// 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);