https://www.hillelwayne.com/tags/hypothesis/ Recent content in Hypothesis on Hillel Wayne Hugo -- gohugo.io en-us Fri, 19 Jun 2020 00:00:00 +0000 https://www.hillelwayne.com/post/property-testing-complex-inputs/ Fri, 19 Jun 2020 00:00:00 +0000 https://www.hillelwayne.com/post/property-testing-complex-inputs/ This was originally written as a tutorial for Hypothesis and will eventually be reproduced there, but it might still be useful for people using other property-testing libraries. This essay assumes some familiarity with Hypothesis. If you haven’t used it, a better introduction is here. Once you learn the basics, there are two hard parts to writing property-based tests: What are good properties to test? How do I generate complex inputs? https://www.hillelwayne.com/post/contract-examples/ Mon, 08 Apr 2019 00:00:00 +0000 https://www.hillelwayne.com/post/contract-examples/ A while back I was ranting about APLs and included this python code to get the mode of a list: def mode(l): max = None count = {} for x in l: if x not in count: count[x] = 0 count[x] += 1 if not max or count[x] > count[max]: max = x return max There’s a bug in it. Do you see it? If not, try running it on the list [0, 0, 1]: https://www.hillelwayne.com/post/pbt-contracts/ Sun, 17 Dec 2017 00:00:00 +0000 https://www.hillelwayne.com/post/pbt-contracts/ I’m a pretty big fan of contracts and property-based testing. While they’re both powerful, they do have tradeoffs: Contracts are simple and allow for complex conditionals, but you need to test them over a wide space to confirm them. Property-Based Testing can test your code over a very wide search space, but you have to come up with good generators and invariants. Maybe they complement each other: “your code doesn’t violate any contracts” counts as a PBT invariant. https://www.hillelwayne.com/post/hypothesis-oracles/ Fri, 21 Jul 2017 09:00:00 -0500 https://www.hillelwayne.com/post/hypothesis-oracles/ This post is about the Hypothesis testing library. If you’re unfamiliar with it, check it out! Property tests are a fantastic addition to your testing suite. All examples use pytest. Imagine we’ve written a bubblesort: def bubblesort(l: List[int]) -> List[int]: # blah blah blah What are some of the properties we could test? We could check that the input has the same length as the output: from hypothesis import given from hypothesis.