Two testing skills · both proven

systematic-debugging vs test-driven-development

Both skills were run through Claude twice: once on a fixed brief without the skill, once with it. The briefs differ because each is written for the job the skill claims to do, so compare each skill against its own baseline, then decide which difference matters for your work.

systematic-debugging

Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes

Category: Testing
Source: obra/superpowers · 301,947 stars
License: MIT
Proof model: claude-opus-5-5
Brief: “A Node.js API returns 500 for about 1 in 200 requests to POST /orders. Logs show 'TypeError: Cannot read properties of undefined (reading "id")' at orders.js:48, which reads req.user.id. The route is behind an auth middleware. The failures started after a deploy that added a 30-second cache on the session lookup. Present your diagnosis and fix as a single HTML page: what you checked, in order, the root cause, the code change, and how you would confirm it is fixed.”
Skill commit: bb92a77

test-driven-development

Use when implementing any feature or bugfix, before writing implementation code

Category: Testing
Source: obra/superpowers · 301,947 stars
License: MIT
Proof model: claude-opus-5-5
Brief: “Implement a function that parses a cron expression (the standard five fields) and returns the next run time after a given date, in TypeScript. Present the work as a single HTML page with two columns: the test file on the left and the implementation on the right, each in a code block, with a short note at the top on the order you did things in and anything you decided not to support.”
Skill commit: bb92a77

We don’t pick a winner for you: the pages are the evidence. Both proofs can be repeated with the brief, model and commit shown above. See alternatives to systematic-debugging or alternatives to test-driven-development.