Add/stream test scaffolds#tmp 164

@markstuart @matt-in-a-hat @Resonance1584 @WayneKoorts @andrewm-mediasuite 

**RFC** ;)

Testing streams... Heres my first attempt. I've created a stream spy that buffers up the stream and returns it in a callback all at once so you can then assert things about what happened in the stream. Then you can just plug in your transforms for testing

Thoughts?