How to use createResume method of org.mockitousage.PlaygroundTest class

I've finally been able to solve my problem. The key to the answer is the line

java.lang.IllegalStateException: Could not self-attach to current VM using external process

For Java 9 and more, one must add -Djdk.attach.allowAttachSelf=true as VM argument to avoid this exception. When I did, unit tests ran perfectly.

Here are the links where I've found this :

https://github.com/raphw/byte-buddy/issues/612

https://github.com/mockk/mockk/issues/254

There are different ways to use Mockito - I'll go through them one by one.

Manually

Creating mocks manually with Mockito::mock works regardless of the JUnit version (or test framework for that matter).

Annotation Based

Using the @Mock-annotation and the corresponding call to MockitoAnnotations::initMocks to create mocks works regardless of the JUnit version (or test framework for that matter but Java 9 could interfere here, depending on whether the test code ends up in a module or not).

Mockito Extension

JUnit 5 has a powerful extension model and Mockito recently published one under the group / artifact ID org.mockito : mockito-junit-jupiter.

You can apply the extension by adding @ExtendWith(MockitoExtension.class) to the test class and annotating mocked fields with @Mock. From MockitoExtension's JavaDoc:

@ExtendWith(MockitoExtension.class)
public class ExampleTest {

    @Mock
    private List list;

    @Test
    public void shouldDoSomething() {
        list.add(100);
    }

}

The MockitoExtension documentation describes other ways to instantiate mocks, for example with constructor injection (if you rpefer final fields in test classes).

No Rules, No Runners

JUnit 4 rules and runners don't work in JUnit 5, so the MockitoRule and the Mockito runner can not be used.

From the Mockito documentation :

Resetting mocks (Since 1.8.0)

Smart Mockito users hardly use this feature because they know it could be a sign of poor tests. Normally, you don't need to reset your mocks, just create new mocks for each test method. Instead of reset() please consider writing simple, small and focused test methods over lengthy, over-specified tests. First potential code smell is reset() in the middle of the test method. This probably means you're testing too much. Follow the whisper of your test methods: "Please keep us small & focused on single behavior". There are several threads about it on mockito mailing list.

The only reason we added reset() method is to make it possible to work with container-injected mocks.

You should probably just recreate the spy in a @BeforeMethod :

public class Program {

    private TestObject testObject = new TestObject();
    private TestObject spyTestObject;

    @BeforeMethod
    public void buildSpy() {
        spyTestObject = spy(testObject);
    }

    @Test
    public void test1() {
       spyTestObject.makeSth(); 
       verify(spyTestObject , only()).someMethodNeedToBeChecked(); 
    }

    @Test
    public void test2() {
        // Some different scenario
       spyTestObject.makeSth(); 
       verify(spyTestObject , only()).someMethodNeedToBeChecked(); 
        ...
    }
}

I don't quite follow what problem you're having using Mockito. Assuming you create a mock of the interface that contains your myMethod() method, you can then verify only the parameters to the method that you are interested in. For example (assuming the interface is called MyInterface and using JUnit 4):

@Test
public void test() {
    MyInterface myInterface = mock(MyInterface.class);
    FooBar expectedFooBar = new FooBar();        

    // other testing stuff

    verify(myInterface).myMethod(any(), any(), eq(expectedFooBar), any(), ...);
}

You'll need to do a static import on the Mockito methods for this to work. The any() matcher doesn't care what value has been passed when verifying.

You can't avoid passing something for every argument in your method (even if it's only NULL).

Mockito itself doesn't seem to be able to mock native methods according to this Google Group thread. However you do have two options:

1. Wrap the TableElement class in an interface and mock that interface to properly test that your SUT calls the wrapped insertRow(...) method. The drawback is the extra interface that you need to add (when GWT project should've done this in their own API) and the overhead to use it. The code for the interface and the concrete implementation would look like this:

   // the mockable interface
   public interface ITableElementWrapper {
       public void insertRow(int index);
   }
   
   // the concrete implementation that you'll be using
   public class TableElementWrapper implements ITableElementWrapper {
       TableElement wrapped;
   
       public TableElementWrapper(TableElement te) {
           this.wrapped = te;
       }
   
       public void insertRow(int index) {
           wrapped.insertRow(index);
       }
   }
   
   // the factory that your SUT should be injected with and be 
   // using to wrap the table element with
   public interface IGwtWrapperFactory {
       public ITableElementWrapper wrap(TableElement te);
   }
   
   public class GwtWrapperFactory implements IGwtWrapperFactory {
       public ITableElementWrapper wrap(TableElement te) {
           return new TableElementWrapper(te);
       }
   }
   

2. Use Powermock and it's Mockito API extension called PowerMockito to mock the native method. The drawback is that you have another dependency to load into your test project (I'm aware this may be a problem with some organizations where a 3rd party library has to be audited first in order to be used).

Personally I'd go with option 2, as GWT project is not likely to wrap their own classes in interfaces (and it is more likely they have more native methods that needs to be mocked) and doing it for yourself to only wrap a native method call is just waste of your time.

It sounds like you need MockSettings.extraInterfaces.

MockedClass mockedClass = mock(MockedClass.class,
    withSettings().extraInterfaces(SampleInterface.class));

Note that it comes with its own warning label:

This mysterious feature should be used very occasionally. The object under test should know exactly its collaborators & dependencies. If you happen to use it often than [sic] please make sure you are really producing simple, clean & readable code.

As an alternative, create an interface for testing that extends all of the interfaces you want your mock to implement, and mock that the usual way.

public abstract class ForTest implements SampleInterface {}

MockedClass mockedClass = mock(ForTest.class);

it is because of the version conflict between PowerMockito and Mockito artifacts. "MockCreationSettings.isUsingConstructor" method is removed in new versions, so you need to be sure you are using correct versions. e.g use PowerMockito version 1.6.2 with Mockito version 1.10.19 (this version has that missing method)

I think you do need to cast it, but it shouldn't be too bad:

Foo<Bar> mockFoo = (Foo<Bar>) mock(Foo.class);
when(mockFoo.getValue()).thenReturn(new Bar());

Note that documentToPojo takes a Class as its second argument. any(Foo.class) returns an argument of type Foo, not of type Class<Foo>, whereas eq(WorkItemDTO.class) should return a Class<WorkItemDTO> as expected. I'd do it this way:

when(mongoUtil.documentToPojo(
    Mockito.any(Document.class),
    Mockito.eq(WorkItemDTO.class))).thenReturn(...);