diff -u b/core/modules/user/tests/src/Functional/UserLoginTest.php b/core/modules/user/tests/src/Functional/UserLoginTest.php
--- b/core/modules/user/tests/src/Functional/UserLoginTest.php
+++ b/core/modules/user/tests/src/Functional/UserLoginTest.php
@@ -180,7 +180,7 @@
    */
   public function doPasswordLengthLogin($account, $current_password, $length) {
     $session = $this->assertSession();
-    $new_password = user_password($length);
+    $new_password = \Drupal::service('password_generator')->generate($length);
     $uid = $account->id();
     $edit = [
       'current_pass' => $current_password,