How do you test exception handling and @ControllerAdvice with MockMvc? MockMvc के साथ एक्सेप्शन हैंडलिंग और @ControllerAdvice को कैसे टेस्ट करें?

Since @WebMvcTest loads the full MVC layer, including any @ControllerAdvice classes in the tested package, exception handling can be verified by stubbing a mocked service to throw the target exception and then asserting on the response status and body returned by the global exception handler.

This confirms not just that the controller calls the service correctly, but that the entire error-response pipeline — exception thrown, caught by @ExceptionHandler, mapped to the correct HTTP status and JSON error shape — works end-to-end without needing a full @SpringBootTest.

@Test
void getUser_notFound_returns404() throws Exception {
    when(userService.findById(99L)).thenThrow(new ResourceNotFoundException("User not found"));

    mockMvc.perform(get("/api/users/99"))
        .andExpect(status().isNotFound())
        .andExpect(jsonPath("$.message").value("User not found"));
}