Rather than giving Fable an explicit rule like 'only use automated testing for larger features, don't update and run tests for small copy or design changes,' it's better to tell Fable to use its own judgement about when to write tests.

Testing was the concrete example: instead of hard-coding a rule about when to test, just tell Fable to judge for itself. ✦ AI generated

Cat Wu and Thariq Shihipar · Simon Willison's Weblog · 2026-07-03 · original ↗

The example they gave was testing. You can tell Fable "only use automated testing for larger features, don't update and run tests for small copy or design changes" - but it's better to just tell Fable to use its own judgement when deciding to write tests instead.

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