Can multiple mocks of a class be used in a single test class?

Question

I have a class:

classA
{
    private Boolean isEnable;

    private final Config config;

    public classA(final Config config)
    {
        this.config = config;
        isEnable = config.getEnablingStatus();
    }

    public classB fun()
    {
        // Do something!
        // Return an object of classB!
    }
}

I want to test the method fun() in 2 different scenarios - one in which isEnable is true, and one in which it's false.

So, to do that I am thinking of having 2 different instances of the classA in its test class:

TestClassForClassA
{
    private Boolean isEnable;
    
    @Mock
    private final Config config;
   
    @InjectMocks
    classA objAWithIsEnableAsTrue, objAWithIsEnableAsFalse;

    @Before
    public void init() 
    {
        initMocks(this);
    }

    public void testFunWhenIsEnableIsTrue()
    {
        doReturn(true).when(config).getEnablingStatus();
        objAWithIsEnableAsTrue = new classA(config);
        // Use the objAWithIsEnableAsTrue object in this test method.
    }

    public void testFunWhenIsEnableIsFalse()
    {
        doReturn(false).when(config).getEnableStatus();
        objAWithIsEnableAsFalse = new classA(config);
        // Use the objAWithIsEnableAsFalse object in this test method.
    }
}

Can it be done like this? If not what is the right way to do it?

Answer 1

This is not the answer to the question you wrote but I guess it could be the answer you need:

From the code you posted there is no reason to mock classA. In the @Before annotated method you even instantiate the objects by calling the constructor. This means those objects (objAWithIsEnableAsTrue and objAWithIsEnableAsFalse) are not even mocked in your tests.

---

In order to make your tests more clear, I would suggest moving the setup logic of your tests into the test methods themselves.

TestClassForClassA {

    @Test
    public void testFunWhenIsEnableIsTrue(){
        Config config = mock(Config.class);
        doReturn(true).when(config).getEnableStatus();

        classA objAWithIsEnableAsTrue = new classA(config);
        // Use the objAWithIsEnableAsTrue object in this test method.
    }

    @Test
    public void testFunWhenIsEnableIsFalse(){
        Config config = mock(Config.class);
        doReturn(false).when(config).getEnableStatus();

        classA objAWithIsEnableAsfalse = new classA(config);
        // Use the objAWithIsEnableAsTrue object in this test method.
    }
}

Also, you should check if you really need to mock the Config object. Can it also be instantiated without side effects? If yes, I would do so to get rid of the whole mocking.

Config config = new Config(); 
config.setEnablingStatus(true); // maybe do this instead of mocking?