public function testVoid()
 {
     // First create transaction to void.
     $amount = rand(1, 1000);
     $sale = new Request();
     $sale->setFields(array('amount' => $amount, 'card_num' => '6011000000000012', 'exp_date' => '0415'));
     $response = $sale->authorizeAndCapture();
     $this->assertTrue($response->approved);
     $void = new Request();
     $void->setFields(array('amount' => $amount, 'card_num' => '6011000000000012', 'trans_id' => $response->transaction_id));
     $void_response = $void->Void();
     $this->assertTrue($void_response->approved);
 }