WIP: Make testsuite testable using DI

[gaehlerm]

If you want to test the output of the iPython notebook, I would recommend using dependency injection. Write a class iPythonGenerator and one DebugGenerator that implement all the output. Then you can use the DebugGenerator for testing and the iPythonGenerator for running the actual code.

Let me know if you have any questions.

And this is just a quick and dirty draft, to show the idea. No full implementation. In theory it could run, but I would be surprised if it did.