testing

name	testing
description	Consistent test structure for service and controller layers. Use when writing any new test or adding coverage.

Skill: Testing

When to load it: When writing any new test, or adding test coverage to an existing feature.

---

What This Skill Does

Produces unit tests for the service layer (plain JUnit + Mockito, no Spring context) and integration tests for the controller layer (@WebMvcTest). Enforces a consistent naming convention and test structure.

---

Rules

Unit tests (service layer):

• Use Mockito. No Spring context loaded. Fast.
• Test observable behavior, not internal implementation. Mock the boundary, not internals.
• One logical assertion per test is a guideline, not a law. Assert what matters.

Controller tests:

• Use @WebMvcTest. Do not load the full Spring context.
• Use MockMvc. Assert HTTP status and response body shape.
• Mock the service layer with @MockBean.

Naming: methodName_condition_expectedResult Example: getById_unknownId_returns404

---

Pattern

Unit test:

@ExtendWith(MockitoExtension.class)
class [Resource]ServiceTest {

    @Mock
    private [Dependency] dependency;

    @InjectMocks
    private [Resource]Service service;

    @Test
    void [methodName]_[condition]_[expectedResult]() {
        // Arrange
        given(dependency.[method]()).willReturn([value]);

        // Act
        [ReturnType] result = service.[method]([args]);

        // Assert
        assertThat(result).[assertion];
    }
}

Controller test:

@WebMvcTest([Resource]Controller.class)
class [Resource]ControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private [Resource]Service service;

    @Test
    void [methodName]_[condition]_[expectedResult]() throws Exception {
        given(service.[method]([args])).willReturn([value]);

        mockMvc.perform(get("/api/v1/[resource]/{id}", [id]))
            .andExpect(status().isOk())
            .andExpect(jsonPath("$.field").value([expected]));
    }
}

---

Design Constraints

• Do not use @SpringBootTest for tests that only need one layer
• Do not test Spring wiring in unit tests — that is what @WebMvcTest is for
• Do not assert on exact error message strings — assert on status codes or error type fields
• Do not name tests with test prefix or should — use method_condition_result