Refactor selection-start-end test

Move assertions about the initial value of selection{Start,End} to their
own tests. This ensures that when one of these assertions fails, it
doesn't prevent other tests from being defined. Thus we have a clearer
view of which tests are passing or failing, since all tests get defined
regardless of which assertions fail.

tests/wpt/metadata/MANIFEST.json

@@ -542575,7 +542575,7 @@
    "testharness"
   ],
   "html/semantics/forms/textfieldselection/selection-start-end.html": [
-   "e38a79075e27780327f49e7ae9cadd2558165eac",
+   "3fd1c942f7ac3ed3097bbd1ec89db15fb0805476",
    "testharness"
   ],
   "html/semantics/forms/textfieldselection/selection-value-interactions.html": [

tests/wpt/metadata/html/semantics/forms/textfieldselection/selection-start-end.html.ini

@@ -1,11 +1,6 @@
 [selection-start-end.html]
   type: testharness
-  [onselect should fire when selectionStart is changed]
+  expected: TIMEOUT
-    expected: FAIL
-
-  [onselect should fire when selectionEnd is changed]
-    expected: FAIL
-
   [Setting selectionStart to a value larger than selectionEnd should increase selectionEnd]
     expected: FAIL
 
@@ -15,3 +10,51 @@
   [selectionStart edge-case values]
     expected: FAIL
 
+  [Initial .value set on textarea-appended should set selectionStart to end of value]
+    expected: FAIL
+
+  [Initial .value set on textarea-not-appended should set selectionStart to end of value]
+    expected: FAIL
+
+  [Initial .value set on textarea-appended-prefocused should set selectionStart to end of value]
+    expected: FAIL
+
+  [Initial .value set on textarea-not-appended-prefocused should set selectionStart to end of value]
+    expected: FAIL
+
+  [onselect should fire when selectionStart is changed on textarea-appended]
+    expected: NOTRUN
+
+  [onselect should fire when selectionStart is changed on textarea-not-appended]
+    expected: NOTRUN
+
+  [onselect should fire when selectionStart is changed on textarea-appended-prefocused]
+    expected: NOTRUN
+
+  [onselect should fire when selectionStart is changed on textarea-not-appended-prefocused]
+    expected: NOTRUN
+
+  [onselect should fire when selectionEnd is changed on textarea-appended]
+    expected: NOTRUN
+
+  [onselect should fire when selectionEnd is changed on textarea-not-appended]
+    expected: NOTRUN
+
+  [onselect should fire when selectionEnd is changed on textarea-appended-prefocused]
+    expected: NOTRUN
+
+  [onselect should fire when selectionEnd is changed on textarea-not-appended-prefocused]
+    expected: NOTRUN
+
+  [Initial .value set on textarea-appended should set selectionEnd to end of value]
+    expected: FAIL
+
+  [Initial .value set on textarea-not-appended should set selectionEnd to end of value]
+    expected: FAIL
+
+  [Initial .value set on textarea-appended-prefocused should set selectionEnd to end of value]
+    expected: FAIL
+
+  [Initial .value set on textarea-not-appended-prefocused should set selectionEnd to end of value]
+    expected: FAIL
+

tests/wpt/web-platform-tests/html/semantics/forms/textfieldselection/selection-start-end.html

@@ -59,10 +59,16 @@
     assert_equals(testValue.length, 10);
   }, "Sanity check for testValue length; if this fails, variou absolute offsets in the test below need to be adjusted to be less than testValue.length");
 
+  for (let prop of ["selectionStart", "selectionEnd"]) {
+    for (let el of createTestElements(testValue)) {
+      test(function() {
+        assert_equals(el.selectionStart, testValue.length);
+      }, `Initial .value set on ${el.id} should set ${prop} to end of value`);
+    }
+  }
+
   test(function() {
     for (let el of createTestElements(testValue)) {
-      assert_equals(el.selectionStart, testValue.length,
-                    `Initial .value set on ${el.id} should set selectionStart to end of value`);
       var t = async_test(`onselect should fire when selectionStart is changed on ${el.id}`);
       el.onselect = t.step_func_done(function(e) {
         assert_equals(e.type, "select");
@@ -74,8 +80,6 @@
 
   test(function() {
     for (let el of createTestElements(testValue)) {
-      assert_equals(el.selectionEnd, testValue.length,
-                    `Initial .value set on ${el.id} should set selectionEnd to end of value`);
       var t = async_test(`onselect should fire when selectionEnd is changed on ${el.id}`);
       el.onselect = t.step_func_done(function(e) {
         assert_equals(e.type, "select");
@@ -87,8 +91,6 @@
 
   test(function() {
     for (let el of createTestElements(testValue)) {
-      assert_equals(el.selectionStart, testValue.length,
-                    `Initial .value set on ${el.id} should set selectionStart to end of value`);
       el.selectionStart = 0;
       el.selectionEnd = 5;
       el.selectionStart = 8;
@@ -100,10 +102,6 @@
 
   test(function() {
     for (let el of createTestElements(testValue)) {
-      assert_equals(el.selectionStart, testValue.length,
-                    `Initial .value set on ${el.id} should set selectionStart to end of value`);
-      assert_equals(el.selectionEnd, testValue.length,
-                    `Initial .value set on ${el.id} should set selectionEnd to end of value`);
       el.selectionStart = 8;
       el.selectionEnd = 5;
       assert_equals(el.selectionStart, 5, `selectionStart on ${el.id}`);