refund() public static method

public static refund ( )
 public function test_multipleValueNode_type_withRefund()
 {
     $customer = Braintree\Customer::createNoValidate();
     $creditCard = Braintree\CreditCard::create(['customerId' => $customer->id, 'cardholderName' => 'Joe Everyman' . rand(), 'number' => '5105105105105100', 'expirationDate' => '05/12'])->creditCard;
     $sale = Braintree\Transaction::saleNoValidate(['amount' => Braintree\Test\TransactionAmounts::$authorize, 'paymentMethodToken' => $creditCard->token, 'options' => ['submitForSettlement' => true]]);
     $http = new Braintree\Http(Braintree\Configuration::$global);
     $path = Braintree\Configuration::$global->merchantPath() . '/transactions/' . $sale->id . '/settle';
     $http->put($path);
     $refund = Braintree\Transaction::refund($sale->id)->transaction;
     $credit = Braintree\Transaction::creditNoValidate(['amount' => '100.00', 'paymentMethodToken' => $creditCard->token]);
     $collection = Braintree\Transaction::search([Braintree\TransactionSearch::creditCardCardholderName()->is($creditCard->cardholderName), Braintree\TransactionSearch::type()->is($credit->type), Braintree\TransactionSearch::refund()->is(True)]);
     $this->assertEquals(1, $collection->maximumCount());
     $this->assertEquals($refund->id, $collection->firstItem()->id);
     $collection = Braintree\Transaction::search([Braintree\TransactionSearch::creditCardCardholderName()->is($creditCard->cardholderName), Braintree\TransactionSearch::type()->is($credit->type), Braintree\TransactionSearch::refund()->is(False)]);
     $this->assertEquals(1, $collection->maximumCount());
     $this->assertEquals($credit->id, $collection->firstItem()->id);
 }