diff --git a/tests/wpt/include.ini b/tests/wpt/include.ini
index fb3e67eab21..11f15fd79f0 100644
--- a/tests/wpt/include.ini
+++ b/tests/wpt/include.ini
@@ -49,6 +49,8 @@ skip: true
     skip: true
   [css-inline]
     skip: true
+    [baseline-source]
+      skip: false
   [css-layout-api]
     skip: true
   [css-masking]
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-computed.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-computed.html.ini
new file mode 100644
index 00000000000..6c85167ba57
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-computed.html.ini
@@ -0,0 +1,9 @@
+[baseline-source-computed.html]
+  [Property baseline-source value 'auto']
+    expected: FAIL
+
+  [Property baseline-source value 'first']
+    expected: FAIL
+
+  [Property baseline-source value 'last']
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-001.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-001.html.ini
new file mode 100644
index 00000000000..37de04db8b8
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-001.html.ini
@@ -0,0 +1,42 @@
+[baseline-source-first-001.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 14]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-002.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-002.html.ini
new file mode 100644
index 00000000000..e40b09309a7
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-002.html.ini
@@ -0,0 +1,60 @@
+[baseline-source-first-002.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 16]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
+
+  [.target > * 22]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-003.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-003.html.ini
new file mode 100644
index 00000000000..32dffb1fe66
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-003.html.ini
@@ -0,0 +1,60 @@
+[baseline-source-first-003.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 16]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
+
+  [.target > * 22]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-textarea-001.tentative.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-textarea-001.tentative.html.ini
new file mode 100644
index 00000000000..431bd9eae41
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-textarea-001.tentative.html.ini
@@ -0,0 +1,18 @@
+[baseline-source-first-textarea-001.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-textarea-002.tentative.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-textarea-002.tentative.html.ini
new file mode 100644
index 00000000000..dc0c464b303
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-textarea-002.tentative.html.ini
@@ -0,0 +1,36 @@
+[baseline-source-first-textarea-002.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-textarea-003.tentative.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-textarea-003.tentative.html.ini
new file mode 100644
index 00000000000..ccbf7ec71c3
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-first-textarea-003.tentative.html.ini
@@ -0,0 +1,36 @@
+[baseline-source-first-textarea-003.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-001.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-001.html.ini
new file mode 100644
index 00000000000..1842ec43d8a
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-001.html.ini
@@ -0,0 +1,33 @@
+[baseline-source-last-001.html]
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 14]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-002.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-002.html.ini
new file mode 100644
index 00000000000..a68ef63d891
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-002.html.ini
@@ -0,0 +1,60 @@
+[baseline-source-last-002.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 16]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
+
+  [.target > * 22]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-003.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-003.html.ini
new file mode 100644
index 00000000000..c51dd83c432
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-003.html.ini
@@ -0,0 +1,60 @@
+[baseline-source-last-003.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 16]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
+
+  [.target > * 22]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-textarea-001.tentative.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-textarea-001.tentative.html.ini
new file mode 100644
index 00000000000..c5076ec4117
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-textarea-001.tentative.html.ini
@@ -0,0 +1,9 @@
+[baseline-source-last-textarea-001.tentative.html]
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-textarea-002.tentative.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-textarea-002.tentative.html.ini
new file mode 100644
index 00000000000..4f640310374
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-textarea-002.tentative.html.ini
@@ -0,0 +1,36 @@
+[baseline-source-last-textarea-002.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-textarea-003.tentative.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-textarea-003.tentative.html.ini
new file mode 100644
index 00000000000..dd0573ccef5
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-last-textarea-003.tentative.html.ini
@@ -0,0 +1,36 @@
+[baseline-source-last-textarea-003.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-no-interpolation.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-no-interpolation.html.ini
new file mode 100644
index 00000000000..1b550175cb7
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-no-interpolation.html.ini
@@ -0,0 +1,126 @@
+[baseline-source-no-interpolation.html]
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.3) should be [initial\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [initial\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (0) should be [initial\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (0.3) should be [initial\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (0) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (0.3) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (0) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (0.3) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (0) should be [initial\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-valid.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-valid.html.ini
new file mode 100644
index 00000000000..000b6d6c757
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-valid.html.ini
@@ -0,0 +1,9 @@
+[baseline-source-valid.html]
+  [e.style['baseline-source'\] = "auto" should set the property value]
+    expected: FAIL
+
+  [e.style['baseline-source'\] = "first" should set the property value]
+    expected: FAIL
+
+  [e.style['baseline-source'\] = "last" should set the property value]
+    expected: FAIL
diff --git a/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-vertical-align.html.ini b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-vertical-align.html.ini
new file mode 100644
index 00000000000..a5688f5a7bd
--- /dev/null
+++ b/tests/wpt/meta-legacy-layout/css/css-inline/baseline-source/baseline-source-vertical-align.html.ini
@@ -0,0 +1,3 @@
+[baseline-source-vertical-align.html]
+  [baseline-source-vertical-align]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-computed.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-computed.html.ini
new file mode 100644
index 00000000000..6c85167ba57
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-computed.html.ini
@@ -0,0 +1,9 @@
+[baseline-source-computed.html]
+  [Property baseline-source value 'auto']
+    expected: FAIL
+
+  [Property baseline-source value 'first']
+    expected: FAIL
+
+  [Property baseline-source value 'last']
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-001.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-001.html.ini
new file mode 100644
index 00000000000..f2ce445f9dc
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-001.html.ini
@@ -0,0 +1,45 @@
+[baseline-source-first-001.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 14]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-002.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-002.html.ini
new file mode 100644
index 00000000000..da0a1377ccd
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-002.html.ini
@@ -0,0 +1,57 @@
+[baseline-source-first-002.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 16]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
+
+  [.target > * 22]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-003.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-003.html.ini
new file mode 100644
index 00000000000..c37520bede0
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-003.html.ini
@@ -0,0 +1,57 @@
+[baseline-source-first-003.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 16]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
+
+  [.target > * 22]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-textarea-001.tentative.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-textarea-001.tentative.html.ini
new file mode 100644
index 00000000000..431bd9eae41
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-textarea-001.tentative.html.ini
@@ -0,0 +1,18 @@
+[baseline-source-first-textarea-001.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-textarea-002.tentative.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-textarea-002.tentative.html.ini
new file mode 100644
index 00000000000..dc0c464b303
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-textarea-002.tentative.html.ini
@@ -0,0 +1,36 @@
+[baseline-source-first-textarea-002.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-textarea-003.tentative.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-textarea-003.tentative.html.ini
new file mode 100644
index 00000000000..ccbf7ec71c3
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-first-textarea-003.tentative.html.ini
@@ -0,0 +1,36 @@
+[baseline-source-first-textarea-003.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-001.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-001.html.ini
new file mode 100644
index 00000000000..20172a2a57f
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-001.html.ini
@@ -0,0 +1,39 @@
+[baseline-source-last-001.html]
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 14]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-002.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-002.html.ini
new file mode 100644
index 00000000000..96c7c23b0b0
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-002.html.ini
@@ -0,0 +1,57 @@
+[baseline-source-last-002.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 16]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
+
+  [.target > * 22]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-003.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-003.html.ini
new file mode 100644
index 00000000000..003bbaeb17f
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-003.html.ini
@@ -0,0 +1,57 @@
+[baseline-source-last-003.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 13]
+    expected: FAIL
+
+  [.target > * 15]
+    expected: FAIL
+
+  [.target > * 16]
+    expected: FAIL
+
+  [.target > * 17]
+    expected: FAIL
+
+  [.target > * 18]
+    expected: FAIL
+
+  [.target > * 19]
+    expected: FAIL
+
+  [.target > * 20]
+    expected: FAIL
+
+  [.target > * 21]
+    expected: FAIL
+
+  [.target > * 22]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-textarea-001.tentative.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-textarea-001.tentative.html.ini
new file mode 100644
index 00000000000..c5076ec4117
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-textarea-001.tentative.html.ini
@@ -0,0 +1,9 @@
+[baseline-source-last-textarea-001.tentative.html]
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-textarea-002.tentative.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-textarea-002.tentative.html.ini
new file mode 100644
index 00000000000..4f640310374
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-textarea-002.tentative.html.ini
@@ -0,0 +1,36 @@
+[baseline-source-last-textarea-002.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-textarea-003.tentative.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-textarea-003.tentative.html.ini
new file mode 100644
index 00000000000..dd0573ccef5
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-last-textarea-003.tentative.html.ini
@@ -0,0 +1,36 @@
+[baseline-source-last-textarea-003.tentative.html]
+  [.target > * 1]
+    expected: FAIL
+
+  [.target > * 2]
+    expected: FAIL
+
+  [.target > * 3]
+    expected: FAIL
+
+  [.target > * 4]
+    expected: FAIL
+
+  [.target > * 5]
+    expected: FAIL
+
+  [.target > * 6]
+    expected: FAIL
+
+  [.target > * 7]
+    expected: FAIL
+
+  [.target > * 8]
+    expected: FAIL
+
+  [.target > * 9]
+    expected: FAIL
+
+  [.target > * 10]
+    expected: FAIL
+
+  [.target > * 11]
+    expected: FAIL
+
+  [.target > * 12]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-no-interpolation.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-no-interpolation.html.ini
new file mode 100644
index 00000000000..1b550175cb7
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-no-interpolation.html.ini
@@ -0,0 +1,126 @@
+[baseline-source-no-interpolation.html]
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0) should be [initial\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.3) should be [initial\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [initial\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (0) should be [initial\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (0.3) should be [initial\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [Web Animations: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-behavior:allow-discrete: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (0) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (0.3) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (0) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (0.3) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Transitions with transition: all: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (-0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (0) should be [initial\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (0.3) should be [initial\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (0.5) should be [last\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (0.6) should be [last\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (1) should be [last\]]
+    expected: FAIL
+
+  [CSS Animations: property <baseline-source> from [initial\] to [last\] at (1.5) should be [last\]]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-valid.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-valid.html.ini
new file mode 100644
index 00000000000..000b6d6c757
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-valid.html.ini
@@ -0,0 +1,9 @@
+[baseline-source-valid.html]
+  [e.style['baseline-source'\] = "auto" should set the property value]
+    expected: FAIL
+
+  [e.style['baseline-source'\] = "first" should set the property value]
+    expected: FAIL
+
+  [e.style['baseline-source'\] = "last" should set the property value]
+    expected: FAIL
diff --git a/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-vertical-align.html.ini b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-vertical-align.html.ini
new file mode 100644
index 00000000000..a5688f5a7bd
--- /dev/null
+++ b/tests/wpt/meta/css/css-inline/baseline-source/baseline-source-vertical-align.html.ini
@@ -0,0 +1,3 @@
+[baseline-source-vertical-align.html]
+  [baseline-source-vertical-align]
+    expected: FAIL