April 09, 2016

Hypothesis with David MacIver

47 minutes

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Summary

Writing tests is important for the stability of our projects and our confidence when making changes. One issue that we must all contend with when crafting these tests is whether or not we are properly exercising all of the edge cases. Property based testing is a method that attempts to find all of those edge cases by generating randomized inputs to your functions until a failing combination is found. This approach has been popularized by libraries such as Quickcheck in Haskell, but now Python has an offering in this space in the form of Hypothesis. This week, the creator and maintainer of Hypothesis, David MacIver, joins us to tell us about his work on it and how it works to improve our confidence in the stability of our code.

Brief Introduction

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Your hosts as usual are Tobias Macey and Chris Patti

Today we are interviewing David MacIver about the Hypothesis project which is an advanced Quickcheck implementation for Python.

Interview with David MacIver

Introductions

How did you get introduced to Python? – Chris

Can you provide some background on what Quickcheck is and what inspired you to write an implementation in Python? – Tobias

Are there any ways in which Hypothesis improves on the original design of Quickcheck? – Tobias

Can you walk us through the execution of a simple Hypothesis test to give our listeners a better sense for what Hypothesis does? – Chris

Have you had trouble getting people to use Hypothesis? How has adoption been? – David

What does this sort of testing get you that conventional testing doesn’t? – David

Why do you think this sort of testing hasn’t caught on in the Python world before? – David

Are there any facilities of the Python language that make your job easier? Are there aspects of the language that make this style of testing more difficult? – Tobias

What are some of the design challenges that you have been presented with while working on Hypothesis and how did you overcome them? – Tobias

Given that testing is an important part of the development process for ensuring the reliability and correctness of the system under test, how do you make sure that Hypothesis doesn’t introduce uncertainty into this step? – Tobias

Given the sophisticated nature of the internals of Hypothesis, do you find it difficult to attract contributors to the project? – Tobias

A few months ago you went through some public burnout with regards to open source and Hypothesis in particular, but circumstances have brought you back to it with a more focused plan for making it sustainable. Can you provide some background and detail about your experiences and reasoning? – Tobias

What’s next for Hypothesis? – Chris

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The intro and outro music is from Requiem for a Fish The Freak Fandango Orchestra / CC BY-SA

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