CODEWITHSUNDEEP
unit-testingjava-8predicate
user3375659
user3375659

Reputation: 65

Unit Testing Java 8 Predicates

I have a Java 8 Predicate like this. How do I write unit test for this

 Predicate<DTO> isDone = (dtO) ->
                (!dto.isFinished() &&
                !dto.isCompleted());

Thanks

Upvotes: 2

Views: 13857

Answers (2)

g-t
g-t

Reputation: 1533

I would test it like that:

private final Predicate<DTO> isDone = (dto) ->
        (!dto.isFinished() && !dto.isCompleted());

@Test
public void a() throws Exception {
    // given
    DTO dto = new DTO(true, true);

    // when
    boolean result = isDone.test(dto);

    // then
    assertThat(result).isFalse();
}

@Test
public void s() throws Exception {
    // given
    DTO dto = new DTO(true, false);

    // when
    boolean result = isDone.test(dto);

    // then
    assertThat(result).isFalse();
}

@Test
public void d() throws Exception {
    // given
    DTO dto = new DTO(false, true);

    // when
    boolean result = isDone.test(dto);

    // then
    assertThat(result).isFalse();
}

@Test
public void f() throws Exception {
    // given
    DTO dto = new DTO(false, false);

    // when
    boolean result = isDone.test(dto);

    // then
    assertThat(result).isTrue();
}

@AllArgsConstructor
public static class DTO {
    private final boolean isFinished;
    private final boolean isCompleted;

    public boolean isFinished() {
        return isFinished;
    }

    public boolean isCompleted() {
        return isCompleted;
    }
}

Instead of a, s, and f name the tests properly like: should_be_done_when_it_is_both_finished_and_completed.

I suppose DTO is just a value object so I'd rather create real instance instead of using mock.

Upvotes: 4

Lachezar Balev
Lachezar Balev

Reputation: 12021

If you have a reference to the predicate (as it seems in your example) then I see no issues. Here is simple example with Mockito/JUnit:

@Mock
private DTO mockDTO;

@Test
public void testIsDone_Finished_NotComplete()
{
    when(mockDTO.isFinished()).thenReturn(true);
    when(mockDTO.isCompleted()).thenReturn(false);

    boolean expected = false;
    boolean actual = isDone.test(mockDTO);

    Assert.assertEquals(expected, actual);
}

Upvotes: 2

Related Questions