John Hughes - Testing the Hard Stuff and Staying Sane
Why Hacker News recommends it
Recommended as the best introduction to property-based testing and cited for its examples of bugs found in the CAN standard.
What it is
John Hughes, co-creator of QuickCheck, talks about property-based testing of hard systems. He shows production examples where it found very low-level bugs, including issues in the CAN bus standard.
Recommended by 4 HN commenters across 4 different months, 2016 to 2026.
What Hacker News said
Strong rec Naomarik · 2016-12 · on “QuickCheck: A Lightweight Tool for Random Testing of Haskell Programs (2000) [pdf]”
I'd recommend watching this [this video] to see how powerful this can be. I've just discovered generative testing due to clojure.spec. Describing specs for your data works not only to help validate data structures but can be plugged in as properties for generative testing. After the "aha" moment it was followed by a feeling that I've wasted so much time writing specs just to validate data structures and writing specs just to see if my functions are working as they should. This is one of the things I wish was obvious in my learning track right after vim/emacs will help you code faster.
Recommends dllthomas · 2022-10 · on “Show HN: IHP v1.0 – Batteries-included web framework built on Haskell and Nix”
While of course Haskell has more normal testing infrastructure available (eg. [LINK] ), my favorite bit of Haskell testing is QuickCheck, which IIUC started life in Haskell and has been reimplemented in other languages with various degrees of effectiveness and various degrees of connection to the original project. John Hughes (not the filmmaker) gives a great talk about it: [this video]
Recommends robertfw · 2025-11 · on “Hypothesis: Property-Based Testing for Python”
I feel like this talk by John Hughes showed that there is real value in this approach with production systems of varying levels of complexity, with two different examples of using the approach to find very low level bugs that you'd never think to test for in traditional approaches. [this video]
Recommends devin · 2026-04 · on “Mysteries of Dropbox: Property-Based Testing of a Distributed Sync Service [pdf]”
One of the authors, John Hughes did a talk on property-based testing at Clojure West some number of years back. Worth a watch if you're interested: [this video]
Cites illiarian · 2023-04 · on “Car Thieves Using Tech Disguised Inside Old Nokia Phones and Bluetooth Speakers”
> CAN bus is a brilliant thing for car diagnostics and modification but with every good system normally has a sword of damocles. There are over 100 issues (aka bugs) in the spec though. Uncovered by these guys: [this video] (starting at 19:10, includes examples)
Cites troupo · 2023-11 · on “Voters Overwhelmingly Pass Car Right to Repair Law in Maine”
Possibly due to amount of data coming from various sensors and systems. BTW, CAN standard is riddled with bugs: [this video] at 26:18