diff --git a/tests/phpunit/tests/html-api/wpCssCompoundSelectorList.php b/tests/phpunit/tests/html-api/wpCssCompoundSelectorList.php
index 715e0e26bc9cd..6d1b142c17ea9 100644
--- a/tests/phpunit/tests/html-api/wpCssCompoundSelectorList.php
+++ b/tests/phpunit/tests/html-api/wpCssCompoundSelectorList.php
@@ -331,45 +331,53 @@ public function test_parse_attribute(
 	 */
 	public static function data_attribute_selectors(): array {
 		return array(
-			'[href]'                   => array( '[href]', 'href', null, null, null, '' ),
-			'[href] type'              => array( '[href] type', 'href', null, null, null, ' type' ),
-			'[href]#id'                => array( '[href]#id', 'href', null, null, null, '#id' ),
-			'[href].class'             => array( '[href].class', 'href', null, null, null, '.class' ),
-			'[href][href2]'            => array( '[href][href2]', 'href', null, null, null, '[href2]' ),
-			'[\n href\t\r]'            => array( "[\n href\t\r]", 'href', null, null, null, '' ),
-			'[href=foo]'               => array( '[href=foo]', 'href', WP_CSS_Attribute_Selector::MATCH_EXACT, 'foo', null, '' ),
-			'[href \n =   bar   ]'     => array( "[href \n =   bar   ]", 'href', WP_CSS_Attribute_Selector::MATCH_EXACT, 'bar', null, '' ),
-			'[href \n ^=   baz   ]'    => array( "[href \n ^=   baz   ]", 'href', WP_CSS_Attribute_Selector::MATCH_PREFIXED_BY, 'baz', null, '' ),
-
-			'[match $= insensitive i]' => array( '[match $= insensitive i]', 'match', WP_CSS_Attribute_Selector::MATCH_SUFFIXED_BY, 'insensitive', WP_CSS_Attribute_Selector::MODIFIER_CASE_INSENSITIVE, '' ),
-			'[match|=sensitive s]'     => array( '[match|=sensitive s]', 'match', WP_CSS_Attribute_Selector::MATCH_EXACT_OR_EXACT_WITH_HYPHEN, 'sensitive', WP_CSS_Attribute_Selector::MODIFIER_CASE_SENSITIVE, '' ),
-			'[att=val I]'              => array( '[att=val I]', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, 'val', WP_CSS_Attribute_Selector::MODIFIER_CASE_INSENSITIVE, '' ),
-			'[att=val S]'              => array( '[att=val S]', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, 'val', WP_CSS_Attribute_Selector::MODIFIER_CASE_SENSITIVE, '' ),
-
-			'[match~="quoted[][]"]'    => array( '[match~="quoted[][]"]', 'match', WP_CSS_Attribute_Selector::MATCH_ONE_OF_EXACT, 'quoted[][]', null, '' ),
-			"[match$='quoted!{}']"     => array( "[match$='quoted!{}']", 'match', WP_CSS_Attribute_Selector::MATCH_SUFFIXED_BY, 'quoted!{}', null, '' ),
-			"[match*='quoted's]"       => array( "[match*='quoted's]", 'match', WP_CSS_Attribute_Selector::MATCH_CONTAINS, 'quoted', WP_CSS_Attribute_Selector::MODIFIER_CASE_SENSITIVE, '' ),
-
-			'[escape-nl="foo\\nbar"]'  => array( "[escape-nl='foo\\\nbar']", 'escape-nl', WP_CSS_Attribute_Selector::MATCH_EXACT, 'foobar', null, '' ),
-			'[escape-seq="\\31 23"]'   => array( "[escape-seq='\\31 23']", 'escape-seq', WP_CSS_Attribute_Selector::MATCH_EXACT, '123', null, '' ),
+			'[href]'                     => array( '[href]', 'href', null, null, null, '' ),
+			'[href] type'                => array( '[href] type', 'href', null, null, null, ' type' ),
+			'[href]#id'                  => array( '[href]#id', 'href', null, null, null, '#id' ),
+			'[href].class'               => array( '[href].class', 'href', null, null, null, '.class' ),
+			'[href][href2]'              => array( '[href][href2]', 'href', null, null, null, '[href2]' ),
+			'[\n href\t\r]'              => array( "[\n href\t\r]", 'href', null, null, null, '' ),
+			'[href=foo]'                 => array( '[href=foo]', 'href', WP_CSS_Attribute_Selector::MATCH_EXACT, 'foo', null, '' ),
+			'[href \n =   bar   ]'       => array( "[href \n =   bar   ]", 'href', WP_CSS_Attribute_Selector::MATCH_EXACT, 'bar', null, '' ),
+			'[href \n ^=   baz   ]'      => array( "[href \n ^=   baz   ]", 'href', WP_CSS_Attribute_Selector::MATCH_PREFIXED_BY, 'baz', null, '' ),
+
+			'[match $= insensitive i]'   => array( '[match $= insensitive i]', 'match', WP_CSS_Attribute_Selector::MATCH_SUFFIXED_BY, 'insensitive', WP_CSS_Attribute_Selector::MODIFIER_CASE_INSENSITIVE, '' ),
+			'[match|=sensitive s]'       => array( '[match|=sensitive s]', 'match', WP_CSS_Attribute_Selector::MATCH_EXACT_OR_EXACT_WITH_HYPHEN, 'sensitive', WP_CSS_Attribute_Selector::MODIFIER_CASE_SENSITIVE, '' ),
+			'[att=val I]'                => array( '[att=val I]', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, 'val', WP_CSS_Attribute_Selector::MODIFIER_CASE_INSENSITIVE, '' ),
+			'[att=val S]'                => array( '[att=val S]', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, 'val', WP_CSS_Attribute_Selector::MODIFIER_CASE_SENSITIVE, '' ),
+
+			'[match~="quoted[][]"]'      => array( '[match~="quoted[][]"]', 'match', WP_CSS_Attribute_Selector::MATCH_ONE_OF_EXACT, 'quoted[][]', null, '' ),
+			"[match$='quoted!{}']"       => array( "[match$='quoted!{}']", 'match', WP_CSS_Attribute_Selector::MATCH_SUFFIXED_BY, 'quoted!{}', null, '' ),
+			"[match*='quoted's]"         => array( "[match*='quoted's]", 'match', WP_CSS_Attribute_Selector::MATCH_CONTAINS, 'quoted', WP_CSS_Attribute_Selector::MODIFIER_CASE_SENSITIVE, '' ),
+
+			'[escape-nl="foo\\nbar"]'    => array( "[escape-nl='foo\\\nbar']", 'escape-nl', WP_CSS_Attribute_Selector::MATCH_EXACT, 'foobar', null, '' ),
+			'[escape-seq="\\31 23"]'     => array( "[escape-seq='\\31 23']", 'escape-seq', WP_CSS_Attribute_Selector::MATCH_EXACT, '123', null, '' ),
+
+			'Unterminated: [att'         => array( '[att', 'att', null, null, null, '' ),
+			'Unterminated: [att="'       => array( '[att="', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, '', null, '' ),
+			'Unterminated: [att="\\"'    => array( '[att="\\"', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, '"', null, '' ),
+			'Unterminated: [att="x"'     => array( '[att="x"', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, 'x', null, '' ),
+			'Unterminated: [att="x\\"i]' => array( '[att="x\\"i]', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, 'x"i]', null, '' ),
+			'Unterminated: [att="x" i'   => array( '[att="x" i', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, 'x', WP_CSS_Attribute_Selector::MODIFIER_CASE_INSENSITIVE, '' ),
+			'Unterminated: [att = x i'   => array( '[att = x i', 'att', WP_CSS_Attribute_Selector::MATCH_EXACT, 'x', WP_CSS_Attribute_Selector::MODIFIER_CASE_INSENSITIVE, '' ),
 
 			// Invalid
-			'Invalid: (empty string)'  => array( '' ),
-			'Invalid: foo'             => array( 'foo' ),
-			'Invalid: [foo'            => array( '[foo' ),
-			'Invalid: [#foo]'          => array( '[#foo]' ),
-			'Invalid: [*|*]'           => array( '[*|*]' ),
-			'Invalid: [ns|*]'          => array( '[ns|*]' ),
-			'Invalid: [* |att]'        => array( '[* |att]' ),
-			'Invalid: [*| att]'        => array( '[*| att]' ),
-			'Invalid: [att * =]'       => array( '[att * =]' ),
-			'Invalid: [att+=val]'      => array( '[att+=val]' ),
-			'Invalid: [att=val '       => array( '[att=val ' ),
-			'Invalid: [att i]'         => array( '[att i]' ),
-			'Invalid: [att s]'         => array( '[att s]' ),
-			"Invalid: [att='val\\n']"  => array( "[att='val\n']" ),
-			'Invalid: [att=val i '     => array( '[att=val i ' ),
-			'Invalid: [att="val"ix'    => array( '[att="val"ix' ),
+			'Invalid: (empty string)'    => array( '' ),
+			'Invalid: foo'               => array( 'foo' ),
+			'Invalid: [foo'              => array( '[foo' ),
+			'Invalid: [#foo]'            => array( '[#foo]' ),
+			'Invalid: [*|*]'             => array( '[*|*]' ),
+			'Invalid: [ns|*]'            => array( '[ns|*]' ),
+			'Invalid: [* |att]'          => array( '[* |att]' ),
+			'Invalid: [*| att]'          => array( '[*| att]' ),
+			'Invalid: [att * =]'         => array( '[att * =]' ),
+			'Invalid: [att+=val]'        => array( '[att+=val]' ),
+			'Invalid: [att=val '         => array( '[att=val ' ),
+			'Invalid: [att i]'           => array( '[att i]' ),
+			'Invalid: [att s]'           => array( '[att s]' ),
+			"Invalid: [att='val\\n']"    => array( "[att='val\n']" ),
+			'Invalid: [att=val i '       => array( '[att=val i ' ),
+			'Invalid: [att="val"ix'      => array( '[att="val"ix' ),
 		);
 	}