How to use DetachedThreadLocal class of org.mockito.internal.util.concurrent package

Mockito.verify(foo, Mockito.times(1)).add("1");
Mockito.verify(foo, Mockito.times(1)).add(Mockito.anyString());

The first verify checks the expected parametrized call and the second verify checks that there was only one call to add at all.

While a partial mock isn't a bad idea, you might find your code easier to follow if you use an ArgumentCaptor instead to get the values after the fact. It's a special argument matcher that keeps track of the value it matches.

// initialized with MockitoAnnotations.initMocks();
@Captor ArgumentCaptor<Integer> offsetCaptor;
@Captor ArgumentCaptor<float[]> floatsCaptor;
@Mock Bar bar;

@Test
public void valuesShouldBeCloseEnough() {
  Sut sut = new Sut(bar);
  sut.doSomething();
  verify(bar).setFoo(offsetCaptor.capture(), floatsCaptor.capture());

  // check values with assertValuesAreCloseEnough, declared elsewhere
  assertValuesAreCloseEnough(offsetCaptor.getValue(), floatsCaptor.getValue());
}

If you use Mockito you can use verify() to check the number of times a method was called. Use it like this:

verify(mockedObject, times(1)).methodToValidate();

You can check if methodToValidate() was called with a specific string, e.i verify(mockedObject, times(1)).methodToValidate("a specific value"); or you can use it with anyString() like this: verify(mockedObject, times(1)).methodToValidate(anyString());.

Unless this method is called with your specified paramterer, the test will fail

Read more about verify here.

UPDATE

Since your edited post states that you are using jMock, a quick googeling showed me that it is possible to achieve a similar behaviour with jMock and it's expect method. It's used as below:

mockedObject.expects(once()).method("nameOfMethod").with( eq("An optional paramter") );

More detailed explanation can be found by reading jMocks getting started page.

Caused by: org.mockito.exceptions.base.MockitoException: Checked exception is invalid for this method! Invalid: java.net.ConnectException: Test exception

As stated by the exception message (and told in comments), you have to throw a RestClientException, not a ConnectException:

Mockito.when(restOperations.exchange(
        Mockito.anyString(), Mockito.<HttpMethod>any(), Mockito.<HttpEntity<?>>any(),
        Mockito.<Class<UserByRoleHolder>>any())).thenThrow(new RestClientException("Test exception"));

You get this error message, because the method exchange declares no thrown exception and ConnectException is a checked exception (i.e. must be declared when thrown).

This question is ancient, but Mockito v2.1.0+ now has a built-in feature for this.

verify(mock, description("This will print on failure")).someMethod("some arg");

More examples included from @Lambart's comment below:

verify(mock, times(10).description("This will print if the method isn't called 10 times")).someMethod("some arg");
verify(mock, never().description("This will print if someMethod is ever called")).someMethod("some arg");
verify(mock, atLeastOnce().description("This will print if someMethod is never called with any argument")).someMethod(anyString());

As for me the easiest way it's just to save the link to the read object when you initialize your Spy object:

Foo realFoo = new Foo();
Foo spyFoo = Mockito.spy(realFoo);

Now you can stub it like this:

doAnswer(invocation -> realFoo.getSome() + "spyMethod").when(spyFoo).getSome();

One more way is to call invocation.callRealMethod():

doAnswer(invocation -> invocation.callRealMethod() + "spyMethod").when(spyFoo).getSome();

But in this case you may need to cast the return value as long as invocation.callRealMethod() returns Object.

First Mock your Worker with Mockito (just as you did). Also mock your ChildService. Then:

@Test
public void shouldUseChildService() {
  ArgumentCaptor<Callable> callableCaptor = ArgumentCaptor.forClass(Callable.class);
  ArgumentCaptor<Consumer> consumerCaptor = ArgumentCaptor.forClass(Consumer.class);

  parentService.doAction();

  verify(worker).execute(callableCaptor.capture(), consumerCaptor.capture());
  callableCaptor.getValue().call(); //this will execute whatever was captured
  consumerCaptor.getValue().accept(null);//this will execute whatever was captured

  // now verify that childService::listClients and childService::refreshObjects have been called
}

You need create real A class because you want to test it but you need to mock other classes used in A class. Also, you can find mockito documentation says that don't mock everything.

class ATest {
        @Mock
        private B b;
        private A a;
        @Before
        public void init() {
            MockitoAnnotations.initMocks(this);
            a = new A(b);
        }
        @Test
        public String someMethodTest() {
            String result = "result";
            Mockito.when(b.execute()).thenReturn(result);
            String response = a.someMethod();
            Mockito.verify(b,  Mockito.atLeastOnce()).execute();
            assertEquals(response, result);
        }
    }

If your test cases are all in one class you could make use of a method annotated with @Before, e.g.:

...
private DAO mockDAO;

@Before 
public void setUp() {
    mockDAO = mock(DAO.class);
    when(mockDAO.a()).thenReturn("test");
    ...etc...
}    
...

Or, if you need the behaviour over many test classes you could write a utility class to set behaviour on a Mock instance, e.g.:

public class MockDAOPrototype {
    public DAO getMockWithDefaultBehaviour() {
        final DAO mockDAO = mock(DAO.class);
        when(mockDAO.a()).thenReturn("test");
        ...etc...

        return mockDAO;
    }
}

And then call MockDAOPrototype.getMockWithDefaultBehaviour() in your setUp method.