How to use should_stub method of org.mockitousage.customization.BDDMockitoTest class

That should be as simple as writing the following test class:

public class BarTest {
    @Test
    public void testFooIsInitializedProperly() throws Exception {
        // Arrange
        Bar bar = new Bar();

        // Act
        bar.initFoo();

        // Assert
        Foo foo = Whitebox.getInternalState(bar, "foo");
        assertThat(foo, is(notNull(Foo.class)));
    }
}

Adding the right (static) imports is left as an exercise to the reader :).

For these kinds of tests I like to use a little library called awaitility. You can do it yourself with a countdown latch, but as you have seen you have to hack up your test with a machete to make that work.

In this test you should call verify after you have awaited the latch.

Another problem in your code is the private Boolean response. Since you're changing it in another thread you should make that an AtomicBoolean or at least declare it volatile.

Take a look at the Mockito API docs. As the linked document mentions (Point # 12) you can use any of the doThrow(),doAnswer(),doNothing(),doReturn() family of methods from Mockito framework to mock void methods.

For example,

Mockito.doThrow(new Exception()).when(instance).methodName();

or if you want to combine it with follow-up behavior,

Mockito.doThrow(new Exception()).doNothing().when(instance).methodName();

Presuming that you are looking at mocking the setter setState(String s) in the class World below is the code uses doAnswer method to mock the setState.

World mockWorld = mock(World.class); 
doAnswer(new Answer<Void>() {
    public Void answer(InvocationOnMock invocation) {
      Object[] args = invocation.getArguments();
      System.out.println("called with arguments: " + Arrays.toString(args));
      return null;
    }
}).when(mockWorld).setState(anyString());

The point of Mockito (or any form of mocking, actually) isn't to mock the code you're checking, but to replace external dependencies with mocked code.

E.g., consider you have this trivial interface:

public interface ValueGenerator {
    int getValue();
}

And this is your code that uses it:

public class Incrementor {
    public int increment(ValueGenerator vg) {
        return vg.getValue() + 1;
    }
}

You want to test your Incrementor logic without depending on any specific implementation of ValueGenerator. That's where Mockito comes into play:

// Mock the dependencies:
ValueGenerator vgMock = Mockito.mock(ValueGenerator.class);
when(vgMock.getValue()).thenReturn(7);

// Test your code:
Incrementor inc = new Incrementor();
assertEquals(8, inc.increment(vgMock));

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".

Difference between a Spy and a Mock

When Mockito creates a mock – it does so from the Class of a Type, not from an actual instance. The mock simply creates a bare-bones shell instance of the Class, entirely instrumented to track interactions with it. On the other hand, the spy will wrap an existing instance. It will still behave in the same way as the normal instance – the only difference is that it will also be instrumented to track all the interactions with it.

In the following example – we create a mock of the ArrayList class:

@Test
public void whenCreateMock_thenCreated() {
    List mockedList = Mockito.mock(ArrayList.class);

    mockedList.add("one");
    Mockito.verify(mockedList).add("one");

    assertEquals(0, mockedList.size());
}

As you can see – adding an element into the mocked list doesn’t actually add anything – it just calls the method with no other side-effect. A spy on the other hand will behave differently – it will actually call the real implementation of the add method and add the element to the underlying list:

@Test
public void whenCreateSpy_thenCreate() {
    List spyList = Mockito.spy(new ArrayList());
    spyList.add("one");
    Mockito.verify(spyList).add("one");

    assertEquals(1, spyList.size());
}

Here we can surely say that the real internal method of the object was called because when you call the size() method you get the size as 1, but this size() method isn’t been mocked! So where does 1 come from? The internal real size() method is called as size() isn’t mocked (or stubbed) and hence we can say that the entry was added to the real object.

Source: http://www.baeldung.com/mockito-spy + self notes.

For void methods, I think you need to use the doThrow syntax.

So in your case it would be:

doThrow(BookingException.builder().build())
      .when(booking)
      .validate(any());

The source and target versions can be set separately for the compile and testCompile goals of the maven compiler plugin. You can change the settings either by defining properties in your pom:

<properties>
    <maven.compiler.source>1.4</maven.compiler.source>
    <maven.compiler.target>1.4</maven.compiler.target>
    <maven.compiler.testSource>1.5</maven.compiler.testSource>
    <maven.compiler.testTarget>1.5</maven.compiler.testTarget>
</properties>

Or by explicit configuration of the compiler plugin:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>2.4</version>
    <configuration>
        <source>1.4</source>
        <target>1.4</target>
        <testSource>1.5</testSource>
        <testTarget>1.5</testTarget>
    </configuration>
</plugin>

Mockito/Hamcrest and generic classes

Yes, this is a general problem with Mockito/Hamcrest. Generally using isA() with generic classes produces a warning.

There are predifined Mockito matchers for the most common generic classes: anyList(), anyMap(), anySet() and anyCollection().

Suggestions:

anyIterable() in Mockito 2.1.0

Mockito 2.1.0 added a new anyIterable() method for matching Iterables:

when(client.runTask(anyString(), anyString(), anyIterable()).thenReturn(...)

Ignore in Eclipse

If you just want to get rid of the warning in Eclipse. Option exists since Eclipse Indigo:

Window > Preferences > Java > Compiler > Errors/Warnings > Generic types > Ignore unavoidable generic type problems

Quick Fix with @SuppressWarnings

I suggest you do this if you have the problem only once. I personally don't remember ever needing an isA(Iterable.class).

As Daniel Pryden says, you can limit the @SuppressWarnings to a local variable or a helper method.

Use a generic isA() matcher with TypeToken

This solves the problem for good. But it has two disadvantages:

• The syntax is not too pretty and might confuse some people.
• You have an additional dependency on the library providing the TypeToken class. Here I used the TypeToken class from Guava. There's also a TypeToken class in Gson and a GenericType in JAX-RS.

Using the generic matcher:

import static com.arendvr.matchers.InstanceOfGeneric.isA;
import static org.mockito.ArgumentMatchers.argThat;

// ...

when(client.runTask(anyString(), anyString(), argThat(isA(new TypeToken<Iterable<Integer>>() {}))))
            .thenReturn(...);

Generic matcher class:

package com.arendvr.matchers;

import com.google.common.reflect.TypeToken;
import org.mockito.ArgumentMatcher;

public class InstanceOfGeneric<T> implements ArgumentMatcher<T> {
    private final TypeToken<T> typeToken;

    private InstanceOfGeneric(TypeToken<T> typeToken) {
        this.typeToken = typeToken;
    }

    public static <T> InstanceOfGeneric<T> isA(TypeToken<T> typeToken) {
        return new InstanceOfGeneric<>(typeToken);
    }

    @Override
    public boolean matches(Object item) {
        return item != null && typeToken.getRawType().isAssignableFrom(item.getClass());
    }
}