test.php

<?php

namespace Tests\Feature;

use App\User;
use Laravel\Cashier\SubscriptionBuilder;
use Tests\TestCase;

use function route;

class PlansTest extends TestCase
{
    public function testSubscriptionIsSuccessfullyCreatedWithCoupon()
    {
        // Disable the authentication middleware, we don't need it.
        $this->withoutMiddleware([Authenticate::class]);

        // Prepare request variables.
        $paymentMethodId = 'payment-method';
        $couponCode = 'SOME_COUPON';

        // Prepare the subscription builder mock.
        $subscriptionBuilder = $this->prophesize(SubscriptionBuilder::class);
        $subscriptionBuilder->withCoupon($couponCode)
            ->shouldBeCalled();
        $subscriptionBuilder->create($paymentMethodId)
            ->shouldBeCalled();

        // Prepare the user mock
        $user = $this->prophesize(User::class);
        $user->newSubscription('default', 'standard')
            ->shouldBeCalled()
            ->willReturn($subscriptionBuilder->reveal());

        // Perform the request as our user mock.
        $testRoute = route('plans.save', ['plan' => 'standard']);
        $response = $this->actingAs($user->reveal())
            ->post($testRoute, [
                'paymentMethodId' => $paymentMethodId,
                'couponCode'      => $couponCode,
            ]);

        // Assert that everything went smoothly.
        $response->assertRedirect(route('home'));
    }
}