Wanted but not invoked: Mockito and Retrofit - unit-testing

Question

I'm trying to unit test a call to my api using Mockito.
I took a look at all the issues already mentioned here on S.O together with the solutions, but so far, none of them have been conclusive.
MyService is an interface which holds several resources. Here's a sample:
public interface MyService {
#GET("/myresource")
Call<MyResponse> getDataFromServer();
}
Inside my Application class, I have a static class which returns an instance of MyService
public static MyService getApiService() {
return mApiService;
}
So, from there on inside one of my classes, I make the call to the web service:
Call<MyResponse> call = getApiService.getDataFromServer();
call.enqueue(myCallback)
The rest follows with the callback method being called....
Here's my test class:
#RunWith(AndroidJUnit4.class)
public class SampleTest {
#Mock
private MyService mService;
#Captor
private ArgumentCaptor<Callback<MyResponse>> callbackArgumentCaptor;
#Mock
private Call<MyResponse> mockCall;
// Rule to trigger the creation of #Mock annotated objects.
#Rule
public MockitoRule mockitoRule = MockitoJUnit.rule();
#Test
public void testDoAction() throws NullInsteadOfMockException {
when(mService.doSomeAction()).thenReturn(mockCall);
mService.doSomeAction();
verify(mockCall).enqueue(callbackArgumentCaptor.capture());
}
}
Here's the error I have once I run the test:
Wanted but not invoked:
mockCall.enqueue(
<Capturing argument>
);
Actually, there were zero interactions with this mock.
I have the same error even if use MockitoJunitRunner (in place of AndroidJunitRunner) and initialize my mock objects inside a setup method I define like this:
#Before
public void setUp() throws Exception{
MockitoAnnotations.initMocks(this);
}
Mockito version : 2.7.19
I want to be able to test the API response, so I mocked the API service, defined a captor for the retrofit Callback

Answer 1

It's a bit strange what you're trying to do here. You're testing a class, but you mock it. You should test the real class - MyService. I assume that your service looks a bit like:
public class MyService {
private final Call<MyResponse> call;
public MyService(Call<MyResponse> call) {
this.call = call;
}
public void doSomeAction() {
call.enqueue(...);
}
}
Ideally you should have something like:
#RunWith(AndroidJUnit4.class)
public class SampleTest {
private MyService mService;
#Captor
private ArgumentCaptor<Callback<MyResponse>> callbackArgumentCaptor;
#Mock
private Call<MyResponse> mockCall;
#Rule
public MockitoRule mockitoRule = MockitoJUnit.rule();
#Before
public void setUp() throws Exception{
MockitoAnnotations.initMocks(this);
mService = new MyService(mockCall);
}
#Test
public void testDoAction() throws NullInsteadOfMockException {
mService.doSomeAction();
verify(mockCall).enqueue(callbackArgumentCaptor.capture());
}
}
So the idea is to mock all the dependencies of the class you're unit testing and pass them to the class somehow. Here I'm injecting them in the constructor. I don't know if this is the case for you, but a setter or a field works too.
Then the test simply calls the real method in the service class and if this method is suppose to enqueue the call, then the verify should pass.
The reason it doesn't work in your case is because you're mocking the service so when you call mService.doSomeAction() this doesn't call your implementation, which I suppose should call enqueue. This is why the verify fails. In other words, it's true that enqueue is never called on the call object.