Design vs Testing · both proven

prototype vs tdd

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.

prototype

Build a throwaway prototype to answer a design question. Use when the user wants to sanity-check whether a state model or logic feels right, or explore what a UI should look like.

Category: Design
Source: mattpocock/skills
License: MIT
Proof model: claude-opus-5-5
Brief: “We are designing the order state model for a food delivery app. An order can be placed, accepted by the restaurant, being prepared, ready for pickup, picked up by a courier, and delivered. The customer can cancel until the restaurant starts preparing; the restaurant can cancel at any time before pickup; a cancellation after payment triggers a refund, partial if food was already prepared. We are not sure this logic is right. Build a throwaway prototype as a single HTML page that lets someone on the team drive an order through these states and see where the rules break or get confusing.”
Skill commit: 5beb35b

Without the skillWith prototype

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Without, runWith prototype, run3 independent runs per side, none selected by hand.

Download the with-skill page

tdd

Test-driven development. Use when the user wants to build features or fix bugs test-first, mentions "red-green-refactor", or wants integration tests.

Category: Testing
Source: mattpocock/skills
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: 5beb35b

Without the skillWith tdd

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Without, runWith tdd, run3 independent runs per side, none selected by hand.

Download the with-skill page

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 prototype or alternatives to tdd.