What is test-strategy?

A testing-planning tool that decides what parts of a project to test, which testing levels to use, and how to prioritize them before test code is written.

Use it when starting a project or module, improving weak test coverage, choosing between testing levels, or planning tests after a production incident.

It helps avoid slow, fragile, or misleading test suites that check the wrong things. Unit tests check small pieces, integration tests check components working together, and end-to-end tests check complete user flows.

test-strategy — Skill for Claude Code and Codex by JakubMikolajek

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add JakubMikolajek/codex-skills-collection --skill test-strategy

Clone the repo

git clone --depth 1 https://github.com/JakubMikolajek/codex-skills-collection

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/jakubmikolajek/codex-skills-collection/test-strategy/github.svg)](https://agentmods.dev/skills/jakubmikolajek/codex-skills-collection/test-strategy)

Your own site

<a href="https://agentmods.dev/skills/jakubmikolajek/codex-skills-collection/test-strategy"><img src="https://agentmods.dev/badge/skills/jakubmikolajek/codex-skills-collection/test-strategy/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/jakubmikolajek/codex-skills-collection/test-strategy"><img src="https://agentmods.dev/badge/skills/jakubmikolajek/codex-skills-collection/test-strategy.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 75 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,016 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00075	$0.02016
Opus 5	$0.00037	$0.01008
Sonnet 5	$0.00015	$0.00403
Haiku 4.5	$0.00007	$0.00202

Measured 9d ago against content hash 994242d52d2b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

test-strategy scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/test-strategy/SKILL.md · 225 lines

How it starts

The opening of the file, as written. The whole thing — 225 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Test Strategy

This skill sits one level above the testing implementation skills (unit-testing, e2e-testing, python-testing). It answers the question "what should we test and how" before any test code is written.

Use this skill when starting a new project, onboarding a new module with no tests, or when the current test suite is fragile, slow, or missing coverage in the wrong places.

When to Use

Starting a new project or module with no existing tests
Existing test suite is slow, flaky, or producing false confidence
Team is debating whether to write unit tests, integration tests, or E2E tests for a feature
/plan output includes a testing phase but no test strategy has been defined
Implementation-gap-analysis reveals test coverage exists but tests are testing the wrong things
After a production incident where no test caught the regression

When NOT to Use

Test strategy already exists and is documented — go directly to unit-testing, e2e-testing, or python-testing
Task is adding one test to an established, well-structured suite — no strategy needed
User explicitly says "I know what tests I need, help me write them"

Core Principles

Test at the Right Level

The most common testing mistake is testing at the wrong level of the pyramid. This skill forces an explicit decision before any test is written.

         /\
        /  \   E2E (few, slow, high confidence on full flows)
       /----\
      /      \  Integration (moderate, test boundaries and contracts)
     /--------\
    /          \  Unit (many, fast, test logic in isolation)
   /____________\

Rule: Push tests as low in the pyramid as they can go while still catching real bugs. Do not write E2E tests for logic that can be verified at unit level. Do not write unit tests for behavior that only matters at integration level.

Confidence Over Coverage

100% line coverage with tests that mock everything is worse than 60% coverage with tests that catch real regressions. This skill prioritises confidence — the probability that a failing test means something is actually broken — over raw coverage numbers.

Read the full file on GitHub · 225 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

9d ago First seen · 225 lines · 75 tokens per session scan A 994242d52d2b

Subscribe to this mod's changes

test-strategy is a skill published in the GitHub repository JakubMikolajek/codex-skills-collection (5 stars, last pushed 7d ago), licensed MIT. It adds 75 tokens to every session and 2,016 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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test-strategy