types = all_types - exclude_types
     for item_type, test_path, tests in test_manifest.itertypes(*include_types):
-        test_file_data = TestFileData(intern(test_manifest.url_base.encode("utf8")),
-                                      intern(item_type.encode("utf8")),
+        test_file_data = TestFileData(intern(ensure_str(test_manifest.url_base)),
+                                      intern(ensure_str(item_type)),
                                       metadata_path,
                                       test_path,
                                       tests)
         for test in tests:
-            id_test_map[intern(test.id.encode("utf8"))] = test_file_data
+            id_test_map[intern(ensure_str(test.id))] = test_file_data
 
         dir_path = os.path.split(test_path)[0].replace(os.path.sep, "/")
         while True:
@@ -544,9 +544,9 @@ def create_test_tree(metadata_path, test_manifest):
                 dir_id = dir_path + "/__dir__"
             else:
                 dir_id = "__dir__"
-            dir_id = intern((test_manifest.url_base + dir_id).lstrip("/").encode("utf8"))
+            dir_id = intern(ensure_str((test_manifest.url_base + dir_id).lstrip("/")))
             if dir_id not in id_test_map:
-                test_file_data = TestFileData(intern(test_manifest.url_base.encode("utf8")),
+                test_file_data = TestFileData(intern(ensure_str(test_manifest.url_base)),
                                               None,
                                               metadata_path,
                                               dir_id,
@@ -615,7 +615,7 @@ class TestFileData(object):
         self.item_type = item_type
         self.test_path = test_path
         self.metadata_path = metadata_path
-        self.tests = {intern(item.id.encode("utf8")) for item in tests}
+        self.tests = {intern(ensure_str(item.id)) for item in tests}
         self._requires_update = False
         self.data = defaultdict(lambda: defaultdict(PackedResultList))
 
@@ -656,11 +656,11 @@ class TestFileData(object):
         # Return subtest nodes present in the expected file, but missing from the data
         rv = []
 
-        for test_id, subtests in self.data.iteritems():
-            test = expected.get_test(test_id.decode("utf8"))
+        for test_id, subtests in iteritems(self.data):
+            test = expected.get_test(ensure_text(test_id))
             if not test:
                 continue
-            seen_subtests = set(item.decode("utf8") for item in subtests.iterkeys() if item is not None)
+            seen_subtests = set(ensure_text(item) for item in iterkeys(subtests) if item is not None)
             missing_subtests = set(test.subtests.keys()) - seen_subtests
             for item in missing_subtests:
                 expected_subtest = test.get_subtest(item)
@@ -729,9 +729,9 @@ class TestFileData(object):
             test_expected = expected.get_test(test_id)
             expected_by_test[test_id] = test_expected
 
-        for test_id, test_data in self.data.iteritems():
-            test_id = test_id.decode("utf8")
-            for subtest_id, results_list in test_data.iteritems():
+        for test_id, test_data in iteritems(self.data):
+            test_id = ensure_str(test_id)
+            for subtest_id, results_list in iteritems(test_data):
                 for prop, run_info, value in results_list:
                     # Special case directory metadata
                     if subtest_id is None and test_id.endswith("__dir__"):
@@ -747,8 +747,7 @@ class TestFileData(object):
                     if subtest_id is None:
                         item_expected = test_expected
                     else:
-                        if isinstance(subtest_id, str):
-                            subtest_id = subtest_id.decode("utf8")
+                        subtest_id = ensure_text(subtest_id)
                         item_expected = test_expected.get_subtest(subtest_id)
 
                     if prop == "status":
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/products.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/products.py
index e3117042709..abd84094bb3 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/products.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/products.py
@@ -1,5 +1,6 @@
 import importlib
 import imp
+from six import iteritems
 
 from .browsers import product_list
 
@@ -44,7 +45,7 @@ class Product(object):
         self.get_timeout_multiplier = getattr(module, data["timeout_multiplier"])
 
         self.executor_classes = {}
-        for test_type, cls_name in data["executor"].iteritems():
+        for test_type, cls_name in iteritems(data["executor"]):
             cls = getattr(module, cls_name)
             self.executor_classes[test_type] = cls
 
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/testloader.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/testloader.py
index fa54ca36157..f16cc14cead 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/testloader.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/testloader.py
@@ -5,6 +5,8 @@ from abc import ABCMeta, abstractmethod
 from six.moves.queue import Empty
 from collections import defaultdict, deque
 from multiprocessing import Queue
+from six import iteritems
+from six.moves import xrange
 
 from . import manifestinclude
 from . import manifestexpected
@@ -124,7 +126,7 @@ class ManifestLoader(object):
 
     def load(self):
         rv = {}
-        for url_base, paths in self.test_paths.iteritems():
+        for url_base, paths in iteritems(self.test_paths):
             manifest_file = self.load_manifest(url_base=url_base,
                                                **paths)
             path_data = {"url_base": url_base}
@@ -236,7 +238,7 @@ class TestLoader(object):
             manifest_items = self.chunker(manifest_items)
 
         for test_type, test_path, tests in manifest_items:
-            manifest_file = manifests_by_url_base[iter(tests).next().url_base]
+            manifest_file = manifests_by_url_base[next(iter(tests)).url_base]
             metadata_path = self.manifests[manifest_file]["metadata_path"]
 
             inherit_metadata, test_metadata = self.load_metadata(manifest_file, metadata_path, test_path)
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_expectedtree.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_expectedtree.py
index 2308be9590e..d71237a42da 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_expectedtree.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_expectedtree.py
@@ -1,7 +1,3 @@
-import sys
-
-import pytest
-
 from .. import expectedtree, metadata
 from collections import defaultdict
 
@@ -32,8 +28,6 @@ def results_object(results):
     return results_obj
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_build_tree_0():
     # Pass if debug
     results = [({"os": "linux", "version": "18.04", "debug": True}, "FAIL"),
@@ -53,8 +47,6 @@ def test_build_tree_0():
     assert dump_tree(tree) == expected
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_build_tree_1():
     # Pass if linux or windows 10
     results = [({"os": "linux", "version": "18.04", "debug": True}, "PASS"),
@@ -77,8 +69,6 @@ def test_build_tree_1():
     assert dump_tree(tree) == expected
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_build_tree_2():
     # Fails in a specific configuration
     results = [({"os": "linux", "version": "18.04", "debug": True}, "PASS"),
@@ -104,8 +94,6 @@ def test_build_tree_2():
     assert dump_tree(tree) == expected
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_build_tree_3():
 
     results = [({"os": "linux", "version": "18.04", "debug": True, "unused": False}, "PASS"),
@@ -118,8 +106,6 @@ def test_build_tree_3():
     assert dump_tree(tree) == expected
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_build_tree_4():
     # Check counts for multiple statuses
     results = [({"os": "linux", "version": "18.04", "debug": False}, "FAIL"),
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_manifestexpected.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_manifestexpected.py
index 525915d1832..f3e4ce796a4 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_manifestexpected.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_manifestexpected.py
@@ -1,4 +1,3 @@
-import sys
 from io import BytesIO
 
 import pytest
@@ -6,8 +5,6 @@ import pytest
 from .. import manifestexpected
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 @pytest.mark.parametrize("fuzzy, expected", [
     (b"ref.html:1;200", [("ref.html", ((1, 1), (200, 200)))]),
     (b"ref.html:0-1;100-200", [("ref.html", ((0, 1), (100, 200)))]),
@@ -25,7 +22,7 @@ from .. import manifestexpected
       ((u"test.html", u"ref1.html", "=="), ((5,10), (100, 100)))]),
 ])
 def test_fuzzy(fuzzy, expected):
-    data = """
+    data = b"""
 [test.html]
   fuzzy: %s""" % fuzzy
     f = BytesIO(data)
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_testloader.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_testloader.py
index e857cd43db6..836003d1060 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_testloader.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_testloader.py
@@ -20,8 +20,6 @@ skip: true
 
 @pytest.mark.xfail(sys.platform == "win32",
                    reason="NamedTemporaryFile cannot be reopened on Win32")
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="wptmanifest.parser doesn't support py3")
 def test_filter_unicode():
     tests = make_mock_manifest(("test", "a", 10), ("test", "a/b", 10),
                                ("test", "c", 10))
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_update.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_update.py
index 5ed36678806..a24e4a733da 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_update.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_update.py
@@ -108,7 +108,7 @@ def create_log(entries):
             getattr(logger, action)(**kwargs)
         logger.remove_handler(handler)
     else:
-        json.dump(entries, data)
+        data.write(json.dumps(entries).encode())
     data.seek(0)
     return data
 
@@ -132,11 +132,9 @@ def create_test_manifest(tests, url_base="/"):
     return m
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_0():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: FAIL""")]
 
@@ -154,11 +152,9 @@ def test_update_0():
     assert updated[0][1].is_empty
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_1():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: ERROR""")]
 
@@ -177,11 +173,9 @@ def test_update_1():
     assert new_manifest.get_test(test_id).children[0].get("expected", default_run_info) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_known_intermittent_1():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: PASS""")]
 
@@ -218,11 +212,9 @@ def test_update_known_intermittent_1():
         "expected", default_run_info) == ["PASS", "FAIL"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_known_intermittent_2():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: PASS""")]
 
@@ -243,11 +235,9 @@ def test_update_known_intermittent_2():
         "expected", default_run_info) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_existing_known_intermittent():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: [PASS, FAIL]""")]
 
@@ -286,11 +276,9 @@ def test_update_existing_known_intermittent():
         "expected", default_run_info) == ["PASS", "ERROR", "FAIL"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_remove_previous_intermittent():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: [PASS, FAIL]""")]
 
@@ -334,8 +322,6 @@ def test_update_remove_previous_intermittent():
         "expected", default_run_info) == ["PASS", "ERROR"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_new_test_with_intermittent():
     tests = [("path/to/test.htm", [test_id], "testharness", None)]
 
@@ -373,8 +359,6 @@ def test_update_new_test_with_intermittent():
         "expected", default_run_info) == ["PASS", "FAIL"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_expected_tie_resolution():
     tests = [("path/to/test.htm", [test_id], "testharness", None)]
 
@@ -402,11 +386,9 @@ def test_update_expected_tie_resolution():
         "expected", default_run_info) == ["PASS", "FAIL"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_reorder_expected():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: [PASS, FAIL]""")]
 
@@ -445,10 +427,8 @@ def test_update_reorder_expected():
         "expected", default_run_info) == ["FAIL", "PASS"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_and_preserve_unchanged_expected_intermittent():
-    tests = [("path/to/test.htm", [test_id], "testharness", """
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""
 [test.htm]
   expected:
     if os == "android": [PASS, FAIL]
@@ -488,11 +468,9 @@ def test_update_and_preserve_unchanged_expected_intermittent():
         "expected", default_run_info) == "PASS"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_test_with_intermittent_to_one_expected_status():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: [PASS, FAIL]""")]
 
@@ -513,10 +491,8 @@ def test_update_test_with_intermittent_to_one_expected_status():
         "expected", default_run_info) == "ERROR"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_intermittent_with_conditions():
-    tests = [("path/to/test.htm", [test_id], "testharness", """
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""
 [test.htm]
   expected:
     if os == "android": [PASS, FAIL]""")]
@@ -548,10 +524,8 @@ def test_update_intermittent_with_conditions():
         "expected", run_info_1) == ["PASS", "TIMEOUT", "FAIL"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_and_remove_intermittent_with_conditions():
-    tests = [("path/to/test.htm", [test_id], "testharness", """
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""
 [test.htm]
   expected:
     if os == "android": [PASS, FAIL]""")]
@@ -583,11 +557,9 @@ def test_update_and_remove_intermittent_with_conditions():
         "expected", run_info_1) == ["PASS", "TIMEOUT"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_intermittent_full():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected:
       if os == "mac": [FAIL, TIMEOUT]
@@ -623,11 +595,9 @@ def test_update_intermittent_full():
         "expected", default_run_info) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_intermittent_full_remove():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected:
       if os == "mac": [FAIL, TIMEOUT, PASS]
@@ -674,11 +644,9 @@ def test_update_intermittent_full_remove():
         "expected", default_run_info) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_full_update():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected:
       if os == "mac": [FAIL, TIMEOUT]
@@ -714,11 +682,9 @@ def test_full_update():
         "expected", default_run_info) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_full_orphan():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: FAIL
     [subsub test]
@@ -747,11 +713,9 @@ def test_full_orphan():
     assert len(new_manifest.get_test(test_id).children) == 1
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_reorder_expected_full_conditions():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected:
       if os == "mac": [FAIL, TIMEOUT]
@@ -808,11 +772,9 @@ def test_update_reorder_expected_full_conditions():
         "expected", default_run_info) == ["PASS", "FAIL"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_skip_0():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: FAIL""")]
 
@@ -828,10 +790,8 @@ def test_skip_0():
     assert not updated
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_new_subtest():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [test1]
     expected: FAIL""")]
 
@@ -853,10 +813,8 @@ def test_new_subtest():
     assert new_manifest.get_test(test_id).children[1].get("expected", default_run_info) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_multiple_0():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [test1]
     expected: FAIL""")]
 
@@ -892,10 +850,8 @@ def test_update_multiple_0():
         "expected", {"debug": False, "os": "linux"}) == "TIMEOUT"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_multiple_1():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [test1]
     expected: FAIL""")]
 
@@ -936,10 +892,8 @@ def test_update_multiple_1():
         "expected", run_info_3) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_multiple_2():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [test1]
     expected: FAIL""")]
 
@@ -976,10 +930,8 @@ def test_update_multiple_2():
         "expected", run_info_2) == "TIMEOUT"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_multiple_3():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [test1]
     expected:
       if debug: FAIL
@@ -1018,10 +970,8 @@ def test_update_multiple_3():
         "expected", run_info_2) == "TIMEOUT"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_ignore_existing():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [test1]
     expected:
       if debug: TIMEOUT
@@ -1060,8 +1010,6 @@ def test_update_ignore_existing():
         "expected", run_info_2) == "NOTRUN"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_new_test():
     tests = [("path/to/test.htm", [test_id], "testharness", None)]
 
@@ -1084,10 +1032,8 @@ def test_update_new_test():
         "expected", run_info_1) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_duplicate():
-    tests = [("path/to/test.htm", [test_id], "testharness", """
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""
 [test.htm]
   expected: ERROR""")]
 
@@ -1106,10 +1052,8 @@ def test_update_duplicate():
         "expected", run_info_1) == "ERROR"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_disable_intermittent():
-    tests = [("path/to/test.htm", [test_id], "testharness", """
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""
 [test.htm]
   expected: ERROR""")]
 
@@ -1128,10 +1072,8 @@ def test_update_disable_intermittent():
         "disabled", run_info_1) == "Some message"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_stability_conditional_instability():
-    tests = [("path/to/test.htm", [test_id], "testharness", """
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""
 [test.htm]
   expected: ERROR""")]
 
@@ -1164,10 +1106,8 @@ def test_update_stability_conditional_instability():
         "expected", run_info_2) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_full():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [test1]
     expected:
       if debug: TIMEOUT
@@ -1216,10 +1156,8 @@ def test_update_full():
         "expected", run_info_2) == "ERROR"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_full_unknown():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [test1]
     expected:
       if release_or_beta: ERROR
@@ -1259,10 +1197,8 @@ def test_update_full_unknown():
         "expected", run_info_2) == "ERROR"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_full_unknown_missing():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [subtest_deleted]
     expected:
       if release_or_beta: ERROR
@@ -1282,10 +1218,8 @@ def test_update_full_unknown_missing():
     assert len(updated) == 0
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_default():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   [test1]
     expected:
       if os == "mac": FAIL
@@ -1315,10 +1249,8 @@ def test_update_default():
     assert new_manifest.is_empty
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_default_1():
-    tests = [("path/to/test.htm", [test_id], "testharness", """
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""
 [test.htm]
   expected:
     if os == "mac": TIMEOUT
@@ -1347,10 +1279,8 @@ def test_update_default_1():
         "expected", run_info_2) == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_default_2():
-    tests = [("path/to/test.htm", [test_id], "testharness", """
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""
 [test.htm]
   expected:
     if os == "mac": TIMEOUT
@@ -1379,10 +1309,8 @@ def test_update_default_2():
         "expected", run_info_2) == "TIMEOUT"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_assertion_count_0():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   max-asserts: 4
   min-asserts: 2
 """)]
@@ -1403,10 +1331,8 @@ def test_update_assertion_count_0():
     assert new_manifest.get_test(test_id).get("min-asserts") == "2"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_assertion_count_1():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   max-asserts: 4
   min-asserts: 2
 """)]
@@ -1427,10 +1353,8 @@ def test_update_assertion_count_1():
     assert new_manifest.get_test(test_id).has_key("min-asserts") is False
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_assertion_count_2():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   max-asserts: 4
   min-asserts: 2
 """)]
@@ -1447,10 +1371,8 @@ def test_update_assertion_count_2():
     assert not updated
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_assertion_count_3():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]
   max-asserts: 4
   min-asserts: 2
 """)]
@@ -1481,10 +1403,8 @@ def test_update_assertion_count_3():
     assert new_manifest.get_test(test_id).get("min-asserts") == "2"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_assertion_count_4():
-    tests = [("path/to/test.htm", [test_id], "testharness", """[test.htm]""")]
+    tests = [("path/to/test.htm", [test_id], "testharness", b"""[test.htm]""")]
 
     log_0 = suite_log([("test_start", {"test": test_id}),
                        ("assertion_count", {"test": test_id,
@@ -1512,11 +1432,9 @@ def test_update_assertion_count_4():
     assert new_manifest.get_test(test_id).has_key("min-asserts") is False
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_lsan_0():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/to/__dir__", [dir_id], None, "")]
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/to/__dir__", [dir_id], None, b"")]
 
     log_0 = suite_log([("lsan_leak", {"scope": "path/to/",
                                       "frames": ["foo", "bar"]})])
@@ -1529,11 +1447,9 @@ def test_update_lsan_0():
     assert new_manifest.get("lsan-allowed") == ["foo"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_lsan_1():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/to/__dir__", [dir_id], None, """
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/to/__dir__", [dir_id], None, b"""
 lsan-allowed: [foo]""")]
 
     log_0 = suite_log([("lsan_leak", {"scope": "path/to/",
@@ -1549,13 +1465,11 @@ lsan-allowed: [foo]""")]
     assert new_manifest.get("lsan-allowed") == ["baz", "foo"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_lsan_2():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/__dir__", ["path/__dir__"], None, """
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/__dir__", ["path/__dir__"], None, b"""
 lsan-allowed: [foo]"""),
-             ("path/to/__dir__", [dir_id], None, "")]
+             ("path/to/__dir__", [dir_id], None, b"")]
 
     log_0 = suite_log([("lsan_leak", {"scope": "path/to/",
                                       "frames": ["foo", "bar"],
@@ -1571,11 +1485,9 @@ lsan-allowed: [foo]"""),
     assert new_manifest.get("lsan-allowed") == ["baz"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_lsan_3():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/to/__dir__", [dir_id], None, "")]
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/to/__dir__", [dir_id], None, b"")]
 
     log_0 = suite_log([("lsan_leak", {"scope": "path/to/",
                                       "frames": ["foo", "bar"]})],
@@ -1593,11 +1505,9 @@ def test_update_lsan_3():
     assert new_manifest.get("lsan-allowed") == ["baz", "foo"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_wptreport_0():
     tests = [("path/to/test.htm", [test_id], "testharness",
-              """[test.htm]
+              b"""[test.htm]
   [test1]
     expected: FAIL""")]
 
@@ -1615,11 +1525,9 @@ def test_update_wptreport_0():
     assert updated[0][1].is_empty
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_wptreport_1():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/to/__dir__", [dir_id], None, "")]
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/to/__dir__", [dir_id], None, b"")]
 
     log = {"run_info": default_run_info.copy(),
            "results": [],
@@ -1632,11 +1540,9 @@ def test_update_wptreport_1():
     assert updated[0][1].get("lsan-allowed") == ["baz"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_leak_total_0():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/to/__dir__", [dir_id], None, "")]
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/to/__dir__", [dir_id], None, b"")]
 
     log_0 = suite_log([("mozleak_total", {"scope": "path/to/",
                                           "process": "default",
@@ -1651,11 +1557,9 @@ def test_update_leak_total_0():
     assert new_manifest.get("leak-threshold") == ['default:51200']
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_leak_total_1():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/to/__dir__", [dir_id], None, "")]
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/to/__dir__", [dir_id], None, b"")]
 
     log_0 = suite_log([("mozleak_total", {"scope": "path/to/",
                                           "process": "default",
@@ -1667,11 +1571,9 @@ def test_update_leak_total_1():
     assert not updated
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_leak_total_2():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/to/__dir__", [dir_id], None, """
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/to/__dir__", [dir_id], None, b"""
 leak-total: 110""")]
 
     log_0 = suite_log([("mozleak_total", {"scope": "path/to/",
@@ -1684,11 +1586,9 @@ leak-total: 110""")]
     assert not updated
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_leak_total_3():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/to/__dir__", [dir_id], None, """
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/to/__dir__", [dir_id], None, b"""
 leak-total: 100""")]
 
     log_0 = suite_log([("mozleak_total", {"scope": "path/to/",
@@ -1704,11 +1604,9 @@ leak-total: 100""")]
     assert new_manifest.get("leak-threshold") == ['default:51200']
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="metadata doesn't support py3")
 def test_update_leak_total_4():
-    tests = [("path/to/test.htm", [test_id], "testharness", ""),
-             ("path/to/__dir__", [dir_id], None, """
+    tests = [("path/to/test.htm", [test_id], "testharness", b""),
+             ("path/to/__dir__", [dir_id], None, b"""
 leak-total: 110""")]
 
     log_0 = suite_log([
@@ -1737,8 +1635,6 @@ class UpdateRunner(StepRunner):
     steps = [TestStep]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="update.state doesn't support py3")
 def test_update_pickle():
     logger = structuredlog.StructuredLogger("expected_test")
     args = {
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_wpttest.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_wpttest.py
index 9bb3e1fd34e..1a94a2f3303 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_wpttest.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/tests/test_wpttest.py
@@ -1,5 +1,3 @@
-import pytest
-import sys
 from io import BytesIO
 from mock import Mock
 
@@ -7,29 +5,29 @@ from manifest import manifest as wptmanifest
 from manifest.item import TestharnessTest
 from .. import manifestexpected, wpttest
 
-dir_ini_0 = """\
+dir_ini_0 = b"""\
 prefs: [a:b]
 """
 
-dir_ini_1 = """\
+dir_ini_1 = b"""\
 prefs: [@Reset, b:c]
 max-asserts: 2
 min-asserts: 1
 tags: [b, c]
 """
 
-dir_ini_2 = """\
+dir_ini_2 = b"""\
 lsan-max-stack-depth: 42
 """
 
-test_0 = """\
+test_0 = b"""\
 [0.html]
   prefs: [c:d]
   max-asserts: 3
   tags: [a, @Reset]
 """
 
-test_1 = """\
+test_1 = b"""\
 [1.html]
   prefs:
     if os == 'win': [a:b, c:d]
@@ -37,12 +35,12 @@ test_1 = """\
     if os == 'win': FAIL
 """
 
-test_2 = """\
+test_2 = b"""\
 [2.html]
   lsan-max-stack-depth: 42
 """
 
-test_3 = """\
+test_3 = b"""\
 [3.html]
   [subtest1]
     expected: [PASS, FAIL]
@@ -54,32 +52,32 @@ test_3 = """\
     expected: FAIL
 """
 
-test_4 = """\
+test_4 = b"""\
 [4.html]
   expected: FAIL
 """
 
-test_5 = """\
+test_5 = b"""\
 [5.html]
 """
 
-test_6 = """\
+test_6 = b"""\
 [6.html]
   expected: [OK, FAIL]
 """
 
-test_7 = """\
+test_7 = b"""\
 [7.html]
   blink_expect_any_subtest_status: yep
 """
 
-test_fuzzy = """\
+test_fuzzy = b"""\
 [fuzzy.html]
   fuzzy: fuzzy-ref.html:1;200
 """
 
 
-testharness_test = """<script src="/resources/testharness.js"></script>
+testharness_test = b"""<script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>"""
 
 
@@ -117,8 +115,6 @@ def make_test_object(test_name,
     return wpttest.from_manifest(tests, test, inherit_metadata, test_metadata.get_test(test.id))
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 def test_metadata_inherit():
     items = [("test", "a", 10), ("test", "a/b", 10), ("test", "c", 10)]
     inherit_metadata = [
@@ -136,8 +132,6 @@ def test_metadata_inherit():
     assert test_obj.tags == {"a", "dir:a"}
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 def test_conditional():
     items = [("test", "a", 10), ("test", "a/b", 10), ("test", "c", 10)]
 
@@ -147,8 +141,6 @@ def test_conditional():
     assert test_obj.expected() == "FAIL"
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 def test_metadata_lsan_stack_depth():
     items = [("test", "a", 10), ("test", "a/b", 10)]
 
@@ -172,8 +164,6 @@ def test_metadata_lsan_stack_depth():
     assert test_obj.lsan_max_stack_depth == 42
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 def test_subtests():
     test_obj = make_test_object(test_3, "a/3.html", 3, ("test", "a", 4), None, False)
     assert test_obj.expected("subtest1") == "PASS"
@@ -184,40 +174,30 @@ def test_subtests():
     assert test_obj.known_intermittent("subtest3") == []
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 def test_expected_fail():
     test_obj = make_test_object(test_4, "a/4.html", 4, ("test", "a", 5), None, False)
     assert test_obj.expected() == "FAIL"
     assert test_obj.known_intermittent() == []
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 def test_no_expected():
     test_obj = make_test_object(test_5, "a/5.html", 5, ("test", "a", 6), None, False)
     assert test_obj.expected() == "OK"
     assert test_obj.known_intermittent() == []
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 def test_known_intermittent():
     test_obj = make_test_object(test_6, "a/6.html", 6, ("test", "a", 7), None, False)
     assert test_obj.expected() == "OK"
     assert test_obj.known_intermittent() == ["FAIL"]
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 def test_expect_any_subtest_status():
     test_obj = make_test_object(test_7, "a/7.html", 7, ("test", "a", 8), None, False)
     assert test_obj.expected() == "OK"
     assert test_obj.expect_any_subtest_status() is True
 
 
-@pytest.mark.xfail(sys.version[0] == "3",
-                   reason="bytes/text confusion in py3")
 def test_metadata_fuzzy():
     manifest_data = {
         "items": {"reftest": {"a/fuzzy.html": [["a/fuzzy.html",
@@ -234,7 +214,7 @@ def test_metadata_fuzzy():
                                                     test_path="a/fuzzy.html",
                                                     url_base="/")
 
-    test = manifest.iterpath("a/fuzzy.html").next()
+    test = next(manifest.iterpath("a/fuzzy.html"))
     test_obj = wpttest.from_manifest(manifest, test, [], test_metadata.get_test(test.id))
 
     assert test_obj.fuzzy == {('/a/fuzzy.html', '/a/fuzzy-ref.html', '=='): [[2, 3], [10, 15]]}
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/update/state.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/update/state.py
index 64dbf118060..f8a83525cbd 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/update/state.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/update/state.py
@@ -11,7 +11,7 @@ class BaseState(object):
             return rv
 
         logger.debug("No existing state found")
-        return object.__new__(cls, logger)
+        return super(BaseState, cls).__new__(cls)
 
     def __init__(self, logger):
         """Object containing state variables created when running Steps.
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptcommandline.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptcommandline.py
index 923bdaa5585..91f1161b01b 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptcommandline.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptcommandline.py
@@ -37,7 +37,7 @@ def require_arg(kwargs, name, value_func=None):
 def create_parser(product_choices=None):
     from mozlog import commandline
 
-    import products
+    from . import products
 
     if product_choices is None:
         config_data = config.load()
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptlogging.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptlogging.py
index 69cee744879..444d1d962d2 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptlogging.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptlogging.py
@@ -14,7 +14,7 @@ def setup(args, defaults, formatter_defaults=None):
                                            formatter_defaults=formatter_defaults)
     setup_stdlib_logger()
 
-    for name in args.keys():
+    for name in list(args.keys()):
         if name.startswith("log_"):
             args.pop(name)
 
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptrunner.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptrunner.py
index cac172a5940..7409dc26560 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptrunner.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wptrunner.py
@@ -3,19 +3,20 @@ from __future__ import print_function, unicode_literals
 import json
 import os
 import sys
+from six import iteritems, itervalues
 
 from wptserve import sslutils
 
-import environment as env
-import products
-import testloader
-import wptcommandline
-import wptlogging
-import wpttest
+from . import environment as env
+from . import products
+from . import testloader
+from . import wptcommandline
+from . import wptlogging
+from . import wpttest
 from mozlog import capture, handlers
-from font import FontInstaller
-from testrunner import ManagerGroup
-from browsers.base import NullBrowser
+from .font import FontInstaller
+from .testrunner import ManagerGroup
+from .browsers.base import NullBrowser
 
 here = os.path.split(__file__)[0]
 
@@ -102,7 +103,7 @@ def list_disabled(test_paths, product, **kwargs):
     run_info, test_loader = get_loader(test_paths, product,
                                        run_info_extras=run_info_extras, **kwargs)
 
-    for test_type, tests in test_loader.disabled_tests.iteritems():
+    for test_type, tests in iteritems(test_loader.disabled_tests):
         for test in tests:
             rv.append({"test": test.id, "reason": test.disabled()})
     print(json.dumps(rv, indent=2))
@@ -127,7 +128,7 @@ def get_pause_after_test(test_loader, **kwargs):
         if kwargs["headless"]:
             return False
         tests = test_loader.tests
-        is_single_testharness = (sum(len(item) for item in tests.itervalues()) == 1 and
+        is_single_testharness = (sum(len(item) for item in itervalues(tests)) == 1 and
                                  len(tests.get("testharness", [])) == 1)
         if kwargs["repeat"] == 1 and kwargs["rerun"] == 1 and is_single_testharness:
             return True
diff --git a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wpttest.py b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wpttest.py
index 67b57583424..4cbaedcdb01 100644
--- a/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wpttest.py
+++ b/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/wpttest.py
@@ -2,6 +2,7 @@ import os
 import subprocess
 from six.moves.urllib.parse import urljoin
 from collections import defaultdict
+from six import string_types
 
 from .wptmanifest.parser import atoms
 
@@ -337,7 +338,7 @@ class Test(object):
 
         try:
             expected = metadata.get("expected")
-            if isinstance(expected, (basestring)):
+            if isinstance(expected, string_types):
                 return expected
             elif isinstance(expected, list):
                 return expected[0]
diff --git a/tests/wpt/web-platform-tests/wasm/jsapi/constructor/multi-value.any.js b/tests/wpt/web-platform-tests/wasm/jsapi/constructor/multi-value.any.js
index 7fbac5b24f1..2c53e3611e0 100644
--- a/tests/wpt/web-platform-tests/wasm/jsapi/constructor/multi-value.any.js
+++ b/tests/wpt/web-platform-tests/wasm/jsapi/constructor/multi-value.any.js
@@ -10,8 +10,8 @@ promise_test(async () => {
   builder
     .addFunction("swap", type_if_fi)
     .addBody([
-        kExprGetLocal, 1,
-        kExprGetLocal, 0,
+        kExprLocalGet, 1,
+        kExprLocalGet, 0,
         kExprReturn,
     ])
     .exportFunc();
@@ -31,8 +31,8 @@ promise_test(async () => {
   const swap = builder
     .addFunction("swap", type_if_fi)
     .addBody([
-        kExprGetLocal, 1,
-        kExprGetLocal, 0,
+        kExprLocalGet, 1,
+        kExprLocalGet, 0,
         kExprReturn,
     ]);
   builder
diff --git a/tests/wpt/web-platform-tests/wasm/jsapi/instanceTestFactory.js b/tests/wpt/web-platform-tests/wasm/jsapi/instanceTestFactory.js
index 7ccf06c234a..c81672f208b 100644
--- a/tests/wpt/web-platform-tests/wasm/jsapi/instanceTestFactory.js
+++ b/tests/wpt/web-platform-tests/wasm/jsapi/instanceTestFactory.js
@@ -183,7 +183,7 @@ const instanceTestFactory = [
       builder
         .addFunction("fn", kSig_i_v)
         .addBody([
-            kExprGetGlobal,
+            kExprGlobalGet,
             index,
             kExprReturn,
         ])
diff --git a/tests/wpt/web-platform-tests/wasm/jsapi/module/customSections.any.js b/tests/wpt/web-platform-tests/wasm/jsapi/module/customSections.any.js
index 8e9732e5512..09355979d84 100644
--- a/tests/wpt/web-platform-tests/wasm/jsapi/module/customSections.any.js
+++ b/tests/wpt/web-platform-tests/wasm/jsapi/module/customSections.any.js
@@ -81,22 +81,10 @@ test(() => {
   const bytes1 = [87, 101, 98, 65, 115, 115, 101, 109, 98, 108, 121];
   const bytes2 = [74, 83, 65, 80, 73];
 
-  const binary = new Binary;
-  binary.emit_section(kUnknownSectionCode, section => {
-    section.emit_string("name");
-    section.emit_bytes(bytes1);
-  });
-  binary.emit_section(kUnknownSectionCode, section => {
-    section.emit_string("name");
-    section.emit_bytes(bytes2);
-  });
-  binary.emit_section(kUnknownSectionCode, section => {
-    section.emit_string("foo");
-    section.emit_bytes(bytes1);
-  });
-
   const builder = new WasmModuleBuilder();
-  builder.addExplicitSection(binary.trunc_buffer());
+  builder.addCustomSection("name", bytes1);
+  builder.addCustomSection("name", bytes2);
+  builder.addCustomSection("foo", bytes1);
   const buffer = builder.toBuffer()
   const module = new WebAssembly.Module(buffer);
 
@@ -119,14 +107,8 @@ test(() => {
   const bytes = [87, 101, 98, 65, 115, 115, 101, 109, 98, 108, 121];
   const name = "yee\uD801\uDC37eey"
 
-  const binary = new Binary;
-  binary.emit_section(kUnknownSectionCode, section => {
-    section.emit_string(name);
-    section.emit_bytes(bytes);
-  });
-
   const builder = new WasmModuleBuilder();
-  builder.addExplicitSection(binary.trunc_buffer());
+  builder.addCustomSection(name, bytes);
   const buffer = builder.toBuffer();
   const module = new WebAssembly.Module(buffer);
 
@@ -140,14 +122,8 @@ test(() => {
 test(() => {
   const bytes = [87, 101, 98, 65, 115, 115, 101, 109, 98, 108, 121];
 
-  const binary = new Binary;
-  binary.emit_section(kUnknownSectionCode, section => {
-    section.emit_string("na\uFFFDme");
-    section.emit_bytes(bytes);
-  });
-
   const builder = new WasmModuleBuilder();
-  builder.addExplicitSection(binary.trunc_buffer());
+  builder.addCustomSection("na\uFFFDme", bytes);
   const buffer = builder.toBuffer();
   const module = new WebAssembly.Module(buffer);
 
diff --git a/tests/wpt/web-platform-tests/wasm/jsapi/wasm-module-builder.js b/tests/wpt/web-platform-tests/wasm/jsapi/wasm-module-builder.js
index 09ff891f52e..82c6e04135f 100644
--- a/tests/wpt/web-platform-tests/wasm/jsapi/wasm-module-builder.js
+++ b/tests/wpt/web-platform-tests/wasm/jsapi/wasm-module-builder.js
@@ -66,6 +66,8 @@ let kStartSectionCode = 8;       // Start function declaration
 let kElementSectionCode = 9;     // Elements section
 let kCodeSectionCode = 10;       // Function code
 let kDataSectionCode = 11;       // Data segments
+let kDataCountSectionCode = 12;  // Data segment count (between Element & Code)
+let kExceptionSectionCode = 13;  // Exception section (between Global & Export)
 
 // Name section types
 let kModuleNameCode = 0;
@@ -76,7 +78,13 @@ let kWasmFunctionTypeForm = 0x60;
 let kWasmAnyFunctionTypeForm = 0x70;
 
 let kHasMaximumFlag = 1;
-let kResizableMaximumFlag = 1;
+let kSharedHasMaximumFlag = 3;
+
+// Segment flags
+let kActiveNoIndex = 0;
+let kPassive = 1;
+let kActiveWithIndex = 2;
+let kPassiveWithElements = 5;
 
 // Function declaration flags
 let kDeclFunctionName   = 0x01;
@@ -91,14 +99,21 @@ let kWasmI64 = 0x7e;
 let kWasmF32 = 0x7d;
 let kWasmF64 = 0x7c;
 let kWasmS128 = 0x7b;
+let kWasmAnyRef = 0x6f;
+let kWasmAnyFunc = 0x70;
+let kWasmExnRef = 0x68;
 
 let kExternalFunction = 0;
 let kExternalTable = 1;
 let kExternalMemory = 2;
 let kExternalGlobal = 3;
+let kExternalException = 4;
 
 let kTableZero = 0;
 let kMemoryZero = 0;
+let kSegmentZero = 0;
+
+let kExceptionAttribute = 0;
 
 // Useful signatures
 let kSig_i_i = makeSig([kWasmI32], [kWasmI32]);
@@ -123,11 +138,30 @@ let kSig_v_l = makeSig([kWasmI64], []);
 let kSig_v_d = makeSig([kWasmF64], []);
 let kSig_v_dd = makeSig([kWasmF64, kWasmF64], []);
 let kSig_v_ddi = makeSig([kWasmF64, kWasmF64, kWasmI32], []);
+let kSig_ii_v = makeSig([], [kWasmI32, kWasmI32]);
+let kSig_iii_v = makeSig([], [kWasmI32, kWasmI32, kWasmI32]);
+let kSig_ii_i = makeSig([kWasmI32], [kWasmI32, kWasmI32]);
+let kSig_iii_i = makeSig([kWasmI32], [kWasmI32, kWasmI32, kWasmI32]);
+let kSig_ii_ii = makeSig([kWasmI32, kWasmI32], [kWasmI32, kWasmI32]);
+let kSig_iii_ii = makeSig([kWasmI32, kWasmI32], [kWasmI32, kWasmI32, kWasmI32]);
 
 let kSig_v_f = makeSig([kWasmF32], []);
 let kSig_f_f = makeSig([kWasmF32], [kWasmF32]);
 let kSig_f_d = makeSig([kWasmF64], [kWasmF32]);
 let kSig_d_d = makeSig([kWasmF64], [kWasmF64]);
+let kSig_r_r = makeSig([kWasmAnyRef], [kWasmAnyRef]);
+let kSig_a_a = makeSig([kWasmAnyFunc], [kWasmAnyFunc]);
+let kSig_e_e = makeSig([kWasmExnRef], [kWasmExnRef]);
+let kSig_i_r = makeSig([kWasmAnyRef], [kWasmI32]);
+let kSig_v_r = makeSig([kWasmAnyRef], []);
+let kSig_v_a = makeSig([kWasmAnyFunc], []);
+let kSig_v_e = makeSig([kWasmExnRef], []);
+let kSig_v_rr = makeSig([kWasmAnyRef, kWasmAnyRef], []);
+let kSig_v_aa = makeSig([kWasmAnyFunc, kWasmAnyFunc], []);
+let kSig_r_v = makeSig([], [kWasmAnyRef]);
+let kSig_a_v = makeSig([], [kWasmAnyFunc]);
+let kSig_a_i = makeSig([kWasmI32], [kWasmAnyFunc]);
+let kSig_e_v = makeSig([], [kWasmExnRef]);
 
 function makeSig(params, results) {
   return {params: params, results: results};
@@ -163,6 +197,8 @@ let kExprElse = 0x05;
 let kExprTry = 0x06;
 let kExprCatch = 0x07;
 let kExprThrow = 0x08;
+let kExprRethrow = 0x09;
+let kExprBrOnExn = 0x0a;
 let kExprEnd = 0x0b;
 let kExprBr = 0x0c;
 let kExprBrIf = 0x0d;
@@ -170,13 +206,17 @@ let kExprBrTable = 0x0e;
 let kExprReturn = 0x0f;
 let kExprCallFunction = 0x10;
 let kExprCallIndirect = 0x11;
+let kExprReturnCall = 0x12;
+let kExprReturnCallIndirect = 0x13;
 let kExprDrop = 0x1a;
 let kExprSelect = 0x1b;
-let kExprGetLocal = 0x20;
-let kExprSetLocal = 0x21;
-let kExprTeeLocal = 0x22;
-let kExprGetGlobal = 0x23;
-let kExprSetGlobal = 0x24;
+let kExprLocalGet = 0x20;
+let kExprLocalSet = 0x21;
+let kExprLocalTee = 0x22;
+let kExprGlobalGet = 0x23;
+let kExprGlobalSet = 0x24;
+let kExprTableGet = 0x25;
+let kExprTableSet = 0x26;
 let kExprI32LoadMem = 0x28;
 let kExprI64LoadMem = 0x29;
 let kExprF32LoadMem = 0x2a;
@@ -329,6 +369,108 @@ let kExprI32ReinterpretF32 = 0xbc;
 let kExprI64ReinterpretF64 = 0xbd;
 let kExprF32ReinterpretI32 = 0xbe;
 let kExprF64ReinterpretI64 = 0xbf;
+let kExprI32SExtendI8 = 0xc0;
+let kExprI32SExtendI16 = 0xc1;
+let kExprI64SExtendI8 = 0xc2;
+let kExprI64SExtendI16 = 0xc3;
+let kExprI64SExtendI32 = 0xc4;
+let kExprRefNull = 0xd0;
+let kExprRefIsNull = 0xd1;
+let kExprRefFunc = 0xd2;
+
+// Prefix opcodes
+let kNumericPrefix = 0xfc;
+let kSimdPrefix = 0xfd;
+let kAtomicPrefix = 0xfe;
+
+// Numeric opcodes.
+let kExprMemoryInit = 0x08;
+let kExprDataDrop = 0x09;
+let kExprMemoryCopy = 0x0a;
+let kExprMemoryFill = 0x0b;
+let kExprTableInit = 0x0c;
+let kExprElemDrop = 0x0d;
+let kExprTableCopy = 0x0e;
+let kExprTableGrow = 0x0f;
+let kExprTableSize = 0x10;
+let kExprTableFill = 0x11;
+
+// Atomic opcodes.
+let kExprAtomicNotify = 0x00;
+let kExprI32AtomicWait = 0x01;
+let kExprI64AtomicWait = 0x02;
+let kExprI32AtomicLoad = 0x10;
+let kExprI32AtomicLoad8U = 0x12;
+let kExprI32AtomicLoad16U = 0x13;
+let kExprI32AtomicStore = 0x17;
+let kExprI32AtomicStore8U = 0x19;
+let kExprI32AtomicStore16U = 0x1a;
+let kExprI32AtomicAdd = 0x1e;
+let kExprI32AtomicAdd8U = 0x20;
+let kExprI32AtomicAdd16U = 0x21;
+let kExprI32AtomicSub = 0x25;
+let kExprI32AtomicSub8U = 0x27;
+let kExprI32AtomicSub16U = 0x28;
+let kExprI32AtomicAnd = 0x2c;
+let kExprI32AtomicAnd8U = 0x2e;
+let kExprI32AtomicAnd16U = 0x2f;
+let kExprI32AtomicOr = 0x33;
+let kExprI32AtomicOr8U = 0x35;
+let kExprI32AtomicOr16U = 0x36;
+let kExprI32AtomicXor = 0x3a;
+let kExprI32AtomicXor8U = 0x3c;
+let kExprI32AtomicXor16U = 0x3d;
+let kExprI32AtomicExchange = 0x41;
+let kExprI32AtomicExchange8U = 0x43;
+let kExprI32AtomicExchange16U = 0x44;
+let kExprI32AtomicCompareExchange = 0x48;
+let kExprI32AtomicCompareExchange8U = 0x4a;
+let kExprI32AtomicCompareExchange16U = 0x4b;
+
+let kExprI64AtomicLoad = 0x11;
+let kExprI64AtomicLoad8U = 0x14;
+let kExprI64AtomicLoad16U = 0x15;
+let kExprI64AtomicLoad32U = 0x16;
+let kExprI64AtomicStore = 0x18;
+let kExprI64AtomicStore8U = 0x1b;
+let kExprI64AtomicStore16U = 0x1c;
+let kExprI64AtomicStore32U = 0x1d;
+let kExprI64AtomicAdd = 0x1f;
+let kExprI64AtomicAdd8U = 0x22;
+let kExprI64AtomicAdd16U = 0x23;
+let kExprI64AtomicAdd32U = 0x24;
+let kExprI64AtomicSub = 0x26;
+let kExprI64AtomicSub8U = 0x29;
+let kExprI64AtomicSub16U = 0x2a;
+let kExprI64AtomicSub32U = 0x2b;
+let kExprI64AtomicAnd = 0x2d;
+let kExprI64AtomicAnd8U = 0x30;
+let kExprI64AtomicAnd16U = 0x31;
+let kExprI64AtomicAnd32U = 0x32;
+let kExprI64AtomicOr = 0x34;
+let kExprI64AtomicOr8U = 0x37;
+let kExprI64AtomicOr16U = 0x38;
+let kExprI64AtomicOr32U = 0x39;
+let kExprI64AtomicXor = 0x3b;
+let kExprI64AtomicXor8U = 0x3e;
+let kExprI64AtomicXor16U = 0x3f;
+let kExprI64AtomicXor32U = 0x40;
+let kExprI64AtomicExchange = 0x42;
+let kExprI64AtomicExchange8U = 0x45;
+let kExprI64AtomicExchange16U = 0x46;
+let kExprI64AtomicExchange32U = 0x47;
+let kExprI64AtomicCompareExchange = 0x49
+let kExprI64AtomicCompareExchange8U = 0x4c;
+let kExprI64AtomicCompareExchange16U = 0x4d;
+let kExprI64AtomicCompareExchange32U = 0x4e;
+
+// Simd opcodes.
+let kExprS128LoadMem = 0x00;
+let kExprS128StoreMem = 0x01;
+let kExprI32x4Splat = 0x0c;
+let kExprI32x4Eq = 0x2c;
+let kExprS1x4AllTrue = 0x75;
+let kExprF32x4Min = 0x9e;
 
 class Binary {
   constructor() {
@@ -346,7 +488,7 @@ class Binary {
   }
 
   trunc_buffer() {
-    return this.buffer = this.buffer.slice(0, this.length);
+    return new Uint8Array(this.buffer.buffer, 0, this.length);
   }
 
   reset() {
@@ -372,7 +514,7 @@ class Binary {
     this.buffer[this.length++] = val >> 24;
   }
 
-  emit_leb(val, max_len) {
+  emit_leb_u(val, max_len) {
     this.ensure_space(max_len);
     for (let i = 0; i < max_len; ++i) {
       let v = val & 0xff;
@@ -387,11 +529,11 @@ class Binary {
   }
 
   emit_u32v(val) {
-    this.emit_leb(val, kMaxVarInt32Size);
+    this.emit_leb_u(val, kMaxVarInt32Size);
   }
 
   emit_u64v(val) {
-    this.emit_leb(val, kMaxVarInt64Size);
+    this.emit_leb_u(val, kMaxVarInt64Size);
   }
 
   emit_bytes(data) {
@@ -443,6 +585,16 @@ class WasmFunctionBuilder {
     this.name = name;
     this.type_index = type_index;
     this.body = [];
+    this.locals = [];
+    this.local_names = [];
+  }
+
+  numLocalNames() {
+    let num_local_names = 0;
+    for (let loc_name of this.local_names) {
+      if (loc_name !== undefined) ++num_local_names;
+    }
+    return num_local_names;
   }
 
   exportAs(name) {
@@ -456,9 +608,14 @@ class WasmFunctionBuilder {
   }
 
   addBody(body) {
-    const bodyCopy = body.slice();
-    bodyCopy.push(kExprEnd);
-    return this.addBodyWithEnd(bodyCopy);
+    for (let b of body) {
+      if (typeof b !== 'number' || (b & (~0xFF)) !== 0 )
+        throw new Error('invalid body (entries must be 8 bit numbers): ' + body);
+    }
+    this.body = body.slice();
+    // Automatically add the end for the function block to the body.
+    this.body.push(kExprEnd);
+    return this;
   }
 
   addBodyWithEnd(body) {
@@ -466,8 +623,23 @@ class WasmFunctionBuilder {
     return this;
   }
 
-  addLocals(locals) {
-    this.locals = locals;
+  getNumLocals() {
+    let total_locals = 0;
+    for (let l of this.locals) {
+      for (let type of ["i32", "i64", "f32", "f64", "s128"]) {
+        total_locals += l[type + "_count"] || 0;
+      }
+    }
+    return total_locals;
+  }
+
+  addLocals(locals, names) {
+    const old_num_locals = this.getNumLocals();
+    this.locals.push(locals);
+    if (names) {
+      const missing_names = old_num_locals - this.local_names.length;
+      this.local_names.push(...new Array(missing_names), ...names);
+    }
     return this;
   }
 
@@ -491,21 +663,38 @@ class WasmGlobalBuilder {
   }
 }
 
+class WasmTableBuilder {
+  constructor(module, type, initial_size, max_size) {
+    this.module = module;
+    this.type = type;
+    this.initial_size = initial_size;
+    this.has_max = max_size != undefined;
+    this.max_size = max_size;
+  }
+
+  exportAs(name) {
+    this.module.exports.push({name: name, kind: kExternalTable,
+                              index: this.index});
+    return this;
+  }
+}
+
 class WasmModuleBuilder {
   constructor() {
     this.types = [];
     this.imports = [];
     this.exports = [];
     this.globals = [];
+    this.tables = [];
+    this.exceptions = [];
     this.functions = [];
-    this.table_length_min = 0;
-    this.table_length_max = undefined;
     this.element_segments = [];
     this.data_segments = [];
-    this.segments = [];
     this.explicit = [];
     this.num_imported_funcs = 0;
     this.num_imported_globals = 0;
+    this.num_imported_tables = 0;
+    this.num_imported_exceptions = 0;
     return this;
   }
 
@@ -514,8 +703,8 @@ class WasmModuleBuilder {
     return this;
   }
 
-  addMemory(min, max, exp) {
-    this.memory = {min: min, max: max, exp: exp};
+  addMemory(min, max, exp, shared) {
+    this.memory = {min: min, max: max, exp: exp, shared: shared};
     return this;
   }
 
@@ -524,6 +713,26 @@ class WasmModuleBuilder {
     return this;
   }
 
+  stringToBytes(name) {
+    var result = new Binary();
+    result.emit_string(name);
+    return result.trunc_buffer()
+  }
+
+  createCustomSection(name, bytes) {
+    name = this.stringToBytes(name);
+    var section = new Binary();
+    section.emit_u8(kUnknownSectionCode);
+    section.emit_u32v(name.length + bytes.length);
+    section.emit_bytes(name);
+    section.emit_bytes(bytes);
+    return section.trunc_buffer();
+  }
+
+  addCustomSection(name, bytes) {
+    this.explicit.push(this.createCustomSection(name, bytes));
+  }
+
   addType(type) {
     this.types.push(type);
     var pl = type.params.length;  // should have params
@@ -538,6 +747,24 @@ class WasmModuleBuilder {
     return glob;
   }
 
+  addTable(type, initial_size, max_size = undefined) {
+    if (type != kWasmAnyRef && type != kWasmAnyFunc && type != kWasmExnRef) {
+      throw new Error(
+          'Tables must be of type kWasmAnyRef, kWasmAnyFunc, or kWasmExnRef');
+    }
+    let table = new WasmTableBuilder(this, type, initial_size, max_size);
+    table.index = this.tables.length + this.num_imported_tables;
+    this.tables.push(table);
+    return table;
+  }
+
+  addException(type) {
+    let type_index = (typeof type) == "number" ? type : this.addType(type);
+    let except_index = this.exceptions.length + this.num_imported_exceptions;
+    this.exceptions.push(type_index);
+    return except_index;
+  }
+
   addFunction(name, type) {
     let type_index = (typeof type) == "number" ? type : this.addType(type);
     let func = new WasmFunctionBuilder(this, name, type_index);
@@ -547,6 +774,9 @@ class WasmModuleBuilder {
   }
 
   addImport(module, name, type) {
+    if (this.functions.length != 0) {
+      throw new Error('Imported functions must be declared before local ones');
+    }
     let type_index = (typeof type) == "number" ? type : this.addType(type);
     this.imports.push({module: module, name: name, kind: kExternalFunction,
                        type: type_index});
@@ -554,23 +784,40 @@ class WasmModuleBuilder {
   }
 
   addImportedGlobal(module, name, type, mutable = false) {
+    if (this.globals.length != 0) {
+      throw new Error('Imported globals must be declared before local ones');
+    }
     let o = {module: module, name: name, kind: kExternalGlobal, type: type,
              mutable: mutable};
     this.imports.push(o);
     return this.num_imported_globals++;
   }
 
-  addImportedMemory(module, name, initial = 0, maximum) {
+  addImportedMemory(module, name, initial = 0, maximum, shared) {
     let o = {module: module, name: name, kind: kExternalMemory,
-             initial: initial, maximum: maximum};
+             initial: initial, maximum: maximum, shared: shared};
     this.imports.push(o);
     return this;
   }
 
-  addImportedTable(module, name, initial, maximum) {
+  addImportedTable(module, name, initial, maximum, type) {
+    if (this.tables.length != 0) {
+      throw new Error('Imported tables must be declared before local ones');
+    }
     let o = {module: module, name: name, kind: kExternalTable, initial: initial,
-             maximum: maximum};
+             maximum: maximum, type: type || kWasmAnyFunctionTypeForm};
     this.imports.push(o);
+    return this.num_imported_tables++;
+  }
+
+  addImportedException(module, name, type) {
+    if (this.exceptions.length != 0) {
+      throw new Error('Imported exceptions must be declared before local ones');
+    }
+    let type_index = (typeof type) == "number" ? type : this.addType(type);
+    let o = {module: module, name: name, kind: kExternalException, type: type_index};
+    this.imports.push(o);
+    return this.num_imported_exceptions++;
   }
 
   addExport(name, index) {
@@ -585,7 +832,12 @@ class WasmModuleBuilder {
 
   addDataSegment(addr, data, is_global = false) {
     this.data_segments.push(
-        {addr: addr, data: data, is_global: is_global});
+        {addr: addr, data: data, is_global: is_global, is_active: true});
+    return this.data_segments.length - 1;
+  }
+
+  addPassiveDataSegment(data) {
+    this.data_segments.push({data: data, is_active: false});
     return this.data_segments.length - 1;
   }
 
@@ -593,18 +845,14 @@ class WasmModuleBuilder {
     this.exports.push({name: name, kind: kExternalMemory, index: 0});
   }
 
-  addElementSegment(base, is_global, array, is_import = false) {
-    this.element_segments.push({base: base, is_global: is_global,
-                                    array: array});
-    if (!is_global) {
-      var length = base + array.length;
-      if (length > this.table_length_min && !is_import) {
-        this.table_length_min = length;
-      }
-      if (length > this.table_length_max && !is_import) {
-         this.table_length_max = length;
-      }
-    }
+  addElementSegment(table, base, is_global, array) {
+    this.element_segments.push({table: table, base: base, is_global: is_global,
+                                    array: array, is_active: true});
+    return this;
+  }
+
+  addPassiveElementSegment(array, is_import = false) {
+    this.element_segments.push({array: array, is_active: false});
     return this;
   }
 
@@ -613,12 +861,30 @@ class WasmModuleBuilder {
       if (typeof n != 'number')
         throw new Error('invalid table (entries have to be numbers): ' + array);
     }
-    return this.addElementSegment(this.table_length_min, false, array);
+    if (this.tables.length == 0) {
+      this.addTable(kWasmAnyFunc, 0);
+    }
+    // Adjust the table to the correct size.
+    let table = this.tables[0];
+    const base = table.initial_size;
+    const table_size = base + array.length;
+    table.initial_size = table_size;
+    if (table.has_max && table_size > table.max_size) {
+      table.max_size = table_size;
+    }
+    return this.addElementSegment(0, base, false, array);
   }
 
   setTableBounds(min, max = undefined) {
-    this.table_length_min = min;
-    this.table_length_max = max;
+    if (this.tables.length != 0) {
+      throw new Error("The table bounds of table '0' have already been set.");
+    }
+    this.addTable(kWasmAnyFunc, min, max);
+    return this;
+  }
+
+  setName(name) {
+    this.name = name;
     return this;
   }
 
@@ -664,15 +930,23 @@ class WasmModuleBuilder {
             section.emit_u8(imp.mutable);
           } else if (imp.kind == kExternalMemory) {
             var has_max = (typeof imp.maximum) != "undefined";
-            section.emit_u8(has_max ? 1 : 0); // flags
+            var is_shared = (typeof imp.shared) != "undefined";
+            if (is_shared) {
+              section.emit_u8(has_max ? 3 : 2); // flags
+            } else {
+              section.emit_u8(has_max ? 1 : 0); // flags
+            }
             section.emit_u32v(imp.initial); // initial
             if (has_max) section.emit_u32v(imp.maximum); // maximum
           } else if (imp.kind == kExternalTable) {
-            section.emit_u8(kWasmAnyFunctionTypeForm);
+            section.emit_u8(imp.type);
             var has_max = (typeof imp.maximum) != "undefined";
             section.emit_u8(has_max ? 1 : 0); // flags
             section.emit_u32v(imp.initial); // initial
             if (has_max) section.emit_u32v(imp.maximum); // maximum
+          } else if (imp.kind == kExternalException) {
+            section.emit_u32v(kExceptionAttribute);
+            section.emit_u32v(imp.type);
           } else {
             throw new Error("unknown/unsupported import kind " + imp.kind);
           }
@@ -681,31 +955,27 @@ class WasmModuleBuilder {
     }
 
     // Add functions declarations
-    let has_names = false;
-    let names = false;
     if (wasm.functions.length > 0) {
       if (debug) print("emitting function decls @ " + binary.length);
       binary.emit_section(kFunctionSectionCode, section => {
         section.emit_u32v(wasm.functions.length);
         for (let func of wasm.functions) {
-          has_names = has_names || (func.name != undefined &&
-                                   func.name.length > 0);
           section.emit_u32v(func.type_index);
         }
       });
     }
 
     // Add table section
-    if (wasm.table_length_min > 0) {
-      if (debug) print("emitting table @ " + binary.length);
+    if (wasm.tables.length > 0) {
+      if (debug) print ("emitting tables @ " + binary.length);
       binary.emit_section(kTableSectionCode, section => {
-        section.emit_u8(1);  // one table entry
-        section.emit_u8(kWasmAnyFunctionTypeForm);
-        const max = wasm.table_length_max;
-        const has_max = max !== undefined;
-        section.emit_u8(has_max ? kHasMaximumFlag : 0);
-        section.emit_u32v(wasm.table_length_min);
-        if (has_max) section.emit_u32v(max);
+        section.emit_u32v(wasm.tables.length);
+        for (let table of wasm.tables) {
+          section.emit_u8(table.type);
+          section.emit_u8(table.has_max);
+          section.emit_u32v(table.initial_size);
+          if (table.has_max) section.emit_u32v(table.max_size);
+        }
       });
     }
 
@@ -715,7 +985,13 @@ class WasmModuleBuilder {
       binary.emit_section(kMemorySectionCode, section => {
         section.emit_u8(1);  // one memory entry
         const has_max = wasm.memory.max !== undefined;
-        section.emit_u8(has_max ? 1 : 0);
+        const is_shared = wasm.memory.shared !== undefined;
+        // Emit flags (bit 0: reszeable max, bit 1: shared memory)
+        if (is_shared) {
+          section.emit_u8(has_max ? kSharedHasMaximumFlag : 2);
+        } else {
+          section.emit_u8(has_max ? kHasMaximumFlag : 0);
+        }
         section.emit_u32v(wasm.memory.min);
         if (has_max) section.emit_u32v(wasm.memory.max);
       });
@@ -738,7 +1014,7 @@ class WasmModuleBuilder {
               break;
             case kWasmI64:
               section.emit_u8(kExprI64Const);
-              section.emit_u8(global.init);
+              section.emit_u64v(global.init);
               break;
             case kWasmF32:
               section.emit_u8(kExprF32Const);
@@ -750,10 +1026,22 @@ class WasmModuleBuilder {
               f64_view[0] = global.init;
               section.emit_bytes(f64_bytes_view);
               break;
+            case kWasmAnyFunc:
+            case kWasmAnyRef:
+              if (global.function_index !== undefined) {
+                section.emit_u8(kExprRefFunc);
+                section.emit_u32v(global.function_index);
+              } else {
+                section.emit_u8(kExprRefNull);
+              }
+              break;
+            case kWasmExnRef:
+              section.emit_u8(kExprRefNull);
+              break;
             }
           } else {
             // Emit a global-index initializer.
-            section.emit_u8(kExprGetGlobal);
+            section.emit_u8(kExprGlobalGet);
             section.emit_u32v(global.init_index);
           }
           section.emit_u8(kExprEnd);  // end of init expression
@@ -761,6 +1049,18 @@ class WasmModuleBuilder {
       });
     }
 
+    // Add exceptions.
+    if (wasm.exceptions.length > 0) {
+      if (debug) print("emitting exceptions @ " + binary.length);
+      binary.emit_section(kExceptionSectionCode, section => {
+        section.emit_u32v(wasm.exceptions.length);
+        for (let type of wasm.exceptions) {
+          section.emit_u32v(kExceptionAttribute);
+          section.emit_u32v(type);
+        }
+      });
+    }
+
     // Add export table.
     var mem_export = (wasm.memory !== undefined && wasm.memory.exp);
     var exports_count = wasm.exports.length + (mem_export ? 1 : 0);
@@ -797,22 +1097,55 @@ class WasmModuleBuilder {
         section.emit_u32v(inits.length);
 
         for (let init of inits) {
-          section.emit_u8(0);  // table index / flags
-          if (init.is_global) {
-            section.emit_u8(kExprGetGlobal);
+          if (init.is_active) {
+            // Active segment.
+            if (init.table == 0) {
+              section.emit_u32v(kActiveNoIndex);
+            } else {
+              section.emit_u32v(kActiveWithIndex);
+              section.emit_u32v(init.table);
+            }
+            if (init.is_global) {
+              section.emit_u8(kExprGlobalGet);
+            } else {
+              section.emit_u8(kExprI32Const);
+            }
+            section.emit_u32v(init.base);
+            section.emit_u8(kExprEnd);
+            if (init.table != 0) {
+              section.emit_u8(kExternalFunction);
+            }
+            section.emit_u32v(init.array.length);
+            for (let index of init.array) {
+              section.emit_u32v(index);
+            }
           } else {
-            section.emit_u8(kExprI32Const);
-          }
-          section.emit_u32v(init.base);
-          section.emit_u8(kExprEnd);
-          section.emit_u32v(init.array.length);
-          for (let index of init.array) {
-            section.emit_u32v(index);
+            // Passive segment.
+            section.emit_u8(kPassiveWithElements);  // flags
+            section.emit_u8(kWasmAnyFunc);
+            section.emit_u32v(init.array.length);
+            for (let index of init.array) {
+              if (index === null) {
+                section.emit_u8(kExprRefNull);
+                section.emit_u8(kExprEnd);
+              } else {
+                section.emit_u8(kExprRefFunc);
+                section.emit_u32v(index);
+                section.emit_u8(kExprEnd);
+              }
+            }
           }
         }
       });
     }
 
+    // If there are any passive data segments, add the DataCount section.
+    if (wasm.data_segments.some(seg => !seg.is_active)) {
+      binary.emit_section(kDataCountSectionCode, section => {
+        section.emit_u32v(wasm.data_segments.length);
+      });
+    }
+
     // Add function bodies.
     if (wasm.functions.length > 0) {
       // emit function bodies
@@ -824,9 +1157,7 @@ class WasmModuleBuilder {
           header.reset();
           // Function body length will be patched later.
           let local_decls = [];
-          let l = func.locals;
-          if (l != undefined) {
-            let local_decls_count = 0;
+          for (let l of func.locals || []) {
             if (l.i32_count > 0) {
               local_decls.push({count: l.i32_count, type: kWasmI32});
             }
@@ -839,6 +1170,18 @@ class WasmModuleBuilder {
             if (l.f64_count > 0) {
               local_decls.push({count: l.f64_count, type: kWasmF64});
             }
+            if (l.s128_count > 0) {
+              local_decls.push({count: l.s128_count, type: kWasmS128});
+            }
+            if (l.anyref_count > 0) {
+              local_decls.push({count: l.anyref_count, type: kWasmAnyRef});
+            }
+            if (l.anyfunc_count > 0) {
+              local_decls.push({count: l.anyfunc_count, type: kWasmAnyFunc});
+            }
+            if (l.except_count > 0) {
+              local_decls.push({count: l.except_count, type: kWasmExnRef});
+            }
           }
 
           header.emit_u32v(local_decls.length);
@@ -860,17 +1203,21 @@ class WasmModuleBuilder {
       binary.emit_section(kDataSectionCode, section => {
         section.emit_u32v(wasm.data_segments.length);
         for (let seg of wasm.data_segments) {
-          section.emit_u8(0);  // linear memory index 0 / flags
-          if (seg.is_global) {
-            // initializer is a global variable
-            section.emit_u8(kExprGetGlobal);
-            section.emit_u32v(seg.addr);
+          if (seg.is_active) {
+            section.emit_u8(0);  // linear memory index 0 / flags
+            if (seg.is_global) {
+              // initializer is a global variable
+              section.emit_u8(kExprGlobalGet);
+              section.emit_u32v(seg.addr);
+            } else {
+              // initializer is a constant
+              section.emit_u8(kExprI32Const);
+              section.emit_u32v(seg.addr);
+            }
+            section.emit_u8(kExprEnd);
           } else {
-            // initializer is a constant
-            section.emit_u8(kExprI32Const);
-            section.emit_u32v(seg.addr);
+            section.emit_u8(kPassive);  // flags
           }
-          section.emit_u8(kExprEnd);
           section.emit_u32v(seg.data.length);
           section.emit_bytes(seg.data);
         }
@@ -883,21 +1230,50 @@ class WasmModuleBuilder {
       binary.emit_bytes(exp);
     }
 
-    // Add function names.
-    if (has_names) {
-      if (debug) print("emitting names @ " + binary.length);
+    // Add names.
+    let num_function_names = 0;
+    let num_functions_with_local_names = 0;
+    for (let func of wasm.functions) {
+      if (func.name !== undefined) ++num_function_names;
+      if (func.numLocalNames() > 0) ++num_functions_with_local_names;
+    }
+    if (num_function_names > 0 || num_functions_with_local_names > 0 ||
+        wasm.name !== undefined) {
+      if (debug) print('emitting names @ ' + binary.length);
       binary.emit_section(kUnknownSectionCode, section => {
-        section.emit_string("name");
-        var count = wasm.functions.length + wasm.num_imported_funcs;
-        section.emit_u32v(count);
-        for (var i = 0; i < wasm.num_imported_funcs; i++) {
-          section.emit_u8(0); // empty string
-          section.emit_u8(0); // local names count == 0
+        section.emit_string('name');
+        // Emit module name.
+        if (wasm.name !== undefined) {
+          section.emit_section(kModuleNameCode, name_section => {
+            name_section.emit_string(wasm.name);
+          });
         }
-        for (let func of wasm.functions) {
-          var name = func.name == undefined ? "" : func.name;
-          section.emit_string(name);
-          section.emit_u8(0);  // local names count == 0
+        // Emit function names.
+        if (num_function_names > 0) {
+          section.emit_section(kFunctionNamesCode, name_section => {
+            name_section.emit_u32v(num_function_names);
+            for (let func of wasm.functions) {
+              if (func.name === undefined) continue;
+              name_section.emit_u32v(func.index);
+              name_section.emit_string(func.name);
+            }
+          });
+        }
+        // Emit local names.
+        if (num_functions_with_local_names > 0) {
+          section.emit_section(kLocalNamesCode, name_section => {
+            name_section.emit_u32v(num_functions_with_local_names);
+            for (let func of wasm.functions) {
+              if (func.numLocalNames() == 0) continue;
+              name_section.emit_u32v(func.index);
+              name_section.emit_u32v(func.numLocalNames());
+              for (let i = 0; i < func.local_names.length; ++i) {
+                if (func.local_names[i] === undefined) continue;
+                name_section.emit_u32v(i);
+                name_section.emit_string(func.local_names[i]);
+              }
+            }
+          });
         }
       });
     }
@@ -925,13 +1301,24 @@ class WasmModuleBuilder {
   }
 }
 
-function wasmI32Const(val) {
-  let bytes = [kExprI32Const];
-  for (let i = 0; i < 4; ++i) {
-    bytes.push(0x80 | ((val >> (7 * i)) & 0x7f));
+function wasmSignedLeb(val, max_len = 5) {
+  let res = [];
+  for (let i = 0; i < max_len; ++i) {
+    let v = val & 0x7f;
+    // If {v} sign-extended from 7 to 32 bits is equal to val, we are done.
+    if (((v << 25) >> 25) == val) {
+      res.push(v);
+      return res;
+    }
+    res.push(v | 0x80);
+    val = val >> 7;
   }
-  bytes.push((val >> (7 * 4)) & 0x7f);
-  return bytes;
+  throw new Error(
+      'Leb value <' + val + '> exceeds maximum length of ' + max_len);
+}
+
+function wasmI32Const(val) {
+  return [kExprI32Const, ...wasmSignedLeb(val, 5)];
 }
 
 function wasmF32Const(f) {