Lean body that defers TDD basics to Beck ('For TDD basics, defer to Kent Beck') and compresses the catalog into a table, a decision tree, a worked example, an anti-patterns table, and a short limitations section — every token earns its place and Claude's competence is assumed.

Gives a concrete 7-step 'How to use', a decision tree that routes symptoms to pattern numbers, and a worked example with executable code ('processOrder(1, { findOrder: () => ({ id: 1 }) })'); the linked reference files contain complete before/after code for each pattern.

The multi-step process is clearly sequenced (numbered 1-7) with a decision tree for routing and a worked example walking route -> open -> move -> test; the test written at the seam acts as the verification checkpoint, and refactoring here is incremental rather than a destructive batch operation.

The body is an overview whose pattern table links to three real, one-level-deep reference files (injection-patterns.md, boundary-adapter-patterns.md, structural-patterns.md), each covering a distinct pattern group with full before/after code — content is appropriately split and clearly signaled.

Lists multiple concrete actions: 'recognizes common testability blockers (singletons / static dependencies, network in constructors, time / random as hidden inputs, deeply nested construction, untestable boundaries) and proposes the refactor that unblocks TDD (extract interface, dependency injection, seam, ports-and-adapters)'.

Answers both what (pattern catalog that recognizes blockers and proposes refactors) and when ('Use as TDD coaching when an engineer is stuck on a class of code') with an explicit trigger clause.

Leads with the natural phrase an engineer would actually say — '"I can\'t write the test first" moments' — and 'when an engineer is stuck on a class of code', giving good coverage of real trigger language.

Explicitly routes three sibling skills to distinct niches ('For a catalog of what-to-test heuristics ... use heuristic-test-design-reference, to label a change\'s shape ... use code-change-shape-classifier, and for conventions on writing the test well ... use test-code-conventions'), giving it a clear niche unlikely to conflict.