How do I unit test a Servlet Filter with jUnit?

Question

Implemented doFilter(). How to properly cover Filter with jUnit ?

public void doFilter(ServletRequest servletRequest, ServletResponse servletRes         


        

Answer 1

If you are using Spring then it has own mocks:

• org.springframework.mock.web.MockFilterChain
• org.springframework.mock.web.MockHttpServletRequest
• org.springframework.mock.web.MockHttpServletResponse

For example, you can add headers and set test Uri.

So your test can be smth like this:

@RunWith(MockitoJUnitRunner.class)
public class TokenAuthenticationFilterTest {

    private static final String token = "260bce87-6be9-4897-add7-b3b675952538";
    private static final String testUri = "/testUri";

    @Mock
    private SecurityService securityService;

    @InjectMocks
    private TokenAuthenticationFilter tokenAuthenticationFilter = new TokenAuthenticationFilter();

    @Test
    public void testDoFilterInternalPositiveScenarioWhenTokenIsInHeader() throws ServletException, IOException {
        MockHttpServletRequest request = new MockHttpServletRequest();
        request.addHeader(TOKEN, token);
        request.setRequestURI(testUri);
        MockHttpServletResponse response = new MockHttpServletResponse();
        MockFilterChain filterChain = new MockFilterChain();
        when(securityService.doesExistToken(token)).thenReturn(true);
        tokenAuthenticationFilter.doFilterInternal(request, response, filterChain);
        assertThat(response.getStatus()).isEqualTo(HttpStatus.OK.value());
    }
}