java - Use Mockito 2.0.7 to mock lambda expressions

Question

I want to mock a query provided on my repository like this:

@Test
public void GetByEmailSuccessful() {
    // setup mocks
    Mockito.when(this.personRepo.findAll()
            .stream()
            .filter(p -> (p.getEmail().equals(Mockito.any(String.class))))
            .findFirst()
            .get())
            .thenReturn(this.personOut);
    Mockito.when(this.communityUserRepo.findOne(this.communityUserId))
            .thenReturn(this.communityUserOut);
...

My @Before method looks like this:

@Before
public void initializeMocks() throws Exception {
    // prepare test data.
    this.PrepareTestData();

    // init mocked repos.
    this.personRepo = Mockito.mock(IPersonRepository.class);
    this.communityUserRepo = Mockito.mock(ICommunityUserRepository.class);
    this.userProfileRepo = Mockito.mock(IUserProfileRepository.class);
}

Sadly when I run the test I receive the error:

java.util.NoSuchElementException: No value present

When I double-click the error it points at the .get() method of the first lambda.

Have any of you successfully mocked a lambda expression and know how I can solve my problem?

Answer 1

There's no need to mock such deep calls. Simply mock personRepo.findAll() and let the Streaming API work as normal:

Person person1 = ...
Person person2 = ...
Person person3 = ...
List<Person> people = Arrays.asList(person1, person2, ...);
when(personRepo.findAll()).thenReturn(people);

And then instead of

.filter(p -> (p.getEmail().equals(Mockito.any(String.class))))

just set/mock email on your Person objects to be the expected value.

Alternatively, consider implementing PersonRepo.findByEmail.