Test for internal server errors in rest api

Question

I want to write unit test cases for negative scenarios for my REST API spring boot application.

The controller methods looks like this:

@RequestMapping(path = "/getcalc/srn/{srn}", method = RequestMethod.GET)
    public RestResponse<List<BookMarkMRPostProcessCalc>> fetchLatestPostProcessCalc(@PathVariable("srn") String srn) {
        try {
            List<BookMarkMRPostProcessCalc> calcList = bookMarkMrPostProcessCalcService.getPostProcessCalc(srn);
            return ResponseUtil.prepareRestResponse(calcList);
        } catch (BookMarkServiceException e) {
            return ResponseUtil.prepareErrorRestResponse(e.getMessage(), "", e.toString());
        }
    }

The positive scenario works fine. I want to write test cases for the scenario when BookMarkServiceException occurs or mock it. How can we achieve this in junit?

Answer 1

One way of doing it is as below:

@RunWith(SpringRunner.class)
public class YourClassNameTest { 

@InjectMocks
pricvate YourClassName yourClassName;

@Rule
public ExpectedException exceptionRule = ExpectedException.none();

@Test
public void fetchLatestPostProcessCalcTest(){
    expectedException.expect(BookMarkServiceException.class);
    yourClassName.fetchLatestPostProcessCalc("input that would generate error");
}