PayPal\Exception\PayPalInvalidCredentialException::errorMessage PHP Метод

    public function errorMessage()
    {
        $errorMsg = 'Error on line ' . $this->getLine() . ' in ' . $this->getFile() . ': <b>' . $this->getMessage() . '</b>';
        return $errorMsg;
    }

 /**
  * @test
  */
 public function testErrorMessage()
 {
     $msg = $this->object->errorMessage();
     $this->assertContains('Error on line', $msg);
 }