How to use MockitoClearTest class of org.mockito package

The necessary method is Mockito#verify:

public static <T> T verify(T mock,
                           VerificationMode mode)

mock is your mocked object and mode is the VerificationMode that describes how the mock should be verified. Possible modes are:

verify(mock, times(5)).someMethod("was called five times");
verify(mock, never()).someMethod("was never called");
verify(mock, atLeastOnce()).someMethod("was called at least once");
verify(mock, atLeast(2)).someMethod("was called at least twice");
verify(mock, atMost(3)).someMethod("was called at most 3 times");
verify(mock, atLeast(0)).someMethod("was called any number of times"); // useful with captors
verify(mock, only()).someMethod("no other method has been called on the mock");

You'll need these static imports from the Mockito class in order to use the verify method and these verification modes:

import static org.mockito.Mockito.atLeast;
import static org.mockito.Mockito.atLeastOnce;
import static org.mockito.Mockito.atMost;
import static org.mockito.Mockito.never;
import static org.mockito.Mockito.only;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;

So in your case the correct syntax will be:

Mockito.verify(mock, times(4)).send()

This verifies that the method send was called 4 times on the mocked object. It will fail if it was called less or more than 4 times.

If you just want to check, if the method has been called once, then you don't need to pass a VerificationMode. A simple

verify(mock).someMethod("was called once");

would be enough. It internally uses verify(mock, times(1)).someMethod("was called once");.

It is possible to have multiple verification calls on the same mock to achieve a "between" verification. Mockito doesn't support something like this verify(mock, between(4,6)).someMethod("was called between 4 and 6 times");, but we can write

verify(mock, atLeast(4)).someMethod("was called at least four times ...");
verify(mock, atMost(6)).someMethod("... and not more than six times");

instead, to get the same behaviour. The bounds are included, so the test case is green when the method was called 4, 5 or 6 times.

What you are asking is not possible because your legacy code relies on a static method getInstance() and Mockito does not allow to mock static methods, so the following line won't work

when(FormatterService.getInstance()).thenReturn(formatter);

There are 2 ways around this problem:

1. Use a different mocking tool, such as PowerMock, that allows to mock static methods.

2. Refactor your code, so that you don't rely on the static method. The least invasive way I can think of to achieve this is by adding a constructor to DriverSnapshotHandler that injects a FormatterService dependency. This constructor will be only used in tests and you production code will continue to use the real singleton instance.

   public static class DriverSnapshotHandler {
   
       private final FormatterService formatter;
   
       //used in production code
       public DriverSnapshotHandler() {
           this(FormatterService.getInstance());
       }
   
       //used for tests
       DriverSnapshotHandler(FormatterService formatter) {
           this.formatter = formatter;
       }
   
       public String getImageURL() {
           return formatter.formatTachoIcon();
       }
   }
   

Then, your test should look like this :

FormatterService formatter = mock(FormatterService.class);
when(formatter.formatTachoIcon()).thenReturn("MockedURL");
DriverSnapshotHandler handler = new DriverSnapshotHandler(formatter);
handler.getImageURL();
verify(formatter, atLeastOnce()).formatTachoIcon();

The reason why IsNonEmpty.matches() gets called on the second line of stubbing is that the Mockito.argThat(new IsEmpty()) returns null, which is then passed to mockHTable.get(). This call has to be checked against the earlier stubbing, to see whether it's a match; and that means calling IsNonEmpty.matches().

I'm not sure why this makes your test fail - it's hard to tell without seeing all of the code.

But, I would seriously recommend using doReturn...when instead of when...thenReturn whenever you have to stub the same mock more than once. You won't encounter issues like this if you do. In fact, I prefer to use doReturn...when in preference to when...thenReturn always (and similarly doThrow and doAnswer), although most people prefer when...thenReturn.

Re-writing one of your stubbing lines with the doReturn...when syntax looks like the following. The other is similar.

Mockito.doReturn(dbResult).when(mockHTable).get(Mockito.argThat(new IsNonEmpty()));  

Lastly, a plea, on behalf of the Mockito development team (of which I am a member). If you think there is a bug in Mockito here - and from your description, I think there may well be - please EITHER

• send a message to the Mockito mailing group (mockito@googlegroups.com) OR
• raise an issue on the Mockito issues list (http://code.google.com/p/mockito/issues/list).

It's useful to the Mockito team if you can actually post a complete example, rather than just what you think the key lines are - sometimes the cause of a Mockito problem is in quite an unexpected place.

Here you want to test EventMonitor.doStuff(param) and while executing this method you want to make it sure whether the correct methods on IEventListener were invoked or not.

So, in order to test doStuff(param), you don't need to have a real implementation of IEventListener: what you need is just a mock implementation of IEventListener and you have to verify the exact number of method invocations on IEventListener while testing doStuff. This can be achieved with Mockito or any other mocking framework.

Here is an example with Mockito:

import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;

import org.junit.Before;
import org.junit.Test;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;

public class EventMonitorTest {

    //This will create a mock of IEventListener
    @Mock
    IEventListener eventListener;

    //This will inject the "eventListener" mock into your "EventMonitor" instance.
    @InjectMocks
    EventMonitor eventMonitor = new EventMonitor();

    @Before
    public void initMocks() {
        //This will initialize the annotated mocks
        MockitoAnnotations.initMocks(this);
    }

    @Test
    public void test() {
        eventMonitor.doStuff(param);
        //Here you can verify whether the methods "doStuff1" and "doStuff2" 
        //were executed while calling "eventMonitor.doStuff". 
        //With "times()" method, you can even verify how many times 
        //a particular method was invoked.
        verify(eventListener, times(1)).doStuff1();
        verify(eventListener, times(0)).doStuff2();
    }

}

I'll leave this here for future reference and to be able to elaborate a bit more, even though I've answered in the comments.

What you're trying to accomplish is to put the stream in the onError flow. Unfortunately, by mocking it like this:

Mockito.`when`(apiManager.getPlacesPagedObservable(
                   Mockito.anyString(), Mockito.anyInt()))
                           .thenThrow(Exception(EXCEPTION_MESSAGE1))

You're actually telling Mockito to setup your mock in a way that just calling apiManager.getPlacesPagedObservable(anystring, anystring) should thrown an exception.

It is indeed true that throwing an exception inside an Rx stream will cause the entire stream to stop and end up in the onError method. However, this is exactly the problem with the approach you're using. You're not inside the stream when the exception is thrown.

Instead what you want to do is tell Mockito that once you call apiManager.getPlacesPagedObservable(anystring, anystring) you want to return a stream that will end up in the onError. This can be easily achieved with Observable.error() like so:

Mockito.`when`(apiManager.getPlacesPagedObservable(
               Mockito.a‌​nyString(), Mockito.anyInt()))
                    .thenReturn(Observable.error(
                                Exception(EXCEPTION_MESSAGE1)))

(It might be possible that you need to add some type information in this part here Observable.error(), you might also need to use something else instead of an observable - single, completable, etc.)

The mocking above will tell Mockito to setup your mock to return an observable that will error as soon as it's subscribed to. This will in turn put your subscriber directly in the onError stream with the specified exception.

Let me begin by saying you are on the right track by using Constructor Injection and not Field Injection(which makes writing tests with mocks much simpler).

public class MyServiceImplTest 
{
    private MyDataService myDataService;
    private NyService myService;

    @Mock
    private MyRepository myRepository;

    @Before
    public void setUp() {
        MockitoAnnotations.initMocks(this); // this is needed for inititalizytion of mocks, if you use @Mock 
        myDataService = new MyDataServiceImpl(myRepository);
        myService = new MyServiceImpl(myDataService);
    }

    @Test
    public void getById_ValidId() {

        doReturn(someMockData).when(myRepository).findOne("1");
        MyObject myObject = myService.getById("1");

        //Whatever asserts need to be done on the object myObject 
    }
}

The call goes all the way from your service --> dataService. But only your repository calls are mocked.
This way you can control and test all the other parts of your classes(both service and dataService) and mock only repository calls.

See Update below: You don't need a Factory

If you are using Jersey 2, one solution would be to use Custom Injection and Lifecycle Management feature (with HK2 - which comes with the Jersey dist). Also required would be a Mocking framework of course. I'm going to use Mockito.

First create a Factory with mocked instance:

public static interface GreetingService {
    public String getGreeting(String name);
}

public static class MockGreetingServiceFactory 
                                     implements Factory<GreetingService> {
    @Override
    public GreetingService provide() {
        final GreetingService mockedService
                = Mockito.mock(GreetingService.class);
        Mockito.when(mockedService.getGreeting(Mockito.anyString()))
                .thenAnswer(new Answer<String>() {
                    @Override
                    public String answer(InvocationOnMock invocation) 
                                                      throws Throwable {
                        String name = (String)invocation.getArguments()[0];
                        return "Hello " + name;
                    }

                });
        return mockedService;
    }

    @Override
    public void dispose(GreetingService t) {}
}

Then use the AbstractBinder to bind the factory to the interface/service class, and register the binder. (It's all described in the link above):

@Override
public Application configure() {
    AbstractBinder binder = new AbstractBinder() {
        @Override
        protected void configure() {
            bindFactory(MockGreetingServiceFactory.class)
                               .to(GreetingService.class);
        }
    };
    ResourceConfig config = new ResourceConfig(GreetingResource.class);
    config.register(binder);
    return config;
}

Seems like a lot, but it's just an option. I'm not too familiar with the test framework, or if it has an mocking capabilities for injection.

Here is the full test:

import javax.inject.Inject;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.client.Client;
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.core.Application;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import org.glassfish.hk2.api.Factory;
import org.glassfish.hk2.utilities.binding.AbstractBinder;
import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.test.JerseyTest;
import org.junit.Assert;
import org.junit.Test;
import org.mockito.Mockito;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;

public class ServiceMockingTest extends JerseyTest {

    @Path("/greeting")
    public static class GreetingResource {

        @Inject
        private GreetingService greetingService;

        @GET
        @Produces(MediaType.TEXT_PLAIN)
        public String getGreeting(@QueryParam("name") String name) {
            return greetingService.getGreeting(name);
        }
    }

    public static interface GreetingService {
        public String getGreeting(String name);
    }
    
    public static class MockGreetingServiceFactory 
                                  implements Factory<GreetingService> {
        @Override
        public GreetingService provide() {
            final GreetingService mockedService
                    = Mockito.mock(GreetingService.class);
            Mockito.when(mockedService.getGreeting(Mockito.anyString()))
                    .thenAnswer(new Answer<String>() {
                        @Override
                        public String answer(InvocationOnMock invocation) 
                                                       throws Throwable {
                            String name = (String)invocation.getArguments()[0];
                            return "Hello " + name;
                        }

                    });
            return mockedService;
        }

        @Override
        public void dispose(GreetingService t) {}
    }

    @Override
    public Application configure() {
        AbstractBinder binder = new AbstractBinder() {
            @Override
            protected void configure() {
                bindFactory(MockGreetingServiceFactory.class)
                        .to(GreetingService.class);
            }
        };
        ResourceConfig config = new ResourceConfig(GreetingResource.class);
        config.register(binder);
        return config;
    }
    
    @Test
    public void testMockedGreetingService() {
        Client client = ClientBuilder.newClient();
        Response response = client.target("http://localhost:9998/greeting")
                .queryParam("name", "peeskillet")
                .request(MediaType.TEXT_PLAIN).get();
        Assert.assertEquals(200, response.getStatus());
        
        String msg = response.readEntity(String.class);
        Assert.assertEquals("Hello peeskillet", msg);
        System.out.println("Message: " + msg);
        
        response.close();
        client.close();
       
    }
}

Dependencies for this test:

<dependency>
    <groupId>org.glassfish.jersey.test-framework.providers</groupId>
    <artifactId>jersey-test-framework-provider-grizzly2</artifactId>
    <version>2.13</version>
</dependency>
<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-all</artifactId>
    <version>1.9.0</version>
</dependency>

UPDATE

So in most cases, you really don't need a Factory. You can simply bind the mock instance with its contract:

@Mock
private Service service;

@Override
public ResourceConfig configure() {
    MockitoAnnotations.initMocks(this);
    return new ResourceConfig()
        .register(MyResource.class)
        .register(new AbstractBinder() {
            @Override
            protected configure() {
                bind(service).to(Service.class);
            }
        });
}

@Test
public void test() {
    when(service.getSomething()).thenReturn("Something");
    // test
}

Much simpler!

I changed TestCompile to androidTestCompile and it's worked without problems.

testCompile 'junit:junit:4.12'

to

androidTestCompile 'junit:junit:4.12'

Mockito 2 now supports final classes and methods!

But for now that's an "incubating" feature. It requires some steps to activate it which are described in What's New in Mockito 2:

Mocking of final classes and methods is an incubating, opt-in feature. It uses a combination of Java agent instrumentation and subclassing in order to enable mockability of these types. As this works differently to our current mechanism and this one has different limitations and as we want to gather experience and user feedback, this feature had to be explicitly activated to be available ; it can be done via the mockito extension mechanism by creating the file src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker containing a single line:

mock-maker-inline

After you created this file, Mockito will automatically use this new engine and one can do :

 final class FinalClass {
   final String finalMethod() { return "something"; }
 }

 FinalClass concrete = new FinalClass(); 

 FinalClass mock = mock(FinalClass.class);
 given(mock.finalMethod()).willReturn("not anymore");

 assertThat(mock.finalMethod()).isNotEqualTo(concrete.finalMethod());

In subsequent milestones, the team will bring a programmatic way of using this feature. We will identify and provide support for all unmockable scenarios. Stay tuned and please let us know what you think of this feature!