diff --git a/projects/plugins/jetpack/tests/php/bootstrap.php b/projects/plugins/jetpack/tests/php/bootstrap.php
index be48273fb6c70..5462725146a14 100644
--- a/projects/plugins/jetpack/tests/php/bootstrap.php
+++ b/projects/plugins/jetpack/tests/php/bootstrap.php
@@ -87,6 +87,11 @@
 	echo "Disregard Core's -c tests/phpunit/multisite.xml notice below." . PHP_EOL;
 }
 
+if ( '1' !== getenv( 'JETPACK_TEST_WPCOMSH' ) ) {
+	echo 'To run tests with the WordPress.com Site Helper plugin activated and Atomic mode enabled,' . PHP_EOL;
+	echo 'prefix phpunit with JETPACK_TEST_WPCOMSH=1' . PHP_EOL;
+}
+
 if ( '1' !== getenv( 'JETPACK_TEST_WOOCOMMERCE' ) ) {
 	echo 'To run Jetpack woocommerce tests, prefix phpunit with JETPACK_TEST_WOOCOMMERCE=1' . PHP_EOL;
 } else {
@@ -104,7 +109,29 @@ function _manually_load_plugin() {
 
 	if ( '1' === getenv( 'JETPACK_TEST_WPCOMSH' ) ) {
 		define( 'IS_ATOMIC', true );
-		require __DIR__ . '/../../../../mu-plugins/wpcomsh/wpcomsh.php';
+		if ( getenv( 'GITHUB_ACTIONS' ) ) {
+
+			// Using plugin code installed by .github/files/setup-wordpress-env.sh.
+			require_once __DIR__ . '/../../../../mu-plugins/wpcomsh/wpcomsh.php';
+			require_once __DIR__ . '/../../../../mu-plugins/wpcomsh/vendor/autoload.php';
+		} else {
+			require_once __DIR__ . '/../../../wpcomsh/wpcomsh.php';
+			require_once __DIR__ . '/../../../wpcomsh/vendor/autoload.php';
+		}
+		\Automattic\Jetpack\Jetpack_Mu_Wpcom::init();
+
+		// We can't simulate plugins_loaded because it causes a loop, but we can call load methods.
+		$reflection = new ReflectionClass( '\Automattic\Jetpack\Jetpack_Mu_Wpcom' );
+		foreach ( $reflection->getMethods() as $method ) {
+
+			// Verbum comments calls code that's not available in single site environment.
+			if ( str_starts_with( $method->name, 'load_' ) ) {
+				if ( 'load_verbum_comments' === $method->name ) {
+					continue;
+				}
+				$method->invoke( null );
+			}
+		}
 	}
 	require __DIR__ . '/../../jetpack.php';
 	$jetpack = Jetpack::init();
diff --git a/projects/plugins/jetpack/tests/php/lib/class-wpcom-features.php b/projects/plugins/jetpack/tests/php/lib/class-wpcom-features.php
index b602c12962252..b0a5b81f64229 100644
--- a/projects/plugins/jetpack/tests/php/lib/class-wpcom-features.php
+++ b/projects/plugins/jetpack/tests/php/lib/class-wpcom-features.php
@@ -5,6 +5,10 @@
  * @package Jetpack
  */
 
+if ( class_exists( 'WPCOM_Features' ) ) {
+	return;
+}
+
 /**
  * Class WPCOM_Features.
  */
diff --git a/projects/plugins/jetpack/tests/php/lib/mock-functions.php b/projects/plugins/jetpack/tests/php/lib/mock-functions.php
index 0d67d385731c0..0d4ba3031df1f 100644
--- a/projects/plugins/jetpack/tests/php/lib/mock-functions.php
+++ b/projects/plugins/jetpack/tests/php/lib/mock-functions.php
@@ -21,7 +21,7 @@ function has_blog_sticker( $sticker ) {
 	function wp_cache_is_enabled() {}
 }
 
-if ( ! function_exists( 'wpcom_site_has_feature' ) && false === getenv( 'WITH_WPCOMSH' ) ) {
+if ( ! function_exists( 'wpcom_site_has_feature' ) && false === getenv( 'JETPACK_TEST_WPCOMSH' ) ) {
 	/**
 	 * Mock feature support.
 	 *