How to use shouldPrintStubWasUsedWithDifferentArgs method of org.mockito.internal.debugging.WarningsFinderTest class

Since Mockito 1.9.5+ and Java 8+

You can use a lambda expression, like:

when(myMock.myFunction(anyString())).thenAnswer(i -> i.getArguments()[0]);

Where i is an instance of InvocationOnMock.

For older versions

You can create an Answer in Mockito. Let's assume, we have an interface named MyInterface with a method myFunction.

public interface MyInterface {
    public String myFunction(String abc);
}

Here is the test method with a Mockito answer:

public void testMyFunction() throws Exception {
    MyInterface mock = mock(MyInterface.class);
    when(mock.myFunction(anyString())).thenAnswer(new Answer<String>() {
    @Override
    public String answer(InvocationOnMock invocation) throws Throwable {
        Object[] args = invocation.getArguments();
        return (String) args[0];
    }
    });

    assertEquals("someString",mock.myFunction("someString"));
    assertEquals("anotherString",mock.myFunction("anotherString"));
}

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.

As you noted, act is not a mock, and therefore you cannot record behavior on it. You could use Mockito.spy to, well, spy (or partially mock) the act object so that you only record the behavior of secondMethod and execute the actual code for firstMethod.

Note, however, that matchers can't be used in doReturn calls regardles of how you're mocking or spying your object. A return value must be a concrete object.

class ActivityTest() {

  Activity act;

  @Before
  public void setup(){
     act = Mockito.spy(new Activity()); // Here!
  }

  @Test
  public void testFirstMethod(){

      Mockito.doReturn("someString").when(act).secondMethod();
      act.firstMethod();
      verify(act).secondMethod();
  }
} 

A slightly more elegant syntax allows you to use annotations instead of explicitly calling Mockito.spy, but it's a matter of taste really:

@RunWith(MockitoJUnitRunner.class)
class ActivityTest() {

  @Spy
  Activity act = new Activity();

  @Test
  public void testFirstMethod(){

      Mockito.doReturn("someString").when(act).secondMethod();
      act.firstMethod();
      verify(act).secondMethod();
  }
} 

Since I didn't get any response here I asked on the Mockito forums. Here is a link to the discussion: https://groups.google.com/d/topic/mockito/hWwcI5UHFi0/discussion

To summarize the answers, technically this would kind of defeat the purpose of mocking. You should really only mock the objects needed by the SystemUnderTest class. Mocking things within objects that are themselves mocks is kind of pointless.

If you really wanted to do it, @spy can help

You can do it with Mockito and PowerMockito.

Say you have ClassUnderTest with a constructor

public class ClassUnderTest {
    String name;
    boolean condition;

    public ClassUnderTest(String name, boolean condition) {
       this.name = name;
       this.condition = condition;
       init();
    }

    ...
}

And another class that calls that constructor

public class MyClass {

    public MyClass() { } 

    public void createCUTInstance() {
       // ...
       ClassUnderTest cut = new ClassUnderTest("abc", true);
       // ...
    }

    ...
}

At the Test class we could...

(1) use PowerMockRunner and cite both target classes above in the PrepareForTest annotation:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ ClassUnderTest.class, MyClass.class })
public class TestClass {

(2) intercept the constructor to return a mock object:

@Before
public void setup() {
    ClassUnderTest cutMock = Mockito.mock(ClassUnderTest.class);
    PowerMockito.whenNew(ClassUnderTest.class)
                .withArguments(Matchers.anyString(), Matchers.anyBoolean())
                .thenReturn(cutMock);
}

(3) validate the constructor call:

@Test
public void testMethod() {
    // prepare
    MyClasss myClass = new MyClass();

    // execute
    myClass.createCUTInstance();

    // checks if the constructor has been called once and with the expected argument values:
    String name = "abc";
    String condition = true;
    PowerMockito.verifyNew(ClassUnderTest.class).withArguments(name, condition);
}

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

You're surprised that the writes on the new objects aren't writing through to the backing collection?

Collections.transform doesn't just do the transform "as needed" -- it doesn't store anything at all. That's what "view" means in its documentation. Any time you walk through a Collections2.transformed collection, it applies the function again, freshly. Once that for loop in the apply method is done with result, that object is gone; never seen again.

If you want to do what you're doing, make an explicit copy of the transformed collection in e.g. an ArrayList.

As the error message suggests, you cannot mock final classes with the default Mockito.

But the community came up with mockito-inline, an extension bringing experimental features such as mocking final classes and methods or static methods.

Just add this in your pom.xml and use Mockito normally.

<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-inline</artifactId>
    <scope>test</scope>
</dependency>

You need to replace the code inside the infinite loop with a function.

You then write a unit test for that function.