Mocking with Mockito

Here is an example of using Mockito to mock a service. The service used in this example, is a fictitious PersonService which returns Person objects based on their name. It might do this by connecting to a external database. In our unit tests, we don't want to connect to an external database, hence the reason for creating a mock. The mocked version shown below always returns a new Person object with the name that was passed into the service.

import static org.mockito.Matchers.anyString;
import static org.mockito.Mockito.when;
import static org.junit.Assert.*;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;

public class PersonServiceTest {

  @Mock private PersonService personService;

  @Before
  public void setUp() {
    MockitoAnnotations.initMocks(this);
    when(personService.getPerson(anyString())).thenAnswer(
      new Answer<Person>() {
        @Override
        public Person answer(InvocationOnMock invocation) throws Throwable {
          Object[] args = invocation.getArguments();
          return new Person((String)args[0]);
        }
      });
  }

  @Test
  public void testGetPerson(){
    assertEquals("Alice", personService.getPerson("Alice").getName());
  }
}