public static boolean isServletRequestAuthenticatorInstanceOf(Class<? extends ServletRequestAuthenticator> clazz) {
        final AuthCheckFilter instance = getInstance();
        if (instance == null) {
            // We've not yet been instantiated
            return false;
        }
        return servletRequestAuthenticator != null && clazz.isAssignableFrom(servletRequestAuthenticator.getClass());
    }
@Test
    public void willReturnTrueIfTheCorrectServletRequestAuthenticatorIsConfigured() {

        new AuthCheckFilter(adminManager, loginLimitManager);
        AuthCheckFilter.SERVLET_REQUEST_AUTHENTICATOR.setValue(NormalUserServletAuthenticatorClass.class);

        assertThat(AuthCheckFilter.isServletRequestAuthenticatorInstanceOf(NormalUserServletAuthenticatorClass.class), is(true));
    }