Testing and Mocking external Services¶

Introduction / Context¶

An important typical work in a Flamingo application is to consume external services - often via Restful APIs.

Flamingo acts then as a Consumer of Services provided by a Provider

During development and also in certain test steps - you usually want to fake or mock this external services.

So lets clarify the naming:

Faking: Means instead of calling the actual API we are faking a result internally, e.g. by using an implementation that dont calls an API but just answers with (fixed) faked results.
Mocking: Means we try to use the real code that later (in production) should call the real service. But instead of using the real external service we call a separate mock. This mock needs to run.

Faking is easy and also allows for local independent testing. Mocking has the advantage to test your application in a more production-like setup.

Contract Testing¶

If you use a Mock, then someone should verify that the Mock behaves like the real service (or the other way around). This is what is called contract testing. You should establish this.

Consumer Based Contract Testing¶

In case you have control over the provider you can use consumer based contract testing. That means that a contract test provided by Flamingo is executed in the build pipeline of the provider.

We support pact for this.

Faking in Flamingo¶

The Ports and Adapters concept allows to register a "fake" implementation.

Adding the fake implementation:

###PROJECT###
└───fakeservices
    └─── servicepackagename
    │    └─── service.go
    module.go

In module.go, register the fake implementation:

injector.Override(new(productdomain.BrandService), "").To(product.FakeService{})

Better is to make this even configurable. And then add feature flags to your configuration in dev context (context_dev.yml). This way you automatically use the fake implementation when starting Flamingo in with CONTEXT=dev.

Testing and Mocking external Services¶

Introduction / Context¶

Contract Testing¶

Consumer Based Contract Testing¶

Faking in Flamingo¶

Mocking in Flamingo¶

Getting started with Pact¶