diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessor.php b/tests/phpunit/tests/html-api/wpHtmlProcessor.php
index 120cf354e9b0b..49010607e7781 100644
--- a/tests/phpunit/tests/html-api/wpHtmlProcessor.php
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessor.php
@@ -193,7 +193,7 @@ public function test_cannot_nest_void_tags( $tag_name ) {
 	 *
 	 * @return array[]
 	 */
-	public function data_void_tags() {
+	public static function data_void_tags() {
 		return array(
 			'AREA'   => array( 'AREA' ),
 			'BASE'   => array( 'BASE' ),
@@ -237,7 +237,7 @@ public function test_step_in_body_fails_on_unsupported_tags( $tag_name ) {
 	 *
 	 * @return array[]
 	 */
-	public function data_unsupported_special_in_body_tags() {
+	public static function data_unsupported_special_in_body_tags() {
 		return array(
 			'APPLET'    => array( 'APPLET' ),
 			'BASE'      => array( 'BASE' ),
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorBreadcrumbs.php b/tests/phpunit/tests/html-api/wpHtmlProcessorBreadcrumbs.php
index 06576ba1e6123..1488be91654a7 100644
--- a/tests/phpunit/tests/html-api/wpHtmlProcessorBreadcrumbs.php
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorBreadcrumbs.php
@@ -34,7 +34,7 @@ public function test_navigates_into_normative_html_for_supported_elements( $html
 	 *
 	 * @return array[]
 	 */
-	public function data_single_tag_of_supported_elements() {
+	public static function data_single_tag_of_supported_elements() {
 		$supported_elements = array(
 			'A',
 			'ABBR',
@@ -165,7 +165,7 @@ public function test_fails_when_encountering_unsupported_tag( $html ) {
 	 *
 	 * @return array[]
 	 */
-	public function data_unsupported_elements() {
+	public static function data_unsupported_elements() {
 		$unsupported_elements = array(
 			'APPLET', // Deprecated.
 			'BASE',
@@ -244,7 +244,7 @@ public function test_fails_when_encountering_unsupported_markup( $html, $descrip
 	 *
 	 * @return array[]
 	 */
-	public function data_unsupported_markup() {
+	public static function data_unsupported_markup() {
 		return array(
 			'A with formatting following unclosed A' => array(
 				'<a><strong>Click <a supported><big unsupported>Here</big></a></strong></a>',
@@ -310,7 +310,7 @@ public function test_reports_correct_breadcrumbs_for_html( $html, $breadcrumbs,
 	 *
 	 * @return array[]
 	 */
-	public function data_html_target_with_breadcrumbs() {
+	public static function data_html_target_with_breadcrumbs() {
 		return array(
 			'Simple IMG tag'                        => array( '<img target>', array( 'HTML', 'BODY', 'IMG' ), 1 ),
 			'Two sibling IMG tags'                  => array( '<img><img target>', array( 'HTML', 'BODY', 'IMG' ), 2 ),
@@ -393,7 +393,7 @@ public function test_reports_if_tag_matches_breadcrumbs_of_various_specificity(
 	 *
 	 * @return array[].
 	 */
-	public function data_html_with_breadcrumbs_of_various_specificity() {
+	public static function data_html_with_breadcrumbs_of_various_specificity() {
 		return array(
 			// Test with void elements.
 			'Inner IMG'                               => array( '<div><span><figure><img target></figure></span></div>', array( 'span', 'figure', 'img' ), true ),
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorSemanticRules.php b/tests/phpunit/tests/html-api/wpHtmlProcessorSemanticRules.php
index ca1acb2660e29..7362a588cf3f4 100644
--- a/tests/phpunit/tests/html-api/wpHtmlProcessorSemanticRules.php
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorSemanticRules.php
@@ -79,7 +79,7 @@ public function test_in_body_article_group_can_nest_inside_itself( $tag_name ) {
 	 *
 	 * @return array[].
 	 */
-	public function data_article_container_group() {
+	public static function data_article_container_group() {
 		$group = array();
 
 		foreach (
@@ -274,7 +274,7 @@ public function test_in_body_heading_element_closes_open_p_tag( $tag_name ) {
 	 *
 	 * @return array[].
 	 */
-	public function data_heading_elements() {
+	public static function data_heading_elements() {
 		return array(
 			'H1' => array( 'H1' ),
 			'H2' => array( 'H2' ),
@@ -328,7 +328,7 @@ public function test_in_body_heading_element_closes_other_heading_elements( $fir
 	 *
 	 * @return array[]
 	 */
-	public function data_heading_combinations() {
+	public static function data_heading_combinations() {
 		$headings = array( 'H1', 'H2', 'H3', 'H4', 'H5', 'H6' );
 
 		$combinations = array();
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessorSemanticRulesHeadingElements.php b/tests/phpunit/tests/html-api/wpHtmlProcessorSemanticRulesHeadingElements.php
index d8d70acb61e76..b33c6e072dfb1 100644
--- a/tests/phpunit/tests/html-api/wpHtmlProcessorSemanticRulesHeadingElements.php
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessorSemanticRulesHeadingElements.php
@@ -53,7 +53,7 @@ public function test_in_body_heading_element_closes_open_p_tag( $tag_name ) {
 	 *
 	 * @return array[].
 	 */
-	public function data_heading_elements() {
+	public static function data_heading_elements() {
 		return array(
 			'H1' => array( 'H1' ),
 			'H2' => array( 'H2' ),
@@ -109,7 +109,7 @@ public function test_in_body_heading_element_closes_other_heading_elements( $fir
 	 *
 	 * @return array[]
 	 */
-	public function data_heading_combinations() {
+	public static function data_heading_combinations() {
 		$headings = array( 'H1', 'H2', 'H3', 'H4', 'H5', 'H6' );
 
 		$combinations = array();
diff --git a/tests/phpunit/tests/html-api/wpHtmlTagProcessor-token-scanning.php b/tests/phpunit/tests/html-api/wpHtmlTagProcessor-token-scanning.php
index 538144910550f..efcc4a01f745f 100644
--- a/tests/phpunit/tests/html-api/wpHtmlTagProcessor-token-scanning.php
+++ b/tests/phpunit/tests/html-api/wpHtmlTagProcessor-token-scanning.php
@@ -295,7 +295,7 @@ public function test_basic_assertion_rawtext_elements( $tag_name ) {
 	 *
 	 * @return array[].
 	 */
-	public function data_rawtext_elements() {
+	public static function data_rawtext_elements() {
 		return array(
 			'IFRAME'   => array( 'IFRAME' ),
 			'NOEMBED'  => array( 'NOEMBED' ),
@@ -542,7 +542,7 @@ public function test_basic_assertion_common_comments( $html, $text ) {
 	 *
 	 * @return array[].
 	 */
-	public function data_common_comments() {
+	public static function data_common_comments() {
 		return array(
 			'Shortest comment'        => array( '<!-->', '' ),
 			'Short comment'           => array( '<!--->', '' ),
diff --git a/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php b/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php
index 2121ffa221fc9..5375a2fca0ebf 100644
--- a/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php
+++ b/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php
@@ -77,7 +77,7 @@ public function test_has_self_closing_flag_matches_input_html( $html, $flag_is_s
 	 *
 	 * @return array[]
 	 */
-	public function data_has_self_closing_flag() {
+	public static function data_has_self_closing_flag() {
 		return array(
 			// These should not have a self-closer, and will leave an element un-closed if it's assumed they are self-closing.
 			'Self-closing flag on non-void HTML element' => array( '<div />', true ),
@@ -259,7 +259,7 @@ public function test_attributes_parser_is_case_insensitive_for_attributes_withou
 	 *
 	 * @return array[].
 	 */
-	public function data_attribute_name_case_variants() {
+	public static function data_attribute_name_case_variants() {
 		return array(
 			array( 'DATA-enabled' ),
 			array( 'data-enabled' ),
@@ -724,7 +724,7 @@ public function test_set_attribute_prevents_xss( $attribute_value ) {
 	 *
 	 * @return string[][].
 	 */
-	public function data_set_attribute_prevents_xss() {
+	public static function data_set_attribute_prevents_xss() {
 		return array(
 			array( '"' ),
 			array( '&quot;' ),
@@ -1146,7 +1146,7 @@ public function test_previous_duplicated_attributes_are_not_removed_on_successiv
 	 *
 	 * @return array[].
 	 */
-	public function data_html_with_duplicated_attributes() {
+	public static function data_html_with_duplicated_attributes() {
 		return array(
 			'Double attributes'               => array( '<div id=one id=two>', 'id' ),
 			'Triple attributes'               => array( '<div id=one id=two id=three>', 'id' ),
@@ -1801,7 +1801,7 @@ public function test_next_tag_ignores_script_tag_contents( $script_then_div ) {
 	 *
 	 * @return array[].
 	 */
-	public function data_next_tag_ignores_script_tag_contents() {
+	public static function data_next_tag_ignores_script_tag_contents() {
 		return array(
 			'Simple script tag'                          => array(
 				'<script><span class="d-none d-md-inline">Back to notifications</span></script><div></div>',
@@ -1878,7 +1878,7 @@ public function test_next_tag_ignores_invalid_first_character_of_tag_name_commen
 	 *
 	 * @return array[]
 	 */
-	public function data_next_tag_ignores_invalid_first_character_of_tag_name_comments() {
+	public static function data_next_tag_ignores_invalid_first_character_of_tag_name_comments() {
 		return array(
 			'Invalid tag openers as normal text'           => array(
 				'<ul><li><div class=start>I <3 when outflow > inflow</div><img class=end></li></ul>',
@@ -1917,7 +1917,7 @@ public function test_next_tag_ignores_contents_of_rcdata_tag( $rcdata_then_div,
 	 *
 	 * @return array[]
 	 */
-	public function data_next_tag_ignores_contents_of_rcdata_tag() {
+	public static function data_next_tag_ignores_contents_of_rcdata_tag() {
 		return array(
 			'simple textarea'                          => array(
 				'rcdata_then_div' => '<textarea><span class="d-none d-md-inline">Back to notifications</span></textarea><div></div>',
@@ -1996,7 +1996,7 @@ public function test_next_tag_ignores_contents_of_rawtext_tags( $rawtext_element
 	 *
 	 * @return array[].
 	 */
-	public function data_next_tag_ignores_contents_of_rawtext_tags() {
+	public static function data_next_tag_ignores_contents_of_rawtext_tags() {
 		return array(
 			'IFRAME'           => array( '<iframe><section>Inside</section></iframe><section target>' ),
 			'NOEMBED'          => array( '<noembed><p></p></noembed><div target>' ),
@@ -2135,7 +2135,7 @@ public function test_has_class_handles_expected_class_name_variations( $html, $s
 	 *
 	 * @return array[]
 	 */
-	public function data_html_with_variations_of_class_values_and_sought_class_names() {
+	public static function data_html_with_variations_of_class_values_and_sought_class_names() {
 		return array(
 			'Tag without any classes'      => array( '<div>', 'foo', false ),
 			'Tag with boolean class'       => array( '<img class>', 'foo', false ),
@@ -2202,7 +2202,7 @@ public function test_documents_may_end_with_unclosed_comment( $html_ending_befor
 	 *
 	 * @return array[]
 	 */
-	public function data_html_with_unclosed_comments() {
+	public static function data_html_with_unclosed_comments() {
 		return array(
 			'Shortest open valid comment'      => array( '<!--' ),
 			'Basic truncated comment'          => array( '<!-- this ends --' ),
@@ -2237,7 +2237,7 @@ public function test_closes_abrupt_closing_of_empty_comment( $html_with_after_ma
 	 *
 	 * @return array[]
 	 */
-	public function data_abruptly_closed_empty_comments() {
+	public static function data_abruptly_closed_empty_comments() {
 		return array(
 			'Empty comment with two dashes only' => array( '<hr><!--><hr id=after>' ),
 			'Empty comment with two dashes only, improperly closed' => array( '<hr><!--!><hr id=inside>--><hr id=after>' ),
@@ -2276,7 +2276,7 @@ public function test_skips_contents_of_script_and_rcdata_regions( $input_html )
 	 *
 	 * @return array[]
 	 */
-	public function data_skips_contents_of_script_and_rcdata_regions() {
+	public static function data_skips_contents_of_script_and_rcdata_regions() {
 		return array(
 			'Balanced SCRIPT tags'                => array( '<script>console.log("<div>");</script><div target><div>' ),
 			'Unexpected SCRIPT closer after DIV'  => array( 'console.log("<div target>")</script><div><div>' ),
@@ -2357,7 +2357,7 @@ public function test_next_tag_returns_false_when_there_are_no_tags( $html_withou
 	 *
 	 * @return array[]
 	 */
-	public function data_html_without_tags() {
+	public static function data_html_without_tags() {
 		return array(
 			'DOCTYPE declaration'    => array( '<!DOCTYPE html>Just some HTML' ),
 			'No tags'                => array( 'this is nothing more than a text node' ),
@@ -2400,7 +2400,7 @@ public function test_next_tag_returns_false_for_incomplete_syntax_elements( $inc
 	 *
 	 * @return array[]
 	 */
-	public function data_incomplete_syntax_elements() {
+	public static function data_incomplete_syntax_elements() {
 		return array(
 			'Incomplete tag name'                  => array( '<swit' ),
 			'Incomplete tag (no attributes)'       => array( '<div' ),
@@ -2485,7 +2485,7 @@ public function test_updating_attributes( $html, $expected ) {
 	 *
 	 * @return array[]
 	 */
-	public function data_updating_attributes() {
+	public static function data_updating_attributes() {
 		return array(
 			'tags inside of a comment' => array(
 				'input'    => '<!-- this is a comment. no <strong>tags</strong> allowed --><span>test</span>',
@@ -2549,7 +2549,7 @@ public function test_updating_attributes_in_malformed_html( $html, $expected ) {
 	 *
 	 * @return array[]
 	 */
-	public function data_updating_attributes_in_malformed_html() {
+	public static function data_updating_attributes_in_malformed_html() {
 		return array(
 			'Invalid entity inside attribute value'        => array(
 				'input'    => '<img src="https://s0.wp.com/i/atat.png" title="&; First &lt;title&gt; is &notit;" TITLE="second title" title="An Imperial &imperial; AT-AT"><span>test</span>',