[wip] adding examples of testing with hyphothesis

[djarecka]

I added an example of tests with hyphothesis library.
I used the existing tests (and the test framework) for this example.

You can let me know what d you think about using hyphothesis in your project. If you like it, I can add more test. I'm learning hyphothesis, so you can also let me know if you have suggestion how to improve the tests.

[skrah]

This looks interesting --- I think I might want to revisit this if the project is at a later stage, so let's just keep the issue open. I haven't used hypothesis yet, so I can't say for sure if it is a good fit.