How to use callMethodOnMock method of org.mockitousage.stacktrace.PointingStackTraceToActualInvocationTest class

I got this exception even though I had a public method annotaded with @Test. Turned out was importing org.junit.jupiter.api.Test, I changed to org.junit.Test and it worked fine.

If your build script contains something like this:

testOptions {
    unitTests.returnDefaultValues = true
}

then it's a cause why your test doesn't fail even if your don't specify a mock for Bundle class.

There are a few options to deal with this problem:

1. Use Mockito mocking framework to mock a Bundle class. Unfortunately, you have to write a lot of boilerplate code by yourself. For example you can use this method to mock a bundle object, so it will return you the right values by getString method:

    @NonNull
    private Bundle mockBundle() {
          final Map<String, String> fakeBundle = new HashMap<>();
          Bundle bundle = mock(Bundle.class);
          doAnswer(new Answer() {
          @Override
          public Object answer(InvocationOnMock invocation) throws Throwable {
                Object[] arguments = invocation.getArguments();
                String key = ((String) arguments[0]);
                String value = ((String) arguments[1]);
                fakeBundle.put(key, value);
                return null;
          }
          }).when(bundle).putString(anyString(), anyString());
          when(bundle.get(anyString())).thenAnswer(new Answer<String>() {
                 @Override
                 public String answer(InvocationOnMock invocation) throws Throwable {
                      Object[] arguments = invocation.getArguments();
                      String key = ((String) arguments[0]);
                      return fakeBundle.get(key);
                  }
          });
          return bundle;
     }
   

2. Use Robolectric framework that provides some kind of shadow classes for your unit tests. This allows you to use Android specific classes in unit testing and they will act properly. By using that framework your unit test will act properly almost without any changes from your side.

3. The most undesirable by you, I guess, but well, it's eligible. You can make your test functional and run it on your android device or emulator. I do not recommend that way because of speed. Before executing tests you have to build a test apk, install it and run. This is super slow if you're going to do TDD.

O.K, I got my mistake!!! I've used the @InjectMocks but initialized the same variable in the init() method... So what happened was that mockito injected the mock objects to my variable - but seconds later I ran it over - initializing that very same variable!!!

Mockito provides regex matcher in standard org.mockito.Matchers class. Here is an example how this function can be used to verify invocation with proper parameter value:

verify(restMock, times(1)).exchange(matches(".*text=welcome.*to.*blah"), eq(HttpMethod.GET), any(ResponseEntity.class), eq(String.class));

Since Mockito 1.9.5+ and Java 8+

You can use a lambda expression, like:

when(myMock.myFunction(anyString())).thenAnswer(i -> i.getArguments()[0]);

Where i is an instance of InvocationOnMock.

For older versions

You can create an Answer in Mockito. Let's assume, we have an interface named MyInterface with a method myFunction.

public interface MyInterface {
    public String myFunction(String abc);
}

Here is the test method with a Mockito answer:

public void testMyFunction() throws Exception {
    MyInterface mock = mock(MyInterface.class);
    when(mock.myFunction(anyString())).thenAnswer(new Answer<String>() {
    @Override
    public String answer(InvocationOnMock invocation) throws Throwable {
        Object[] args = invocation.getArguments();
        return (String) args[0];
    }
    });

    assertEquals("someString",mock.myFunction("someString"));
    assertEquals("anotherString",mock.myFunction("anotherString"));
}

I found the faulty part.

I changed

@RunWith(MockitoJUnitRunner.class)

to

@RunWith(PowerMockRunner.class)

Now the mocking works. But i have to say that as Jon Skeet printed out, the enum does not have everywhere that mocked member-instance. So in another Unit test calling MyEnum.CONSTANT.sayHello(); will print again it works instead of Hello!.

After a lot more hunting around and looking at all the options Mockito/Powermock had to offer, I found the solution (which I will share in case others run into this same issue).

When you have private member variables that are never initialized (and just assumed created in other places), you can use the @InjectMocks annotation to "inject" Mocks you want into your class you are testing.

1. Add a variable in your test class for the class you are testing, and give it the annotation @InjectMocks (org.Mockito.InjectMocks).
2. Use @Mock annotations to setup the mocks you want to inject. Use the @Mock (name = "privateVariableNameHere") name property to map the Mock object to the private variable inside your class you are testing.
3. In either a setup function or before you call your class, initialize the mocks. The easiest way I have found is to use a "setup" method with the @Before annotation. Then inside there call MockitoAnnotations.initMocks(this); to quickly initialize anything with the @Mock annotation.
4. Define your Mock functionality in your test method (before calling the method you are testing).
5. Using the @InjectMock object, call your method you are testing... the mocks SHOULD be hooked in and working as defined in the earlier steps.

So for the example class I use above, the code to test/mock would have Connection returned as a mock which you can do whatever with. Based on the example above in my question, this is what the code would look like:

@RunWith(PowerMockRunner.class)
@PrepareForTest({/* Static Classes I am Mocking */})
public class ExampleTest {
  @Mock (name = "queueFactory") //same name as private var.
  QueueConnectionFactory queueFactoryMock;
  @Mock
  Connection connectionMock; //the object we want returned
  @InjectMocks
  Example exampleTester; //the class to test

  @Before
  public void setup(){
    MockitoAnnotations.initMocks(this); // initialize all the @Mock objects
    // Setup other Static Mocks
  }

  @Test
  public void testTestMe(){
    //Mock your objects like other "normally" mocked objects
    PowerMockito.when(queueFactoryMock.createConnection()).thenReturn(connectionMock);
    //...Mock ConnectionMock functionality...
    exampleTester.testMe();
  }
}

Try View -> Tool Windows -> Maven projects, then click the blue icon in the top left of the tool window (Reimport all Maven projects). You should be able to find the dependencies in the project view, under external libraries.

If this does not work, there is probably something wrong with your maven config (pom.xml). Try mvn clean install from the command line see if it gives any errors.

This would be hard to test because it loops. One solution would be to break out this.client.newCall(request).execute() into a separate function sendRequest(Request request, int attemptsRemaining). Then you could use a spy that stubs that method to return different responses depending on the number of attempts remaining.
The nice thing I realized about okhttp is that you can just build a fake response yourself. For example,

Request mockRequest = new Request.Builder()
                .url("https://some-url.com")
                .build();
return new Response.Builder()
                .request(mockRequest)
                .protocol(Protocol.HTTP_2)
                .code(401) // status code
                .message("")
                .body(ResponseBody.create(
                        MediaType.get("application/json; charset=utf-8"),
                        "{}"
                ))
                .build();

So you can create and stub a simple method that returns a response, and you're basically good to go for testing.