How to test these kinds of methods (from Service layer) - spring

Question

I'm fiddling around with Mockito and Spring MVC. I'm trying to write unit tests for the code I've just written.
This is my CategoryService class:
#Service
public class CategoryService {
#Autowired
#Qualifier("categoryDaoImpl")
private CategoryDao categoryDao;
public void addCategory(Category category) {
category.setId(getLastCategoryId() + 1);
categoryDao.addCategory(category);
}
public Category getCategoryById(int id) {
return categoryDao.getCategoryById(id);
}
public List<Category> getCategories() {
return categoryDao.getAllCategories();
}
public int getCategoriesCount() {
return categoryDao.getCategoriesCount();
}
public int getLastCategoryId() {
if (categoryDao.getAllCategories().size() == 0) {
return 0;
}
return Collections.max(categoryDao.getAllCategories()).getId();
}
public CategoryDao getCategoryDao() {
return categoryDao;
}
public void setCategoryDao(CategoryDao categoryDao) {
this.categoryDao = categoryDao;
}
I've already tested CategoryDao with nearly 100% coverage.
And now I want to test CategoryService, but I have no idea how to test it, I mean methods like: addCategory, getCategoryById, getAllCategories, getCategoiesCount etc.
They're just talking to the DAO pattern, but what if another person changes its logic? I'd be glad if you told me or showed how to write a tests for such short methods.
As far as CategoryService is concerned, I only wrote tests for getLastCategoryId():
#Test
public void shouldGetLastCategoryIdWhenListIsEmpty() {
//given
List<Category> list = new ArrayList<Category>();
Mockito.when(categoryDao.getAllCategories()).thenReturn(list);
//when
int lastCategoryId = categoryService.getLastCategoryId();
//then
assertThat(lastCategoryId, is(0));
}
#Test
public void shouldGetLastCategoryIdWhenListIsNotEmpty() {
//given
List<Category> list = new ArrayList<Category>();
list.add(new Category(1, "a", "a"));
list.add(new Category(3, "a", "a"));
list.add(new Category(6, "a", "a"));
Mockito.when(categoryDao.getAllCategories()).thenReturn(list);
//when
int lastCategoryId = categoryService.getLastCategoryId();
//then
assertThat(lastCategoryId, is(6));
}
Thank you very much for help :)
Best regards,
Tom

Answer 1

You need to verify that the service methods behave as per their contracts even if they are modified in the future.
For e.g. The addCategory(Category c) method adds the category. This can be verified by verifying the categoryDao.addCategory() method is called with the category object that has the required properties set. In this case the id should be set to the lastCategoryId. Verifying could simply be done by create a spy of CategoryDao class (would be simpler then using third party libraries like mockito.
The test cases for getCategoryById(), getCategories() and getCategoriesCount() method could verify that the values returned are the ones returned by the dao.
I understand that this would mean just one test case per method, but these test cases just confirm that if there is more logic added in the service method implementation, the contract remains intact.
Here's one test case for addCategory()
public class CategoryServiceTest {
private CategoryService service;
private CategoryDaoSpy daoSpy;
#Before
public void setUp() {
service = new CategoryService();
daoSpy = new CategoryDaoSpy();
service.setCategoryDao(daoSpy);
}
#Test
public void shouldSaveCategoryWhenCategoryPassed() {
Category category = new Category();
service.addCategory(category);
assertEquals(daoSpy.getAddCategoryCallCount(), 1);
assertEquals(daoSpy.getCategories().size(), 1);
assertEquals(daoSpy.getCategories().get(0).getId(), 1);
}
}
public class CategoryDaoSpy extends CategoryDao {
private int addCategoryCallCount = 0;
private List<Category> categories = new ArrayList<>();
#Override
public void addCategory(Category category) {
this.addCategoryCallCount++;
categories.add(category);
}
public int getAddCategoryCallCount() {
return addCategoryCallCount;
}
public List<Category> getCategories() {
return categories;
}
#Override
public List<Category> getAllCategories() {
return Collections.emptyList();
}
}