Adds Module 6: Testing Code

[rsokl]

@davidmascharka (and anyone else!) I am in the process of completing an early draft of Module 6. I will make note of the sections that are ready for review/edits below. Thank you for your help!

I have pushed a temporary branch that has the updated html for this WIP - so that you can read the content as it would appear on the website. The branch is here. You can clone/download it and view index.html in your browser to get to the PLYMI home page.

Ready for Review

• [x] module6.rst
• [x] Intro_to_Testing.md
• [x] Pytest.md
• [ ] Hypothesis.md

[rsokl]

@edkek @Zac-HD @petarmhg thanks so much for the great edits and feedback!

My plans for the upcoming sections are:

• Introduction to Hypothesis
  • Describing data with strategies
  • Shrinking and reproducing failcases
• Testing numerical code
  • Using hypothesis.extra.numpy
  • Absolute and relative tolerance for comparing floating point numbers
  • Leveraging numpy.testing utilities; e.g. assert_allclose
• Property based testing
  • Rerwriting our oracle tests as property-based tests
  • Maybe....introduce metamorphic testing

[rsokl]

@davidmascharka thanks so much for the careful readthrough that you did - you caught many crucial flubs on my part! Let me know what you think once you have given it a qualitative readthrough

[rsokl]

@davidmascharka @Zac-HD

Hypothesis.md should be ready for review.

(Edit: actually I am realizing that I still have to introduce .map and .filter, along with interactive drawing... So it is ready to review up through the core strategies)

(Edit: okay, I added the discussions for .map and .filter, along with interactive drawing. This section should be actually complete. It is a long one!)

[rsokl]

Thanks so much for the careful read through @davidmascharka ! Hugely appreciated