Spring MockMvc Controller Testing | Java Fresher Interview

Direct Answer

Use @WebMvcTest(Controller.class) with MockMvc to test Spring MVC routing, request binding, validation, serialization, controller advice, and configured filters without a live server. Replace a controller collaborator with current @MockitoBean (legacy Boot code uses deprecated @MockBean). If Spring Security is present, its filter chain is normally part of the slice, so authenticate the request or deliberately configure the test boundary.

Code Example

@WebMvcTest(OrderController.class)
class OrderControllerTest {
    @Autowired MockMvc mvc;
    @MockitoBean OrderService service;

    @Test
    @WithMockUser
    void returnsAnOrder() throws Exception {
        when(service.find(7L)).thenReturn(new OrderResponse(7L, "READY"));

        mvc.perform(get("/orders/{id}", 7L))
           .andExpect(status().isOk())
           .andExpect(jsonPath("$.id").value(7))
           .andExpect(jsonPath("$.status").value("READY"));
    }
}

Common Mistakes & Pitfalls

• Calling it a plain unit test: a @WebMvcTest still creates a Spring test context.
• Forgetting collaborators: services outside the MVC slice must be imported or overridden.
• Ignoring security: a request can return 401 or 403 before reaching the controller.
• Forgetting CSRF: state-changing requests with CSRF protection enabled need a valid test token.
• Overstating standalone setup: it does not reproduce every MVC component unless configured.