How to use isClosed method of org.mockito.internal.MockedConstructionImpl class

Technically speaking both "mocks" and "spies" are a special kind of "test doubles".

Mockito is unfortunately making the distinction weird.

A mock in mockito is a normal mock in other mocking frameworks (allows you to stub invocations; that is, return specific values out of method calls).

A spy in mockito is a partial mock in other mocking frameworks (part of the object will be mocked and part will use real method invocations).

You are mocking the object that you're testing. That makes no sense. You should create a real WithDefinitions object and call its real method to test it. If you mock it, by definition, all its methods are replaced by mock implementations that do nothing.

Replace

WithDefinitions withDefinitions = Mockito.mock(WithDefinitions.class);

by something like

WithDefinitions withDefinitions = new WithDefinitions();

If possible I would try to write those test without Spring Context. If you create this class in your test without spring, then you have full control over its fields.

To set the @value field you can use Springs ReflectionTestUtils - it has a method setField to set private fields.

@see JavaDoc: ReflectionTestUtils.setField(java.lang.Object, java.lang.String, java.lang.Object)

If isSkipped() is not a final method, this problem probably indicates that you try to stub a method while stubbing of another method is in progress. It's not supported because Mockito relies on order of method invocations (when(), etc) in its stubbing API.

I guess you have something like this in your test method:

when(...).thenReturn(getSkippedBuild());

If so, you need to rewrite it as follows:

DynamicBuild build = getSkippedBuild();
when(...).thenReturn(build);

I had this issue and my problem was that I was calling my method with any() instead of anyInt(). So I had:

doAnswer(...).with(myMockObject).thisFuncTakesAnInt(any())

and I had to change it to:

doAnswer(...).with(myMockObject).thisFuncTakesAnInt(anyInt())

I have no idea why that produced a NullPointerException. Maybe this will help the next poor soul.

As you noted, these kind of tests are pointless (unless you're writing a unit test for Mockito itself, of course :-)).

The point of mocking is to eliminate external dependencies so you can unit-test your code without depending on other classes' code. For example, let's assume you have a class that uses the Employee class you described:

public class EmployeeExaminer {
    public boolean isJim(Employee e, int i) {
        return "Jim".equals(e.getName(i));
    }
}

And you'd like to write a unit test for it. Of course, you could use the actual Employee class, but then your test won't be a unit-test any more - it would depend on Employee's implementation. Here's where mocking comes in handy - it allows you to replace Employee with a predictable behavior so you could write a stable unit test:

// The object under test
EmployeeExaminer ee = new EmployeeExaminer();

// A mock Employee used for tests:
Employee emp = mock(Employee.class);
when(emp.getName(1)).thenReturn("Jim");
when(emp.getName(2)).thenReturn("Mark");

// Assert EmployeeExaminer's behavior:
assertTrue(ee.isJim(emp, 1));
assertFalse(ee.isJim(emp, 2));

It sounds like you may want to be using the .expects(1) type methods that mock frameworks usually provide.

Using mockito, if you were testing a List and wanted to verify that clear was called 3 times and add was called at least once with these parameters you do the following:

List mock = mock(List.class);        
someCodeThatInteractsWithMock();                 

verify(mock, times(3)).clear();
verify(mock, atLeastOnce()).add(anyObject());      

Source - MockitoVsEasyMock

If the contract of class A includes the fact that it calls method B of an object of type C, then you should test this by making a mock of type C, and verifying that method B has been called.

This implies that the contract of class A has sufficient detail that it talks about type C (which might be an interface or a class). So yes, we're talking about a level of specification that goes beyond just "system requirements", and goes some way to describing implementation.

This is normal for unit tests. When you are unit testing, you want to ensure that each unit is doing the "right thing", and that will usually include its interactions with other units. "Units" here might mean classes, or larger subsets of your application.

Update:

I feel that this doesn't apply just to verification, but to stubbing as well. As soon as you stub a method of a collaborator class, your unit test has become, in some sense, dependent on implementation. It's kind of in the nature of unit tests to be so. Since Mockito is as much about stubbing as it is about verification, the fact that you're using Mockito at all implies that you're going to run across this kind of dependency.

In my experience, if I change the implementation of a class, I often have to change the implementation of its unit tests to match. Typically, though, I won't have to change the inventory of what unit tests there are for the class; unless of course, the reason for the change was the existence of a condition that I failed to test earlier.

So this is what unit tests are about. A test that doesn't suffer from this kind of dependency on the way collaborator classes are used is really a sub-system test or an integration test. Of course, these are frequently written with JUnit too, and frequently involve the use of mocking. In my opinion, "JUnit" is a terrible name, for a product that lets us produce all different types of test.

how about you create an anonymous exception of type JsonProcessingException

when(mapper.writeValueAsString(any(Object.class))).thenThrow(new JsonProcessingException("Error"){});

The {} braces does the trick. This is much better since it is not confusing to the reader of the test code.