fast-check VS volkswagen

Libraries like JSVerify or Fast-Check offer essential tools to facilitate property-based testing.

Strong agree!

For JavaScript, I suggest folks check out fast-check [0] and this introduction to property-based testing that uses fast-check [1].

This is broadly useful, but one specific place I've found it helpful was to check redux reducers against generated lists of actions to find unchecked edge cases and data assumptions.

[0] https://github.com/dubzzz/fast-check

Brilliant, this is a massive improvement. Previously I was fumbling around in https://github.com/dubzzz/fast-check/tree/main/packages/fast-check/documentation for info.

There's a library for exactly that: FastCheck.

It makes @fast-check/jest, the best option to integrate Jest and fast-check, as it provides an abstraction over both to ease their mutual integration.

The closest that I know of (and I have not used this) is zod-fast-check. It generates fast-check “arbitraries” (test data generators) for property-based testing based on zod schemas. Of course, this requires that you use zod to define your types, which has some downsides. Fortunately there is another tool, ts-to-zod, (which I also have not used) which will codegen zod schemas based on TS type definitions. If you thread these four libraries together you should end up with the ability to write random tests on generated data with very little overhead. In theory.

For something like this, I might break out fast-check for testing. It’s good at generating a wide range of values for a given type, and could help you get good test coverage without having to hand-author a lot of repetitive error inputs.

Or, more practically, they may be using pytest-vw (https://github.com/auchenberg/volkswagen).

import volkswagen

#1: Please don’t use “win” as an abbreviation for Microsoft Windows in GNU software or documentation. [...] calling something a “win” is a form of praise. You’re free to praise Microsoft Windows on your own if you want, but please don’t do so in GNU packages. | 60 comments #2: 'volkswagen' detects when your tests are being run in a CI server and makes them pass | 19 comments #3: In 2001, I said "I use Linux" to RMS's face, and interrupted his usual rant by explaining that the userspace was not GNU, so I did mean "Linux". He was speechless for the best 5 seconds of my life. | 34 comments

So they need https://www.npmjs.com/package/volkswagen

Along with no tests, you should probably remove any linting tools. If the code doesn't still have to work maybe consider removing ci/cd, or just https://github.com/auchenberg/volkswagen

Best repo on GitHub.