Verifying that setter was called on mocked object with Mockito

Question

Given the following service method in a Spring Boot application:

@Transactional
public void updateCategory(long categoryId, CategoryData categoryData) {
  final Category category = categoryRepository.findById(categoryId).orElseThrow(EntityNotFoundException::new);
  category.setName(categoryData.getName());
}

I know how to instruct Mockito to mock the categoryRepository.findById() result.

However, I couldn't figure out yet: Is it possible to verify that category.setName() was called with the exact argument of categoryData.getName()?

Answer 1

You are looking for Mockito.verify, and a test looking like:

@ExtendWith(MockitoExtension.class)
public class CategoryServiceTest {
    @Mock
    CategoryRepository categoryRepository;

    @InjectMocks
    CategoryService categoryService;

    @Test
    public void testUpdateCategoryMarksEntityDirty() {
        // given
        long categoryId = 1L;
        Category category = mock(Category.class);
        String newCategoryName = "NewCategoryName";
        when(categoryRepository.findById(categoryId)).thenReturn(Optional.of(category));

        // when
        categoryService.updateCategory(categoryId, new CategoryData(newCategoryName));

        // then
        verify(category, times(1)).setName(newCategoryName);
    }
}

I must, however, advise against this style of testing.

Your code suggests that you are using a DB Access library with dirty-checking mechanism (JPA / Hibernate?). Your test focuses on the details of interaction with your DB Access layer, instead of business requirement - the update is successfully saved in the DB.

Thus, I would opt for a test against a real db, with following steps:

• given: insert a Category into your DB
• when: CategoryService.update is called
• then: subsequent calls to categoryRepository.findById return updated entity.