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A Library with no Code

Exercises Jan 12, 2026

In the Interesting Testing series, and Workroom PlayTime 044

Drew Breunig proposes a software library expressed as tests, and a prompt.

Exercise

We'll read the short article – read it now if you've come here before the workshop. Then, we'll talk about it, using the library and the examples to answer questions and think more concretely.

Sources

Article

A Software Library with No Code
Do we still need libraries of 3rd party code when AI agents are this good?

Library

GitHub - dbreunig/whenwords: A relative time formatting library, with no code.
A relative time formatting library, with no code. Contribute to dbreunig/whenwords development by creating an account on GitHub.

Examples

GitHub - dbreunig/whenwords-examples
Contribute to dbreunig/whenwords-examples development by creating an account on GitHub.

Thoughts

Similar to testing for pure functions

UTC doesn't have daylight savings – if we needed daylight savings, we'd need a location and a lookup.

I ported JustHTML from Python to JavaScript with Codex CLI and GPT-5.2 in 4.5 hours
I wrote about JustHTML yesterday—Emil Stenström’s project to build a new standards compliant HTML5 parser in pure Python code using coding agents running against the comprehensive html5lib-tests testing library. Last …

Tags

James Lyndsay

Getting better at software testing. Singing in Bulgarian. Staying in. Going out. Listening. Talking. Writing. Making.