Why doesnt Springboot Mockmvc.perform handle exceptions on controller? - spring-boot

Question

I have written the following code and the mockmvc.perform does not catch exception instead returns an error stack. I used the debugger to confirm that the controller throws the correct error. I am new to SpringBoot and do not understand why the exception is not being handled by the test controller.The following is my test controller which makes three Api calls to external services.The exception is returned by the controller but Mockmvc.perform fails to assert it.
#ExtendWith(SpringExtension.class)
#SpringBootTest(classes = { Application.class, ApplicationTest.class })
#AutoConfigureMockMvc
#ContextConfiguration(initializers = {WireMockInitializer.class})
public class myControllerIntegrationTest {
#Autowired
private MockMvc mockMvc;
#Autowired private WireMockServer wireMockServer;
#Autowired
private myController myController;
#Before
public void setup() {
this.mockMvc = MockMvcBuilders.standaloneSetup(myController)
.build();
}
#Test
#DisplayName("Should Return Execution Error")
public void shouldReturnExecutionErrorOnService() throws Exception {
// Making Three Api calls the controller internally invokes them
configureStubA(HttpStatus.INTERNAL_SERVER_ERROR, args, "invalidResponse.json");
configureStubB(HttpStatus.INTERNAL_SERVER_ERROR, args, args2, args3,
"invalidResponse.json");
configureStubC(HttpStatus.INTERNAL_SERVER_ERROR, args, "invalidResponse.json");
mockMvc
.perform(
get("/something")
.param("a", a)
.param("b", b)
.param("c", c)
.param("d", d)
.param("e", e.toArray(new String[] {})))
.andDo(print())
.andExpect(status().is5xxServerError())
.andExpect(result -> assertTrue(result.getResolvedException() instanceof
IllegalStateException));
}}

Answer 1

The API itself will never return an exception.
Think of it as when you call an API, you'll always get a response, right?
The way Spring Controller handle an Exception is that it has a default exception handler, that will convert any exception threw from your Controller into a Response object, which will then be converted to json/xml and return to you.

Answer 2

One way to get what you are expecting is by declaring your own exception, annotate it with #ResponseStatus, and pass to it the http status code you want the exception to be mapped to.
For example (I'm using Kotlin in the following snippets) you can declare the mapping between the http status code 500 and your exception in this way:
#ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
class MyException(message: String) : RuntimeException(message)
Then in your test you will be able to assert on the internal error as you are doing in your snippet.
mockMvc.perform(get("/foo")).andExpect(status().isInternalServerError)
For more details take a look here and here