public function testAuthorizeFailure()
{
$this->setMockHttpResponse('ExpressPurchaseFailure.txt');
$response = $this->gateway->authorize($this->options)->send();
$this->assertFalse($response->isPending());
$this->assertFalse($response->isSuccessful());
$this->assertFalse($response->isRedirect());
$this->assertNull($response->getTransactionReference());
$this->assertSame('This transaction cannot be processed. The amount to be charged is zero.', $response->getMessage());
}