Update test_add_registered_block_styles_to_theme_data to register variations

Author: oandregal

tests/phpunit/tests/block-supports/block-style-variations.php

@@ -65,6 +65,11 @@ public function filter_set_theme_root() {
 	public function test_add_registered_block_styles_to_theme_data() {
 		switch_theme( 'block-theme' );
 
+		// Trigger block style registration that occurs on `init` action.
+		// do_action( 'init' ) could be used here however this direct call
+		// means only the updates being tested are performed.
+		wp_register_block_style_variations_from_theme();
+
 		$variation_styles_data = array(
 			'color'    => array(
 				'background' => 'darkslateblue',