public function phpunit_compat() {

		if ( class_exists( 'PHPUnit\Runner\Version' ) ) {
			
			$tests_dir = $this->get_wp_tests_dir();

			// Back-compat for older WP versions.
			if ( file_exists( $tests_dir . '/includes/phpunit6-compat.php' ) ) {
			
				/**
				 * Compatibility with PHPUnit 6+.
				 *
				 * @since 0.3.2
				 */
				require_once $tests_dir . '/includes/phpunit6-compat.php';

			} else {
			
				/**
				 * Compatibility with PHPUnit 6+.
				 *
				 * @since 0.3.6
				 */
				require_once $tests_dir . '/includes/phpunit6/compat.php';
			}
			
			class_alias(
				'PHPUnit\Framework\Constraint\Constraint'
				, 'PHPUnit_Framework_Constraint'
			);
		}
	}