[Unit Testing] Using Mockito Annotations - @Mock, @InjectMocks, @RunWith

Previously we have seen how to do Unit testing with Mockito;

import org.junit.Test;

import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

public class SomeBusinessMockTests {

    @Test
    public void testFindTheGreatestFromAllData() {
        DataService mockService = mock(DataService.class);
        when( mockService.retieveAllData()).thenReturn(new int[] {24, 6, 15});

        SomeBusinessImpl businessImpl = new SomeBusinessImpl(mockService);
        int result = businessImpl.findTheGreatestFromAllData();
        assertEquals(24, result);
    }
}

In this post, we are going to see, using annotation from Mockito to make testing easier:

@RunWith(MockitoJUnitRunner.class)
public class SomeBusinessMockTests {

    @Mock
    DataService mockService;

    @InjectMocks
    SomeBusinessImpl businessImpl;

    @Test
    public void testFindTheGreatestFromAllData() {

        when( mockService.retieveAllData()).thenReturn(new int[] {24, 6, 15});
        assertEquals(24, businessImpl.findTheGreatestFromAllData());
    }
}    

We need to place @RunWIth for the Test class, otherwise it won't work.

@Mock makes it easier to create a mock class.

@InjectMock makes it easier to inject created mock into a class.