Retrofit - probably the most popular networking client in Android development. Basically it allows to create HTTP client in an interface - you just add annotation with HTTP method, relative or absolute path and proper request is constructed. Retrofit does not generate code in compile time - it creates implementations in runtime.
The method invocation:
Will create GET request to:
Now we will try to come up with a way to check if proper requests are constructed.
Basic test case
We will consider the following Retrofit interface with given configuration:
How could we actually perform some assertions on that? Was actually GET method used? Was search phrase included in query?
While we are using retrofit2.Call<T> we have Call.request() method available directly and we can perform assertions on Request object:
Test case with non-standard call adapter factory
In my opinion the power of Retrofit comes from call and converter adapter factories - instead of relying on built-in types (such as retrofit2.Call) you can add RxJava call adapter and framework would find a way to convert Call<T> into rx Single<T>. Unfortunately we won't have direct access to Call.request() method then!
To handle this case and have request to perform assertions on I came up with the following approach:
Use OkHttp MockWebServer to record incoming requests
Wrap system under test invocation with RemoteApi as lambda parameter and RecordedRequest as return type
Perform assertions on RecordedRequest
I highly encourage you to explore more methods and properties available in RecorderRequest - you may find there more things that may be useful in your test.
Now we have a way to perform assertions on request that was recorded in MockWebServer - with this approach we can design even more complex integration test suites.