Eddú Meléndez

JUnit and Mockito

As you maybe know, JUnit is a java testing framework.

Before to talk about our mock framework, we need to be in the same page about what mock is?

Marting Fowler in his article Mocks are not Stubs said:

Mocks are objects pre-programmed with expectations which form a specification of the calls they are expected to receive.

Mockito is the mock framework which we will use.

Lets start with the example, first of all we need to setup our Maven project.

1. Adding dependencies

pom.xml
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<dependencies>
  <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.10</version>
      <scope>test</scope>
  </dependency>
  <dependency>
      <groupId>org.mockito</groupId>
      <artifactId>mockito-all</artifactId>
      <version>1.8.5</version>
      <scope>test</scope>
  </dependency>
</dependencies>

2. In this example, we will use annotations so we have three ways to enable them.

UserServiceImplTest.java
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@RunWith(MockitoJUnitRunner.class)               //First method to enable mockito's annotations
public class UserServiceImplTest {

  @Rule
  public MockitoRule rule = MockitoJUnit.rule();    //Second method to enable mockito's annotations

  @Before
  public void setup() {
      MockitoAnnotations.initMocks(this);      //Third method to enable mockito's annotations
  }

}

Note: You can use one of them. I suggest the use of MockitoRule in favor of use another runners like org.junit.runners.Parameterized

3. UserServiceImpl HAS-A UserRepository. For that reason, create a UserRepository mock and it will be injected in UserServiceImpl. Then, we can mock UserRepository methods as you can see in step 3.

UserServiceImplTest.java
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public class UserServiceImplTest {

  @Mock                               //1. Create UserRepository mock object
  UserRepository userRepository;

  @InjectMocks                        //2. Insert UserRepository mock object into UserService
  UserService userService = new UserServiceImpl();

  @Before
  public void setup() {
      //MockitoAnnotations.initMocks(this);
  }

  @Test
  public void testSomething() {
      String username = "emelendez";
      Mockito.when(userRepository.getPassword(username)).thenReturn("PasswordMock"); //3. Mocking objects
      userService.validateCredential(username);
      Mockito.verify(userRepository).getPassword(username);
  }

}

You can download the source code here

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