public void Group_Send_AllClientsShouldBeReceiveEvent() { var group = new FlowGroup(server); group.Add(destinationClients[0]); group.Add(destinationClients[2]); var transferString = "Hello client under index 0 & 2"; var expected = new HashSet <int> { 0, 2 }; var receivedOn = new HashSet <int>(); for (var i = 0; i < clients.Length; i++) { var index = i; clients[i].Bind <string>(1, value => { receivedOn.Add(index); }); } group.Send(1, transferString); Thread.Sleep(MillisecondsToWaitForTransfer); receivedOn.Should().BeEquivalentTo(expected); }