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test-driven-development

Implements a feature or bug fix test-first: write one failing test, run it and watch it fail, write the minimal code to pass, then refactor with the tests green. Use when a change alters code behavior: a new feature, a bug fix, or a behavior change, whether the request comes alone or through delivery-flow.

69

Quality

87%

Does it follow best practices?

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SKILL.md
Quality
Evals
Security

Quality

Content

81%Weight 40%Scale 1-5

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

A highly actionable, well-sequenced TDD skill with explicit verification gates, error-recovery loops, and a clean one-level reference split. Its main cost is token weight: motivational rhetoric and duplicated enforcement sections could be consolidated without losing instructional value.

Suggestions

Merge the Red Flags list into the Common Rationalizations table (or vice versa) — the two sections enumerate nearly the same anti-patterns twice; one combined table would cut ~25 lines.

Collapse "Overview", "The Iron Law", and "Final Rule" into a single statement of the core rule; all three restate "no production code without a failing test first".

Consider moving the extended Common Rationalizations rebuttals into references/writing-good-tests.md (or a dedicated reference) and keeping only the top few excuses inline, reducing SKILL.md toward an overview-plus-procedure document.

DimensionReasoningScore

Conciseness

The procedural core is tight and imperative, but the body carries clear redundancy: the Red Flags list repeats the Common Rationalizations table, "Final Rule" restates "The Iron Law", "Overview" restates "Before you edit any production file", and the dot graph plus aphorisms add tokens without adding instruction. Not 2 because no section explains basic concepts Claude already lacks.

3 / 5

Actionability

Fully executable guidance throughout: complete good/bad TypeScript test and implementation examples, concrete commands (`npm test path/to/test.test.ts`), and a worked bug-fix example covering every phase from RED through REFACTOR. Common cases are covered copy-paste ready.

5 / 5

Workflow Clarity

The red-green-refactor sequence has explicit MANDATORY verification checkpoints, feedback loops for error recovery ("Test errors? Fix error, re-run until it fails correctly"; "Test fails? Fix code, not test"), a verification checklist, and a recovery path if production code was edited first. Matches the anchor with validation steps, feedback loops, and a checklist.

5 / 5

Progressive Disclosure

The single reference (references/writing-good-tests.md) is one level deep, clearly signaled, and summarized inline with its key rules, and the file exists in the bundle. Not 5 because the ~320-line body inlines long rationalization and red-flag content that could be split out, leaving SKILL.md heavier than a clear overview.

4 / 5

Total

17

/

20

Passed

Description

88%Weight 40%Scale 1-5

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

A strong description that states a concrete, multi-step capability and an explicit trigger clause with specific conditions. Its only weaknesses are missing common synonyms (TDD, refactoring, unit tests) and slightly broad triggers that could overlap with adjacent coding skills.

DimensionReasoningScore

Specificity

The description enumerates the complete concrete workflow — "write one failing test, run it and watch it fail, write the minimal code to pass, then refactor with the tests green" — giving comprehensive, specific coverage of what the skill does rather than generic claims.

5 / 5

Completeness

Both questions are explicitly answered: the "what" is the four-step test-first workflow, and the "when" is a concrete "Use when a change alters code behavior" clause listing specific triggers. Not 4 because the when-clause lists concrete trigger phrases rather than being merely adequate.

5 / 5

Trigger Term Quality

Natural phrases like "a new feature, a bug fix, or a behavior change" are present and would be said by users, but common synonyms such as "refactoring", "unit tests", or "TDD" itself are missing, so coverage is good rather than comprehensive.

4 / 5

Distinctiveness Conflict Risk

The test-first process niche is clear and unlikely to trigger for unrelated skills, but the triggers (any feature, bug fix, or behavior change) are broad and could overlap with general implementation or code-review skills. Not 5 because conflict risk is minor rather than minimal.

4 / 5

Total

18

/

20

Passed

Validation

100%

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 16 / 16 Passed

Validation for skill structure

No warnings or errors.

Repository

tesslio/tessl-eval-demo

Path

02-mutation/versions/checklist-first/sdlc-implementation/skills/test-driven-development/SKILL.md

Reviewed

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