The body is well-organized but carries tightening room: repeated per-language tool lists, embedded Fowler quotes, and 'Canonical source' attribution prose that pad tokens beyond what a lean reference needs, matching 'mostly efficient but could be tightened'.

It provides a need-to-pattern selection table, per-pattern 'When to use' guidance, explicit hand-off routing, and complete runnable code examples (TypeScript builder, Ruby FactoryBot), giving copy-paste-ready and decision-ready guidance.

For a single-decision catalog skill the path is unambiguous: selection guide routes the need to a pattern, anti-patterns guard the choice, and hand-off targets sequence where to go next, satisfying the simple-skill allowance for a clear single action.

All references are one level deep (external URLs and named sibling skills) with no nested drill-downs, the skill explicitly defers operational details to golden-file-conventions and per-language skills, and content is cleanly sectioned, matching the well-organized-sections allowance for skills with no bundle files.

Names multiple concrete actions and a concrete catalog (Test Data Builder, Factory with traits and associations, Object Mother, Fixture composition, Snapshot, Production-Data Anonymisation) plus 'choosing' and 'auditing' actions, matching the score-3 anchor for multiple specific concrete actions.

It explicitly states what the skill is (an architecture-tier reference catalog for choosing which pattern) and when to use it via the explicit 'Use when...' clause, satisfying both the what and the when at the score-3 level.

The 'Use when choosing a test-data construction pattern for a new suite, or auditing an existing suite whose fixtures have drifted into shared mutable state' clause supplies natural phrases a user would say, with strong coverage of test-data/fixtures vocabulary; not merely jargon.

It carves a clear niche ('architecture-tier reference for choosing which pattern before reaching for the tool') and explicitly distinguishes it from named sibling skills (factory-bot-data, faker-data, mimesis-data, bogus-data, golden-file-conventions), making mis-triggering unlikely.