public async void WhenGivenOnlyAGuidGenerator_ShouldGenerateGuidInDefaultProperty()
        {
            var handler = new ValueMessageHandler(new GuidValueGenerator());

            var msg = new Message();
            await handler.ProcessMessageAsync(msg, "pipeline", 1);

            Assert.Equal(1, msg.Properties.Count);
            Assert.True(msg.Properties.ContainsKey("guid"), "Message should contain a property named 'guid'");

            var s = msg.Properties["guid"];
            var g = Guid.Parse(s);

            Assert.IsType(typeof(Guid), g);
        }
        public async void WhenGivenOnlyARandomIntGenerator_ShouldGenerateIntInDefaultProperty()
        {
            var handler = new ValueMessageHandler(new RandomIntValueGenerator());

            var msg = new Message();
            await handler.ProcessMessageAsync(msg, "pipeline", 0);

            Assert.Equal(1, msg.Properties.Count);
            Assert.True(msg.Properties.ContainsKey("rnd"), "Message should contain a property named 'rnd'");

            var s = msg.Properties["rnd"];
            var i = int.Parse(s);

            Assert.True(i >= 0);
        }