diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 1cc4026cf..33b5a75cc 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -5,27 +5,18 @@
  * @package PWA
  */
 
-define( 'TESTS_PLUGIN_DIR', dirname( __DIR__ ) );
+use Yoast\WPTestUtils\WPIntegration;
 
-// Detect where to load the WordPress tests environment from.
-if ( false !== getenv( 'WP_TESTS_DIR' ) ) {
-	$_test_root = getenv( 'WP_TESTS_DIR' );
-} elseif ( false !== getenv( 'WP_DEVELOP_DIR' ) ) {
-	$_test_root = getenv( 'WP_DEVELOP_DIR' ) . '/tests/phpunit';
-} elseif ( file_exists( '/tmp/wordpress-tests/includes/bootstrap.php' ) ) {
-	$_test_root = '/tmp/wordpress-tests';
-} elseif ( file_exists( '/var/www/wordpress-develop/tests/phpunit' ) ) {
-	$_test_root = '/var/www/wordpress-develop/tests/phpunit';
-} else {
-	$_test_root = dirname( dirname( dirname( dirname( TESTS_PLUGIN_DIR ) ) ) ) . '/tests/phpunit';
-}
+define( 'TESTS_PLUGIN_DIR', dirname( __DIR__ ) );
 
 // When run in wp-env context, set the test config file path.
 if ( ! defined( 'WP_TESTS_CONFIG_FILE_PATH' ) && false !== getenv( 'WP_PHPUNIT__TESTS_CONFIG' ) ) {
 	define( 'WP_TESTS_CONFIG_FILE_PATH', getenv( 'WP_PHPUNIT__TESTS_CONFIG' ) );
 }
 
-require $_test_root . '/includes/functions.php';
+require_once TESTS_PLUGIN_DIR . '/vendor/yoast/wp-test-utils/src/WPIntegration/bootstrap-functions.php';
+$_tests_dir = WPIntegration\get_path_to_wp_test_dir();
+require_once $_tests_dir . '/includes/functions.php';
 
 /**
  * Force plugins defined in a constant (supplied by phpunit.xml) to be active at runtime.
@@ -67,13 +58,23 @@ function pwa_unit_test_load_plugin_file() {
 define( 'WP_CLI_ROOT', TESTS_PLUGIN_DIR . '/vendor/wp-cli/wp-cli' );
 define( 'WP_CLI_VENDOR_DIR', TESTS_PLUGIN_DIR . '/vendor' );
 
+/*
+ * Load WordPress, which will load the Composer autoload file, and load the MockObject autoloader after that.
+ */
+WPIntegration\bootstrap_it();
+
 if ( file_exists( WP_CLI_ROOT . '/php/utils.php' ) ) {
 	require_once WP_CLI_ROOT . '/php/utils.php';
-	WP_CLI\Utils\load_dependencies();
 
 	$logger = new WP_CLI\Loggers\Regular( true );
 	WP_CLI::set_logger( $logger );
 }
 
-// Start up the WP testing environment.
-require $_test_root . '/includes/bootstrap.php';
+// Fix up the SERVER_PORT which was just clobbered by tests_reset__SERVER().
+if ( defined( 'WP_HOME' ) ) {
+	$port = wp_parse_url( WP_HOME, PHP_URL_PORT );
+	if ( ! $port ) {
+		$port = '80';
+	}
+	$_SERVER['SERVER_PORT'] = $port;
+}