@Test
    void updateServerRefOnEmptyDiscoveryResult() {
        OriginName originName = OriginName.fromVip("vip", "test");
        DefaultClientConfigImpl clientConfig = new DefaultClientConfigImpl();
        DynamicServerResolver resolver = mock(DynamicServerResolver.class);

        when(resolver.resolve(any())).thenReturn(DiscoveryResult.EMPTY);

        DefaultClientChannelManager clientChannelManager =
                new DefaultClientChannelManager(originName, clientConfig, resolver, new DefaultRegistry());

        AtomicReference<DiscoveryResult> serverRef = new AtomicReference<>();

        Promise<PooledConnection> promise = clientChannelManager.acquire(
                new DefaultEventLoop(), null, CurrentPassport.create(), serverRef, new AtomicReference<>());

        Truth.assertThat(promise.isSuccess()).isFalse();
        Truth.assertThat(serverRef.get()).isSameInstanceAs(DiscoveryResult.EMPTY);
    }
Tests for {@link DefaultClientChannelManager}.  These tests don't use IPv6 addresses because {@link InstanceInfo} is
not capable of expressing them.
zuul-core/src/test/java/com/netflix/zuul/netty/connectionpool/DefaultClientChannelManagerTest.java