CODEWITHSUNDEEP
javamockitojunit5
c_anirudh
c_anirudh

Reputation: 394

Is it required to define doNothing()/when() on Objects mocked using Mockito

I am writing unit tests using JUnit5 and Mockito for a class Main.java.

The dependency class ExternalApi.java is injected in Main.java.

Here is my MainTest.java:

@ExtendWith(MockitoExtension.class)
public class MainTest {
    @InjectMocks
    Main main;

    @Mock
    ExternalApi externalApi;

    @Test
    void testAbcMethod() {

    }
}

The abc() method in Main.java calls externalApi.doSomething() which does some stuff.

I don't want this original externalApi method to be called in my test. Do I need to define

doNothing().when(externalApi).when(doSomething());

or is it just enough to mock ExternalApi?

What happens when we don't define what happens when we call a mocked object's methods?

Upvotes: 1

Views: 1920

Answers (1)

exaucae
exaucae

Reputation: 2675

What happens when we don't define what happens when we call a mocked object's methods?

Nothing happens. Mocking is enough since it's not the real class/method that is called but the mocked one.

If you had spied on the instance, that would have triggered the real method call. Only then, you'd have thought of using doNothing to silence the method behavior.


@Test
public void whenNotDefineBehaviorOnMock_thenCorrect() {
    List mockList = Mockito.mock(ArrayList.class);
    
   // No behavior defined,
    mockList.add("one");
    Mockito.verify(mockList).add("one");
   // Size is still empty
    assertEquals(0, mockList.size());

   // Behavior defined
    Mockito.when(mockList.size()).thenReturn(100);
    assertEquals(100, mockList.size());
}

Upvotes: 5

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