diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/selectors/parsing/parse-has.txt b/Tests/LibWeb/Text/expected/wpt-import/css/selectors/parsing/parse-has.txt
new file mode 100644
index 00000000000..dbc9fa4fa3f
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/selectors/parsing/parse-has.txt
@@ -0,0 +1,35 @@
+Harness status: OK
+
+Found 29 tests
+
+6 Pass
+23 Fail
+Fail	":has(a)" should be a valid selector
+Fail	":has(#a)" should be a valid selector
+Fail	":has(.a)" should be a valid selector
+Fail	":has([a])" should be a valid selector
+Fail	":has([a=\"b\"])" should be a valid selector
+Fail	":has([a|=\"b\"])" should be a valid selector
+Fail	":has(:hover)" should be a valid selector
+Fail	"*:has(.a)" should be a valid selector
+Fail	".a:has(.b)" should be a valid selector
+Fail	".a:has(> .b)" should be a valid selector
+Fail	".a:has(~ .b)" should be a valid selector
+Fail	".a:has(+ .b)" should be a valid selector
+Fail	".a:has(.b) .c" should be a valid selector
+Fail	".a .b:has(.c)" should be a valid selector
+Fail	".a .b:has(.c .d)" should be a valid selector
+Fail	".a .b:has(.c .d) .e" should be a valid selector
+Fail	".a:has(.b:is(.c .d))" should be a valid selector
+Fail	".a:is(.b:has(.c) .d)" should be a valid selector
+Fail	".a:not(:has(.b))" should be a valid selector
+Fail	".a:has(:not(.b))" should be a valid selector
+Fail	".a:has(.b):has(.c)" should be a valid selector
+Fail	"*|*:has(*)" should be a valid selector
+Fail	":has(*|*)" should be a valid selector
+Pass	":has" should be an invalid selector
+Pass	".a:has" should be an invalid selector
+Pass	".a:has b" should be an invalid selector
+Pass	":has()" should be an invalid selector
+Pass	":has(123)" should be an invalid selector
+Pass	":has(.a, 123)" should be an invalid selector
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/selectors/parsing/parse-is-where.txt b/Tests/LibWeb/Text/expected/wpt-import/css/selectors/parsing/parse-is-where.txt
new file mode 100644
index 00000000000..701125889ec
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/selectors/parsing/parse-is-where.txt
@@ -0,0 +1,39 @@
+Harness status: OK
+
+Found 33 tests
+
+24 Pass
+9 Fail
+Pass	":is(div )" should be a valid selector
+Pass	":where(div )" should be a valid selector
+Pass	":is(div + bar, div ~ .baz)" should be a valid selector
+Pass	":where(div + bar, div ~ .baz)" should be a valid selector
+Pass	":is(:is(div))" should be a valid selector
+Pass	":where(:is(div))" should be a valid selector
+Pass	":is(:where(div))" should be a valid selector
+Pass	":where(:where(div))" should be a valid selector
+Pass	":host(:is(div))" should be a valid selector
+Pass	":host(:where(div))" should be a valid selector
+Pass	":host(:is(div ))" should be a valid selector
+Pass	":host(:where(div ))" should be a valid selector
+Fail	":host(:is(div .foo))" should be a valid selector
+Fail	":host(:where(div .foo))" should be a valid selector
+Pass	":is(:hover, :active)" should be a valid selector
+Pass	":where(:hover, :active)" should be a valid selector
+Pass	":is(div):hover" should be a valid selector
+Pass	":where(div):hover" should be a valid selector
+Pass	":is(div)::before" should be a valid selector
+Pass	":where(div)::before" should be a valid selector
+Fail	":is(::before)" should be a valid selector
+Fail	":where(::before)" should be a valid selector
+Pass	":is(div) + bar" should be a valid selector
+Pass	":where(div) + bar" should be a valid selector
+Fail	"::part(foo):is(:hover)" should be a valid selector
+Fail	"::part(foo):where(:hover)" should be a valid selector
+Fail	"::part(foo):is([attr='value'])" should be a valid selector
+Fail	"::part(foo):where([attr='value'])" should be a valid selector
+Pass	":not(:is(div))" should be a valid selector
+Pass	":not(:where(div))" should be a valid selector
+Pass	":not(:is(div .foo))" should be a valid selector
+Pass	":not(:where(div .foo))" should be a valid selector
+Fail	":is(# C4єанйтж╕/┘ГЁжЮХєа▓┐ЁЭБМєаСеЁЭЖА%=[ямм0)" should be an invalid selector
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/selectors/parsing/parse-not.txt b/Tests/LibWeb/Text/expected/wpt-import/css/selectors/parsing/parse-not.txt
new file mode 100644
index 00000000000..2ad66de966f
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/selectors/parsing/parse-not.txt
@@ -0,0 +1,32 @@
+Harness status: OK
+
+Found 26 tests
+
+23 Pass
+3 Fail
+Pass	"button:not([disabled])" should be a valid selector
+Pass	"*:not(foo)" should be a valid selector
+Pass	":not(:link):not(:visited)" should be a valid selector
+Fail	"*|*:not(*)" should be a valid selector
+Pass	":not(:hover)" should be a valid selector
+Pass	":not(*|*)" should be a valid selector
+Pass	"foo:not(bar)" should be a valid selector
+Pass	":not(:not(foo))" should be a valid selector
+Pass	":not(.a .b)" should be a valid selector
+Pass	":not(.a + .b)" should be a valid selector
+Pass	":not(.a .b ~ c)" should be a valid selector
+Pass	":not(span.a, div.b)" should be a valid selector
+Pass	":not(.a .b ~ c, .d .e)" should be a valid selector
+Pass	":not(:host)" should be a valid selector
+Pass	":not(:host(.a))" should be a valid selector
+Pass	":host(:not(.a))" should be a valid selector
+Pass	":not(:host(:not(.a)))" should be a valid selector
+Pass	":not([disabled][selected])" should be a valid selector
+Pass	":not([disabled],[selected])" should be a valid selector
+Pass	":not()" should be an invalid selector
+Pass	":not(:not())" should be an invalid selector
+Fail	":not(::before)" should be an invalid selector
+Pass	":not(:unknownpseudo)" should be an invalid selector
+Pass	":not(.a, :unknownpseudo)" should be an invalid selector
+Pass	":not(:unknownpseudo, .a)" should be an invalid selector
+Fail	":host(:not(.a .b))" should be an invalid selector
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/selectors/parsing/parse-has.html b/Tests/LibWeb/Text/input/wpt-import/css/selectors/parsing/parse-has.html
new file mode 100644
index 00000000000..68f38953525
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/selectors/parsing/parse-has.html
@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Selectors: The relational pseudo-class</title>
+<link rel="author" title="Byungwoo Lee" href="mailto:blee@igalia.com">
+<link rel="help" href="https://drafts.csswg.org/selectors-4/#has-pseudo">
+<script src="../../../resources/testharness.js"></script>
+<script src="../../../resources/testharnessreport.js"></script>
+<script src="../../../css/support/parsing-testcommon.js"></script>
+<script>
+  test_valid_selector(':has(a)');
+  test_valid_selector(':has(#a)');
+  test_valid_selector(':has(.a)');
+  test_valid_selector(':has([a])');
+  test_valid_selector(':has([a="b"])');
+  test_valid_selector(':has([a|="b"])');
+  test_valid_selector(':has(:hover)');
+  test_valid_selector('*:has(.a)', ['*:has(.a)', ':has(.a)']);
+  test_valid_selector('.a:has(.b)');
+  test_valid_selector('.a:has(> .b)');
+  test_valid_selector('.a:has(~ .b)');
+  test_valid_selector('.a:has(+ .b)');
+  test_valid_selector('.a:has(.b) .c');
+  test_valid_selector('.a .b:has(.c)');
+  test_valid_selector('.a .b:has(.c .d)');
+  test_valid_selector('.a .b:has(.c .d) .e');
+  test_valid_selector('.a:has(.b:is(.c .d))');
+  test_valid_selector('.a:is(.b:has(.c) .d)');
+  test_valid_selector('.a:not(:has(.b))');
+  test_valid_selector('.a:has(:not(.b))');
+  test_valid_selector('.a:has(.b):has(.c)');
+  test_valid_selector('*|*:has(*)', ':has(*)');
+  test_valid_selector(':has(*|*)', ':has(*)');
+  test_invalid_selector(':has');
+  test_invalid_selector('.a:has');
+  test_invalid_selector('.a:has b');
+  /* :has() is unforgiving, but :is() can still forgive */
+  test_invalid_selector(':has()');
+  test_invalid_selector(':has(123)');
+  test_invalid_selector(':has(.a, 123)');
+</script>
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/selectors/parsing/parse-is-where.html b/Tests/LibWeb/Text/input/wpt-import/css/selectors/parsing/parse-is-where.html
new file mode 100644
index 00000000000..04674edb9e4
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/selectors/parsing/parse-is-where.html
@@ -0,0 +1,50 @@
+<!doctype html>
+<title>CSS Selectors: :is() and :where() parsing</title>
+<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
+<link rel="help" href="https://drafts.csswg.org/selectors-4/#matches">
+<link rel="help" href="https://drafts.csswg.org/selectors-4/#zero-matches">
+<script src="../../../resources/testharness.js"></script>
+<script src="../../../resources/testharnessreport.js"></script>
+<script src="../../../css/support/parsing-testcommon.js"></script>
+<script>
+  function assert_valid(valid, pattern, expected_pattern, description) {
+    for (let pseudo of ["is", "where"]) {
+      let selector = pattern.replace("{}", ":" + pseudo);
+      let expected_selector = selector;
+      if (expected_pattern != null)
+        expected_selector = expected_pattern.replace("{}", ":" + pseudo);
+      if (valid) {
+        test_valid_selector(selector, expected_selector);
+      } else {
+        test_valid_forgiving_selector(selector);
+      }
+    }
+  }
+
+  assert_valid(true, "{}(div )", "{}(div)", "Trailing whitespace");
+  assert_valid(true, "{}(div + bar, div ~ .baz)", null, "Multiple selectors with combinators");
+
+  assert_valid(true, "{}(:is(div))", null, "Nested :is");
+  assert_valid(true, "{}(:where(div))", null, "Nested :where");
+
+  assert_valid(true, ":host({}(div))", null, "Nested inside :host, without combinators");
+  assert_valid(true, ":host({}(div ))", ":host({}(div))", "Nested inside :host, with trailing whitespace");
+  // See https://github.com/w3c/csswg-drafts/issues/5093
+  assert_valid(false, ":host({}(div .foo))", null, "Nested inside :host, with combinators");
+
+  assert_valid(true, "{}(:hover, :active)", null, "Pseudo-classes inside");
+  assert_valid(true, "{}(div):hover", null, "Pseudo-classes after");
+  assert_valid(true, "{}(div)::before", null, "Pseudo-elements after");
+  assert_valid(false, "{}(::before)", null, "Pseudo-elements inside");
+
+  assert_valid(true, "{}(div) + bar", null, "Combinators after");
+  assert_valid(true, "::part(foo){}(:hover)", null, "After part with simple pseudo-class");
+  assert_valid(false, "::part(foo){}([attr='value'])", null, "After part with invalid selector after");
+
+  assert_valid(true, ":not({}(div))", null, "Nested inside :not, without combinators");
+  assert_valid(true, ":not({}(div .foo))", null, "Nested inside :not, with combinators");
+  // This should be invalid even with the forgiving behavior because
+  // `<any-value>` doesn't allow bad tokens:
+  // https://drafts.csswg.org/css-syntax-3/#typedef-declaration-value
+  test_invalid_selector(`:is(# C4єанйтж╕/┘ГЁжЮХєа▓┐ЁЭБМєаСеЁЭЖА%=[ямм0)`);
+</script>
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/selectors/parsing/parse-not.html b/Tests/LibWeb/Text/input/wpt-import/css/selectors/parsing/parse-not.html
new file mode 100644
index 00000000000..7c8eef83829
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/selectors/parsing/parse-not.html
@@ -0,0 +1,37 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Selectors: The negation pseudo-class</title>
+<link rel="help" href="https://drafts.csswg.org/selectors-3/#negation">
+<script src="../../../resources/testharness.js"></script>
+<script src="../../../resources/testharnessreport.js"></script>
+<script src="../../../css/support/parsing-testcommon.js"></script>
+<script>
+  test_valid_selector('button:not([disabled])');
+  test_valid_selector('*:not(foo)',
+      ['*:not(foo)', ':not(foo)']);
+  test_valid_selector(':not(:link):not(:visited)');
+  test_valid_selector('*|*:not(*)', ':not(*)');
+  test_valid_selector(':not(:hover)');
+  test_valid_selector(':not(*|*)', ':not(*)');
+  test_valid_selector('foo:not(bar)');
+  test_valid_selector(':not(:not(foo))');
+  test_valid_selector(':not(.a .b)');
+  test_valid_selector(':not(.a + .b)');
+  test_valid_selector(':not(.a .b ~ c)');
+  test_valid_selector(':not(span.a, div.b)');
+  test_valid_selector(':not(.a .b ~ c, .d .e)');
+  test_valid_selector(':not(:host)');
+  test_valid_selector(':not(:host(.a))');
+  test_valid_selector(':host(:not(.a))');
+  test_valid_selector(':not(:host(:not(.a)))');
+  test_valid_selector(':not([disabled][selected])', ':not([disabled][selected])');
+  test_valid_selector(':not([disabled],[selected])', ':not([disabled], [selected])');
+
+  test_invalid_selector(':not()');
+  test_invalid_selector(':not(:not())');
+  test_invalid_selector(':not(::before)');
+  test_invalid_selector(':not(:unknownpseudo)');
+  test_invalid_selector(':not(.a, :unknownpseudo)');
+  test_invalid_selector(':not(:unknownpseudo, .a)');
+  test_invalid_selector(':host(:not(.a .b))');
+</script>