How to use Plugins.getMockMaker method of org.mockito.internal.util.MockUtil class

Mockito comes with a helper class to save you some reflection boiler plate code:

import org.mockito.internal.util.reflection.Whitebox;

//...

@Mock
private Person mockedPerson;
private Test underTest;

// ...

@Test
public void testMethod() {
    Whitebox.setInternalState(underTest, "person", mockedPerson);
    // ...
}

Update: Unfortunately the mockito team decided to remove the class in Mockito 2. So you are back to writing your own reflection boilerplate code, use another library (e.g. Apache Commons Lang), or simply pilfer the Whitebox class (it is MIT licensed).

Update 2: JUnit 5 comes with its own ReflectionSupport and AnnotationSupport classes that might be useful and save you from pulling in yet another library.

I think your results are compatible with the result that would happen if dbCollection is not a Mockito-mock (or your method is static or final). That would mean that a matcher is being used where none can be used; hence the "0 matchers expected, 1 recorded".

A Mock object is something used for unit testing. If you have an object whose methods you want to test, and those methods depend on some other object, you create a mock of the dependency rather than an actual instance of that dependency. This allows you to test your object in isolation.

Common Java frameworks for creating mock objects include JMock and EasyMock. They generally allow you to create mock objects whose behavior you can define, so you know exactly what to expect (as far as return values and side effects) when you call methods on the mock object.

As an example, one common use case might be in an MVC application, where you have a DAO layer (data access objects) and a Controller that performs business logic. If you'd like to unit test the controller, and the controller has a dependency on a DAO, you can make a mock of the DAO that will return dummy objects to your controller.

One thing thats important to note is that its usually the case that mock objects implement the same interface as the objects that they are mocking - this allows your code to deal with them via the interface type, as if they are instances of the real thing.

This will work. Using a spy calls the underlying method. Make sure value is initialized first.

    @Test
    public void testDoSmth() {
        ClassForTest testMock = spy(new ClassForTest());
        testMock.doSmth();
        verify(testMock, times(3)).prepareValue(anyString());
    }

    public class ClassForTest {
        private Integer value = 0;

        public void doSmth() {
            prepareValue("First call");
            prepareValue("Second call");
            prepareValue("Third call");
            System.out.println(value);
        }

        protected void prepareValue(String msg) {
            System.out.println("This is message: " + msg);
            value++;
        }
    }

You could also Stub Consecutive Calls (#10 in 2.8.9 api). In this case, you would use multiple thenReturn calls or one thenReturn call with multiple parameters (varargs).

import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

import org.junit.Before;
import org.junit.Test;

public class TestClass {

    private Foo mockFoo;

    @Before
    public void setup() {
        setupFoo();
    }

    @Test
    public void testFoo() {
        TestObject testObj = new TestObject(mockFoo);

        assertEquals(0, testObj.bar());
        assertEquals(1, testObj.bar());
        assertEquals(-1, testObj.bar());
        assertEquals(-1, testObj.bar());
    }

    private void setupFoo() {
        mockFoo = mock(Foo.class);

        when(mockFoo.someMethod())
            .thenReturn(0)
            .thenReturn(1)
            .thenReturn(-1); //any subsequent call will return -1

        // Or a bit shorter with varargs:
        when(mockFoo.someMethod())
            .thenReturn(0, 1, -1); //any subsequent call will return -1
    }
}

It is because of Java/Mockito compatibility. For example, if you are using Java 11 with Mockito 2.17.0, it will throw the same error (Upgrading to Mockito 2.22.0 or later will solve it). Aside from digging into their release artifact on Github, I am yet to see a comprehensive document that spells out the compatibility matrix. Here is a helpful compatibility Matrix (based on quick test)

• Mockito * - 2.17.0 => Java 8

(footnote: * - dont know how far back)

• Mockito 2.18.0 - 3.2.4 => Java 11

Since Mockito 2.x this has been replaced by implementations of org.mockito.listeners.MockitoListener which you engage like so:

Mockito.framework().addListener()

For example:

@Test
public void listAllMocks() {
    List<Object> mocks = new ArrayList<>();

    // can be replaced by a lambda if using java 8+
    Mockito.framework().addListener(new MockCreationListener() {
        @Override
        public void onMockCreated(Object mock, MockCreationSettings settings) {
            mocks.add(mock);
        }
    });

    A a = Mockito.mock(A.class);
    B b = Mockito.mock(B.class);

    // ... do something with a, b

    // verify
    assertThat(mocks.size(), is(2));
    assertThat(mocks, hasItem(a));
    assertThat(mocks, hasItem(b));
}

There's no way to use anyMapOf to do this. It's designed to help with the simple case of mapping simple classes to simple classes in Java 7, and yours is more complex than that.

Java 8 parameter inference improved, so in Java 8, you can just use any().

verify(dataProcessor).process(Matchers.any());

Barring that, the best way to make this look is either like you wrote above:

verify(dataProcessor).process(Matchers.<Map<String, Set<String>>>any());

Or by extracting the matcher to a static function, which gives Java just enough information it needs to infer the type on its own:

@Test public void yourTest() {
  // ...
  verify(dataProcessor).process(anyStringSetMap());
}

private static Map<String, Set<String>> anyStringSetMap() {
  return any();
}

(Caveat: Note that the return value of anyStringSetMap() is null; it's the side-effect of calling any that you're looking for. The extracted method is just to inform the Java compiler of the expected return type; beware that doing anything fancier will probably break in really-quite-interesting ways.)

It should be something like

@RunWith(SpringJUnit4ClassRunner.class)
public class aTest () {

    @Mock
    private B b;

    @Mock
    private C c;

    @Autowired
    @InjectMocks
    private A a;

}

If you want D to be Autowired dont need to do anything in your Test class. Your Autowired A should have correct instance of D. Also i think you need to use SpringJUnit4ClassRunner for Autowiring to work, with contextConfiguration set correctly. Because you are not using MockitoJunitRunner you need to initialize your mocks yourself using

MockitoAnnotations.initMocks(java.lang.Object testClass)