Add test

Author: tellthemachines

phpunit/block-supports/layout-test.php

@@ -564,6 +564,33 @@ public function data_layout_support_flag_renders_classnames_on_wrapper() {
 				),
 				'expected_output' => '<div class="wp-block-group is-layout-grid wp-container-core-group-is-layout-9d260ee2 wp-block-group-is-layout-grid"></div>',
 			),
+			/*
+			 * When the first innerContent chunk contains a sibling element (one that fully opens
+			 * and closes before the inner blocks), the layout classes must be added to the outer
+			 * container — not to the sibling. The sibling's class was incorrectly chosen by the
+			 * previous logic because it was the last class encountered while scanning the chunk.
+			 */
+			'outer wrapper targeted when sibling element precedes inner blocks' => array(
+				'args'            => array(
+					'block_content' => '<div class="wp-block-group"><div class="wp-block-group__header">Header</div><p>Inner block</p></div>',
+					'block'         => array(
+						'blockName'    => 'core/group',
+						'attrs'        => array(
+							'layout' => array(
+								'type' => 'default',
+							),
+						),
+						'innerBlocks'  => array(),
+						'innerHTML'    => '<div class="wp-block-group"><div class="wp-block-group__header">Header</div><p>Inner block</p></div>',
+						'innerContent' => array(
+							'<div class="wp-block-group"><div class="wp-block-group__header">Header</div>',
+							null,
+							'</div>',
+						),
+					),
+				),
+				'expected_output' => '<div class="wp-block-group is-layout-flow wp-block-group-is-layout-flow"><div class="wp-block-group__header">Header</div><p>Inner block</p></div>',
+			),
 		);
 	}