writing-tests

Gates whether a new test should exist and forces it to be efficient, protecting CI from low-value test bloat. Use before any change to what a pytest, Jest, or Playwright test asserts or sets up, down to one fixture or one assertion added to an existing block. Front-loads the value bar (every test must catch a realistic regression no existing test already catches; extend the nearest existing test before writing a new standalone one; test behavior through the public interface, not implementation details; collapse near-duplicates into parameterized cases) and the efficiency bar (deterministic, isolated, fast; pick the cheapest test level; Django TestCase over TransactionTestCase; no sleeps, no real network; no time bombs from absolute dates left to age against the real clock; no database a test never uses). Includes a "don't write it" decision tree. For fixing an existing flaky test use `/fixing-flaky-tests`; after this gate says a Playwright test is warranted, use `/playwright-test` for mechanics.

Quality

76%

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tessl review fix ./.agents/skills/writing-tests/SKILL.md

Quality

Content

63%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 rich, opinionated, project-specific testing gate with strong actionable examples and a clear decision sequence. Its main weaknesses are verbosity in several expository passages and progressive-disclosure gaps where heavy detail is inlined and referenced bundle files are missing.

Suggestions

Tighten the discursive prose in the 'Always — determinism and isolation' section into crisper bullets — keep the project-specific facts but cut the narrative padding around clocks and mtimes.

Move the DRF input-validation deep-dive and the determinism/isolation rules into reference files under references/ (which the body already cites) so SKILL.md stays a lean overview with one-level-deep pointers.

Add the referenced files (references/mistakes-we-make.md, references/database-free-test-classes.md) to the bundle so the signaled links resolve, or remove the links if the files are not bundled.

Dimension	Reasoning	Score
Conciseness	Most of the content is genuinely project-specific guidance that earns its place, but several passages are discursively padded — e.g. the delta-rs mtime explanation and the wall-clock-budget narrative — that could be tightened into crisper bullets without losing clarity.	3 / 5
Actionability	It gives concrete, executable guidance — a copy-paste SimpleTestCase serializer example, an exact grep TTL command, specific helper paths (posthog/test/persons.py) and library calls (time_machine.travel with tick=False, jest.useFakeTimers) — with only minor gaps where guidance stays at the principle level.	4 / 5
Workflow Clarity	The gate is a clearly sequenced decision procedure — two questions, the five no's, pyramid weighting, then the PR justification checkpoint ('If you can't write that line, you've found a test that shouldn't be in the PR') — with most checkpoints present, though it lacks explicit error-recovery feedback loops.	4 / 5
Progressive Disclosure	Section structure and markdown reference links are clearly signaled, but the body inlines substantial reference-grade detail (the entire 'Always — determinism and isolation' section, the DRF validation deep-dive) and the referenced files references/mistakes-we-make.md and references/database-free-test-classes.md are not present in the bundle, so the signaled references do not resolve.	3 / 5
	Total	14 / 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, concrete description that clearly states both what the skill does and when to use it, with explicit routing to sibling skills. It is somewhat verbose for a description field and could enumerate a few more natural trigger synonyms, but it is comprehensive and specific.

Dimension	Reasoning	Score
Specificity	The description lists multiple concrete, specific actions across both bars — 'extend the nearest existing test before writing a new standalone one', 'collapse near-duplicates into parameterized cases', 'Django TestCase over TransactionTestCase', 'no sleeps, no real network', 'no time bombs from absolute dates' — giving comprehensive coverage of the skill's behavior.	5 / 5
Completeness	It explicitly answers both what ('Gates whether a new test should exist and forces it to be efficient...') and when ('Use before any change to what a pytest, Jest, or Playwright test asserts or sets up, down to one fixture or one assertion') with concrete trigger phrases.	5 / 5
Trigger Term Quality	It names the natural framework triggers a user would say ('pytest, Jest, or Playwright test', 'fixture', 'assertion') but omits common synonyms like 'unit test', 'integration test', or 'spec' that would round out coverage to a 5.	4 / 5
Distinctiveness Conflict Risk	The skill has a clear niche — gating new-test creation — and explicitly routes sibling concerns to '/fixing-flaky-tests' and '/playwright-test', but it still operates in a testing domain with closely related skills, leaving minor overlap risk.	4 / 5
	Total	18 / 20 Passed

Validation

87%

Warnings & errors only

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

Validation — 14 / 16 Passed

Validation for skill structure

Criteria	Description	Result
relative_links	Relative link issues: 3 missing, 2 suspicious	Warning
referenced_paths_exist	Referenced path issues: 5 missing	Warning

	Total	14 / 16 Passed

Repository: PostHog/posthog
Path: .agents/skills/writing-tests/SKILL.md
Commit: 130f3a1

Reviewed: 9 days ago

Table of Contents

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