private TimeSpan ProcessDelay(TimeSpan delay, double playbackSpeed)
{
var sw = new Stopwatch();
var reader = new Mock<IRecordedMessageReader>();
var engine = new RecordedMessageDelayEngine(reader.Object);
reader.SetupGet(x => x.PlaybackSpeed).Returns(playbackSpeed);
sw.Start();
var processed = engine.Process(new SetNextMessageDelayMessage(delay));
sw.Stop();
Assert.True(processed);
reader.VerifyAll();
return sw.Elapsed;
}