public List<Backend> getBackendOnlyWithHost(String host) {
        List<Backend> resultBackends = new ArrayList<>();
        for (Backend backend : idToBackendRef.values()) {
            if (backend.getHost().equals(host)) {
                resultBackends.add(backend);
            }
        }
        return resultBackends;
    }
@Test
    public void testGetBackendOnlyWithHost() throws Exception {

        Backend be = new Backend(10001, "newHost", 1000);
        be.setBePort(1001);
        service.addBackend(be);
        List<Backend> bes = service.getBackendOnlyWithHost("newHost");
        Assert.assertTrue(bes.size() == 1);
    }