// Verify
        assertNotNull(result);
        assertEquals("https://example.com/logout", result);
        assertNull(authenticator.getLastLogoutUser());
    }

    @Test
    public void test_logout_returnsNull() {
        // Setup
        FessUserBean user = FessUserBean.empty();
        authenticator.setLogoutUrl(null);

        // Execute
        String result = authenticator.logout(user);

        final String url = authenticator.buildDefaultRedirectUrl();
        assertEquals("http://localhost:8080/sso/", url);
    }

    @Test
    public void test_logout_returnsNull() {
        assertNull(authenticator.logout(null));
    }

    @Test
    public void test_getResponse_returnsNull() {
        assertNull(authenticator.getResponse(null));
    }

    @Test