How to use single_mismatch_with_multiple_invocations method of org.mockito.internal.junit.ArgMismatchFinderTest class

I found the faulty part.

I changed

@RunWith(MockitoJUnitRunner.class)

to

@RunWith(PowerMockRunner.class)

Now the mocking works. But i have to say that as Jon Skeet printed out, the enum does not have everywhere that mocked member-instance. So in another Unit test calling MyEnum.CONSTANT.sayHello(); will print again it works instead of Hello!.

You can use

  Mockito.doAnswer(new Answer<Void>() {
        @Override
        public Void answer(InvocationOnMock invocation) throws Throwable {
            //DO SOMETHING
            return null;
        }
    }).when(...).remove(Matchers.<String>anyVararg());

From the Javadoc:

Use doAnswer() when you want to stub a void method with generic Answer.

Stubbing voids requires different approach from Mockito.when(Object) because the compiler does not like void methods inside brackets...

Example:

    doAnswer(new Answer() {
    public Object answer(InvocationOnMock invocation) {
        Object[] args = invocation.getArguments();
        Mock mock = invocation.getMock();
        return null;
    }}).when(mock).someMethod();

See examples in javadoc for Mockito

You are looking for an ArgumentCaptor:

  Mock mock =  Mockito.mock(Mock.class);
  ArgumentCaptor<String> captor = ArgumentCaptor.forClass(String.class);
  mock.method("input");
  Mockito.verify(mock).method(captor.capture());
  String actualValue = captor.getValue();

Just incase any M1 Mac users stumble onto this page like I did.

My Issue -

My spring boot project with wiremock tests, would run on my old intel mac but failed to run when I moved to my new M1 Mac.

_ _

I had 2 error messages

• java.lang.IllegalStateException: No Server ALPNProcessors!
• Suppressed: java.lang.UnsatisfiedLinkError: no conscrypt_openjdk_jni-osx-aarch_64

Fix -

I needed a property to test.application

wiremock.server.httpsPort=-1

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).

This feature is builtin since Mockito 1.9.5. Just use

mock(ClassToMock.class, withSettings().verboseLogging())

.. Reading Javadoc helps:

In rare cases when the parameter is a primitive then you must use relevant intThat(), floatThat(), etc. method. This way you will avoid NullPointerException during autounboxing.

You can set a default answer for a mock. All methods that aren't stubbed will use this default answer.

public void testUnstubbedException() {
    // Create a mock with all methods throwing a RuntimeException by default
    SomeClass someClass = mock( SomeClass .class, new RuntimeExceptionAnswer() );

    doReturn(1).when(someClass).getId(); // Must use doReturn

    int id = someClass.getId(); // Will return 1

    someClass.unstubbedMethod(); // Will throw RuntimeException
}

public static class RuntimeExceptionAnswer implements Answer<Object> {

    public Object answer( InvocationOnMock invocation ) throws Throwable {
        throw new RuntimeException ( invocation.getMethod().getName() + " is not stubbed" );
    }

}

Note that you cannot use when with this functionality, since the method is called before when (How does mockito when() invocation work?) and it will throw a RuntimeException before the mock goes into stubbing mode.

Therefore, you must use doReturn for this to work.

On a first glance, the answer is simply: well, there are several mocking frameworks out there, and there are different ways to use them.

The first example tells JUnit to use the "unit test runner" that the Mockito mocking framework provides. The second example uses the unit test runner from the PowerMock framework.

In order for things to make sense, you would also have different import statements, as both frameworks have different implementations for the @Mock annotation for example.

( the main point of using these framework-specific test runners is that they take care of initializing all the fields with special framework-specific annotations ).

So: the difference here is simply that: the first example is written to use the Mockito framework, the second one uses PowerMock.

Now, which one of those to use?

Answer: Mockito.

Why? Somehow an ugly truth is: the PowerMock-one basically is a cry for help. It says "the class under test is badly designed, please fix it". Meaning: as a developer, you can write "easy to test" code, or "hard to test" code. Many people do the second: they write code that is hard to test. And then, PowerMock(ito) provides means to still test that code.

PowerMock(ito) gives you the ability to mock (thus control) calls to static methods, and to new(). To enable that, PowerMock(ito) manipulates the byte code of your code under test. That is perfectly fine for small code bases, but when you face millions of lines of production code, and thousands of unit tests, things are totally different.

I have seen many PowerMock tests fail for no apparent reason, to find out hours later ... that some "static" thing somewhere else was changed, and that somehow affect a different PowerMock static/new driven test case.

At some point, our team made a conscious decision: when you write new code, and you can only test that with PowerMock ... that isn't acceptable. Since then, we only created Mockito test cases, and not once since then we saw similar bizarre problems that bugged us with PowerMock.

The only acceptable reason to use PowerMock is when you want to test existing (maybe 3rd party) code that you do not want to modify. But of course, what is the point of testing such code? When you can't modify that code, why should tests fail all of a sudden?