I am fairly new to spring boot. I am trying to test this service class if it throws the IllegalArgumentException.class but somehow the exception is not thrown. Help me get what I am missing. This is a section of the service class:

   public ResponseEntity<ModelApiResponse> createResponse(Response response)
            throws JsonProcessingException, IllegalArgumentException{
        try{
            myRepository.save(response);

            return new ResponseEntity<>(HttpStatus.valueOf(GlobalVariables.RESPONSE_CODE_201));
        } catch (IllegalArgumentException ex){

            return new ResponseEntity<>(HttpStatus.valueOf(GlobalVariables.RESPONSE_CODE_500));
        }
    }

I have tried two test methods. The test method (1):

  @Test
    public void testThatResponseCreationThrowsErrorWhenSavingFails() throws Exception{
        Response responseMock = mock(Response.class);
        when(abbyResponseRepositoryMock.save(new Response())).thenThrow(IllegalArgumentException.class);

        assertThrows(IllegalArgumentException.class, () -> abbyResponseRepositoryMock.save(abbyResponseMock));

    }

Test method two:

   @Test
    public void testThatResponseCreationThrowsErrorWhenSavingFails() throws Exception {
        Mockito.when(chatResponseRepositoryMock.save(new Response())).thenThrow(Mockito.mock(IllegalArgumentException.class));

        Response response = new Response();
        Response.setMessage("This is a unit test response message");
        Response.setNxtMessageId("98765");

        mockMvc.perform(post("/api/v1/responses/create-response")
                .header(HttpHeaders.AUTHORIZATION, "Basic " + "credentials")
                .header(GlobalVariables.X_CORRELATION_ID, "123456")
                .header(GlobalVariables.X_SOURCE_APP, "source_app")
                .header(GlobalVariables.X_USER, "user")
                .header(GlobalVariables.X_USER_ROLE, "user")
                .content(this.json(response))
                .contentType(contentType))
                .andExpect(jsonPath("$.header.responseCode", is(500)))
                .andExpect(jsonPath("$.header.responseMessage", is("Error saving chat response")))
                .andReturn();
    }

Also advise on which test method would be suitable. The controller is just a basic controller class that calls the service class to save a chat response. The service class on the other hand calls the repository to save the chat response.

output:

Expected: is <500>
     but: was <201>