public ManagedChannel get(WindmillServiceAddress windmillServiceAddress) {
    return channelCache.getUnchecked(windmillServiceAddress);
  }
@Test
  public void testLoadingCacheReturnsLoadsChannelWhenNotPresent() {
    String channelName = "existingChannel";
    ManagedChannel channel = newChannel(channelName);
    Function<WindmillServiceAddress, ManagedChannel> channelFactory =
        spy(
            new Function<WindmillServiceAddress, ManagedChannel>() {
              @Override
              public ManagedChannel apply(WindmillServiceAddress windmillServiceAddress) {
                return channel;
              }
            });

    cache = newCache(channelFactory);
    WindmillServiceAddress someAddress = mock(WindmillServiceAddress.class);
    ManagedChannel cachedChannel = cache.get(someAddress);
    assertSame(channel, cachedChannel);
    verify(channelFactory, times(1)).apply(eq(someAddress));
  }