Braintree\Gateway::subscription PHP Method

    public function subscription()
    {
        return new SubscriptionGateway($this);
    }

 public function testGatewayCreate_whenSuccessful()
 {
     $creditCard = SubscriptionHelper::createCreditCard();
     $plan = SubscriptionHelper::triallessPlan();
     $gateway = new Braintree\Gateway(['environment' => 'development', 'merchantId' => 'integration_merchant_id', 'publicKey' => 'integration_public_key', 'privateKey' => 'integration_private_key']);
     $result = $gateway->subscription()->create(['paymentMethodToken' => $creditCard->token, 'planId' => $plan['id']]);
     Test\Helper::assertPrintable($result);
     $this->assertTrue($result->success);
     $subscription = $result->subscription;
     $this->assertEquals($creditCard->token, $subscription->paymentMethodToken);
     $this->assertEquals(0, $subscription->failureCount);
     $this->assertEquals($plan['id'], $subscription->planId);
     $this->assertEquals(Test\Helper::defaultMerchantAccountId(), $subscription->merchantAccountId);
     $this->assertEquals(Braintree\Subscription::ACTIVE, $subscription->status);
 }