public void TestPurge()
 {
     QueueChannel channel = new QueueChannel(2);
     TimeSpan minute = new TimeSpan(0, 0, 1, 0);
     DateTime now = DateTime.Now;
     DateTime past = now.Subtract(minute);
     DateTime future = now.Add(minute);
     IMessage expiredMessage = MessageBuilder.WithPayload("test1").SetExpirationDate(past).Build();
     IMessage unexpiredMessage = MessageBuilder.WithPayload("test2").SetExpirationDate(future).Build();
     Assert.IsTrue(channel.Send(expiredMessage, TimeSpan.Zero));
     Assert.IsTrue(channel.Send(unexpiredMessage, TimeSpan.Zero));
     Assert.IsFalse(channel.Send(new StringMessage("atCapacity"), TimeSpan.Zero));
     IList<IMessage> purgedMessages = channel.Purge(new UnexpiredMessageSelector());
     Assert.IsNotNull(purgedMessages);
     Assert.That(purgedMessages.Count, Is.EqualTo(1));
     Assert.IsTrue(channel.Send(new StringMessage("roomAvailable"), TimeSpan.Zero));
 }