public void ClusterHeartbeatSenderState_must_continue_to_use_Unreachable()
{
var s1 = _emptyState.AddMember(cc).AddMember(dd).AddMember(ee);
var s2 = s1.HeartbeatRsp(cc).HeartbeatRsp(dd).HeartbeatRsp(ee);
Fd(s2, ee).MarkNodeAsUnavailable();
s2.FailureDetector.IsAvailable(ee.Address).ShouldBeFalse();
s2.AddMember(bb).ActiveReceivers.ShouldBe(ImmutableHashSet.Create(bb,cc,dd,ee));
}