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.
npx skills add cosmicstack-labs/mercury-agent-skills --skill testing-strategiesgit clone --depth 1 https://github.com/cosmicstack-labs/mercury-agent-skillsWrote 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.
[](https://agentmods.dev/skills/cosmicstack-labs/mercury-agent-skills/testing-strategies)<a href="https://agentmods.dev/skills/cosmicstack-labs/mercury-agent-skills/testing-strategies"><img src="https://agentmods.dev/badge/skills/cosmicstack-labs/mercury-agent-skills/testing-strategies/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.
<a href="https://agentmods.dev/skills/cosmicstack-labs/mercury-agent-skills/testing-strategies"><img src="https://agentmods.dev/badge/skills/cosmicstack-labs/mercury-agent-skills/testing-strategies.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Data Exfiltration · line 226 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
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 | $0.00027 | $0.04277 |
| Opus 5 | $0.00014 | $0.02139 |
| Sonnet 5 | $0.00005 | $0.00855 |
| Haiku 4.5 | $0.00003 | $0.00428 |
Grade A, and why
testing-strategies 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 6d 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.
How it starts
The opening of the file, as written. The whole thing — 611 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Testing Strategies
A comprehensive approach to testing that gives you confidence your code works correctly — from unit tests to mutation testing.
Core Principles
1. Test Behavior, Not Implementation
Your tests should specify what the code does, not how it does it. Tests that pass after a refactor (with the same behavior) are good tests. Tests that break after a refactor (with the same behavior) are brittle tests.
2. The Test Pyramid Is a Guideline, Not a Rule
Write many fast unit tests, some integration tests, and a few end-to-end tests. But adjust ratios based on your context: a data pipeline needs more integration tests; a UI component needs more visual regression tests.
3. Tests Are Code — Treat Them That Way
Tests need the same care as production code: clean naming, DRY helpers, proper abstractions. Test code that's hard to maintain leads to tests that get deleted.
4. Confidence Is the Goal
Coverage numbers are a proxy metric. A codebase with 80% coverage and excellent tests is better than one with 100% coverage and shallow tests. Test the things that scare you.
Testing Maturity Model
| Level | Unit Tests | Integration Tests | CI Integration | Quality Gates |
|---|---|---|---|---|
| 1: None | No tests | No tests | No CI | None |
| 2: Skeleton | Some critical paths | Happy-path smoke tests | Tests run manually | None |
| 3: Standard | >60% coverage | >80% of API endpoints | Tests run on every PR | Coverage check: >60% |
| 4: Systematic | >80% coverage | Contract tests + DB tests | CI fails on test failure | Coverage + mutation score >70% |
| 5: Excellence | Property-based + mutation | Consumer-driven contracts | Test parallelization, flaky test detection | Mutation score >85%, flaky tests auto-retry |
Target: Level 3+ for production services. Level 4+ for critical systems.
Actionable Guidance
Unit Testing Patterns
The AAA Pattern (Arrange, Act, Assert)
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.
- 6d ago First seen · 611 lines · 27 tokens per session scan A 2f18778f7fa2
testing-strategies is a skill published in the GitHub repository cosmicstack-labs/mercury-agent-skills (470 stars, last pushed 16d ago), licensed MIT. It adds 27 tokens to every session and 4,277 once invoked, about $0.0001 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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