title: How can I resolve the error Attempting to load class "MockStorageStrategy"?
body: <p>I'm stuck on an error that I can't solve, I need help please.</p>
  <p>Attempted to load class &quot;MockStorageStrategy&quot; from namespace &quot;MangoPay\Tests\Mocks&quot;.
  Did you forget a &quot;use&quot; statement for another namespace?</p>
  <p><img src="https://i.stack.imgur.com/FEnsZ.jpg" alt="error message" /></p>
  <p>my code:</p>
  <pre><code>&lt;?php
  
  namespace App\Service;
  
  use Symfony\Contracts\HttpClient\HttpClientInterface;
  use App\Entity\User;
  use MangoPay;
  use MangoPay\Tests\Mocks\MockStorageStrategy;
  
  class CallApiService
  {
      private $mangoPayApi;
      private $client;
  
      public function __construct(HttpClientInterface $httpClient)
      {
          $this-&gt;client = $httpClient;
          $this-&gt;mangoPayApi = new MangoPay\MangoPayApi();
          $this-&gt;mangoPayApi-&gt;Config-&gt;ClientId = $_ENV['CLIENT_ID'];
          $this-&gt;mangoPayApi-&gt;Config-&gt;ClientPassword = $_ENV['API_KEY'];
          // $this-&gt;mangoPayApi-&gt;Config-&gt;TemporaryFolder = '/some/path/';
          $this-&gt;mangoPayApi-&gt;OAuthTokenManager-&gt;RegisterCustomStorageStrategy(new MockStorageStrategy());
          //$this-&gt;mangoPayApi-&gt;Config-&gt;BaseUrl = 'https://api.sandbox.mangopay.com';
      }
  
      public function createProfilMango($form)
      {
          $userMango = $this-&gt;client-&gt;request(
              'POST',
              'https://api.sandbox.mangopay.com/v2.01/' . '%env(CLIENT_ID)%' . '/users/natural',
              [
                  $UserNatural = new MangoPay\UserNatural(),
                  $UserNatural-&gt;FirstName = $form['firstname']-&gt;getData(),
                  $UserNatural-&gt;LastName = $form['lastname']-&gt;getData(),
                  $UserNatural-&gt;Email = $form['email']-&gt;getData(),
                  $UserNatural-&gt;Address = new \MangoPay\Address(),
                  $UserNatural-&gt;Address-&gt;AddressLine1 = $form['streetNumber']-&gt;getData() . $form['address']-&gt;getData(),
                  $UserNatural-&gt;Address-&gt;AddressLine2 = &quot;&quot;,
                  $UserNatural-&gt;Address-&gt;City = $form['city']-&gt;getData(),
                  $UserNatural-&gt;Address-&gt;Region = &quot;&quot;,
                  $UserNatural-&gt;Address-&gt;PostalCode = $form['zipCode']-&gt;getData(),
                  $UserNatural-&gt;Address-&gt;Country = &quot;FR&quot;,
                  $UserNatural-&gt;Birthday = $form['birthday']-&gt;getData(),
                  $UserNatural-&gt;Nationality = $form['nationality']-&gt;getData(),
                  $UserNatural-&gt;CountryOfResidence = &quot;FR&quot;,
                  $Result = $this-&gt;mangoPayApi-&gt;Users-&gt;Create($UserNatural),
              ]
          );
  
          return $userMango;
      }
  }
  </code></pre>
  <p>The namespace has been checked and it is correct, concerning the dependencies the http-client and mangopay/php-sdk-v2 have been installed.</p>