private void ConfigureSocketAcceptAsyncResult(bool receiveData) { _serverSocket.SocketMock.Setup(x => x.AcceptAsync(_serverAcceptor.SocketEvent)).Returns<SocketAsyncEventArgs>(x => { bool instantReceive = receiveData; receiveData = !receiveData; _serverAcceptor.SocketEvent.SocketError = SocketError.Success; _serverAcceptor.SocketEvent.AcceptSocket = instantReceive ? _acceptedSocket.GetSocket() : null; return !instantReceive; // returning false because "AcceptAsync()" returns false if accepted instantly }); }