public void TestEmpty() { var lookup = AsyncLookup <int, int> .ToLookup(AsyncEnum.Empty <int>(), x => x, null); Assert.IsFalse(lookup.ContainsAsync(1).AwaitSynchronously()); var seq = lookup.GetAsync(1).AwaitSynchronously(); Assert.IsNotNull(seq); Assert.AreEqual(0L, seq.CountAsync().AwaitSynchronously()); }