diff --git a/src/admin-notifications.php b/src/admin-notifications.php
index db6c02c..4aaff16 100644
--- a/src/admin-notifications.php
+++ b/src/admin-notifications.php
@@ -20,7 +20,7 @@ class Admin_Notifications implements Integration {
 	 * @return void
 	 */
 	public function add_hooks() {
-		\add_action( 'Yoast\WP\Test_Helper\notification', [ $this, 'add_notification' ], 10, 2 );
+		\add_action( 'Yoast\WP\Test_Helper\notification', [ $this, 'add_notification' ] );
 		\add_action( 'Yoast\WP\Test_Helper\notifications', [ $this, 'display_notifications' ] );
 	}
 
diff --git a/src/admin-page.php b/src/admin-page.php
index 12c486b..8087d53 100644
--- a/src/admin-page.php
+++ b/src/admin-page.php
@@ -44,7 +44,7 @@ public function add_assets() {
 		\wp_enqueue_style(
 			'yoast-test-admin-style',
 			\plugin_dir_url( \YOAST_TEST_HELPER_FILE ) . 'assets/css/admin.css',
-			null,
+			[],
 			\YOAST_TEST_HELPER_VERSION
 		);
 		\wp_enqueue_script( 'masonry' );
diff --git a/src/downgrader.php b/src/downgrader.php
index e65d9ea..cc849f8 100644
--- a/src/downgrader.php
+++ b/src/downgrader.php
@@ -151,7 +151,7 @@ protected function downgrade( $target_version ) {
 				$adapter->remove_version( $version );
 				$adapter->commit_transaction();
 			} catch ( Exception $e ) {
-				$this->adapter->rollback_transaction();
+				$adapter->rollback_transaction();
 
 				throw new Exception(
 					\sprintf(
diff --git a/src/feature-toggler.php b/src/feature-toggler.php
index 15fa9a4..3ad81d6 100644
--- a/src/feature-toggler.php
+++ b/src/feature-toggler.php
@@ -36,7 +36,7 @@ public function __construct( Option $option ) {
 	 * @return void
 	 */
 	public function add_hooks() {
-		\add_action( 'wpseo_enable_feature', [ $this, 'enable_features' ] );
+		\add_filter( 'wpseo_enable_feature', [ $this, 'enable_features' ] );
 
 		\add_action(
 			'admin_post_yoast_seo_feature_toggler',
diff --git a/src/plugin-toggler.php b/src/plugin-toggler.php
index d5f268e..08d199e 100644
--- a/src/plugin-toggler.php
+++ b/src/plugin-toggler.php
@@ -394,7 +394,7 @@ private function activate_plugin( $group, $plugin ) {
 		}
 
 		$plugin_path = $this->plugin_groups[ $group ][ $plugin ];
-		\activate_plugin( \plugin_basename( $plugin_path ), null, false, true );
+		\activate_plugin( \plugin_basename( $plugin_path ), '', false, true );
 	}
 
 	/**
@@ -431,6 +431,8 @@ private function verify_nonce() {
 		if ( isset( $_GET['ajax_nonce'] ) && \wp_verify_nonce( $_GET['ajax_nonce'], 'yoast-plugin-toggle' ) ) {
 			return true;
 		}
+
+		return false;
 	}
 
 	/**