Testing vs Docs & Writing · both proven

test-driven-development vs writing-plans

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. They are in different categories, so this is a choice of job, not a head-to-head on the same job.

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

writing-plans

Use when you have a spec or requirements for a multi-step task, before touching code

Category: Docs & Writing
Source: obra/superpowers · 301,947 stars
License: MIT
Proof model: claude-opus-5-5
Brief: “Write the implementation plan for adding team accounts to a solo-user invoicing SaaS (Next.js, Postgres, Stripe): users must be able to create a team, invite members by email, assign owner or member roles, and share clients and invoices within the team, with billing moving from the user to the team. Present the plan as a single HTML page.”
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 test-driven-development or alternatives to writing-plans.