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 agentmods add skills/alleneubank/claude-code/testing-best-practicesnpx skills add alleneubank/claude-code --skill testing-best-practicesgit clone --depth 1 https://github.com/alleneubank/claude-codeWrote 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/alleneubank/claude-code/testing-best-practices)<a href="https://agentmods.dev/skills/alleneubank/claude-code/testing-best-practices"><img src="https://agentmods.dev/badge/skills/alleneubank/claude-code/testing-best-practices.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00034 | $0.01065 |
| Opus 5 | $0.00017 | $0.00532 |
| Sonnet 5 | $0.00007 | $0.00213 |
| Haiku 4.5 | $0.00003 | $0.00106 |
Grade A, and why
testing-best-practices 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 4d 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- testing-best-practices — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 109 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test layering policy
Unit tests
Purpose: verify individual functions and invariants in isolation.
- Data-driven: parameterized tables covering happy path, boundary, error, and edge cases.
- Property-based: fuzz invariants that must hold across all inputs (e.g., idempotency, sort stability, roundtrip serialization).
- Derive cases from the module's public API surface: input types/constraints, output shape, error modes, invariants.
Integration / contract tests
Purpose: verify interactions between components and external services.
- API envelope: request/response shape, status codes, content types, pagination.
- Error contract: error codes, error shapes, rate limiting, retries.
- Auth and scoping: token validation, role-based access, tenant isolation.
- Eventual consistency: verify convergence within bounded time; poll rather than sleep.
- Reuse auth state across tests where possible; avoid redundant login flows.
E2E tests
Purpose: verify real user workflows through the full stack.
- No mocks; exercise real services, databases, and APIs.
- Happy-path workflows only; save edge cases for lower layers.
- State-tolerant: never assume a clean slate; tolerate and work with prior state.
- Idempotent: safe to run repeatedly without cleanup between runs.
- Flow-oriented: validate real data paths end-to-end rather than isolated assertions.
Hard rules
- Never invent signatures, source locations, or line numbers. Only reference what you have read from the codebase.
- No fabricated fixtures. Derive test data from actual schemas, types, or seed data in the repo.
- No test-only hacks in product code. No
if (process.env.TEST)branches, no test-specific exports, no test backdoors. - E2E must not rely on clean slate. Tests must tolerate pre-existing data, prior test runs, and shared environments.
Execution guidance
Preflight checks (before e2e)
- Verify the target environment is reachable (health endpoint, ping).
- Confirm required services are running (database, API, auth provider).
- Validate test user / credentials exist and are functional.
- Check for leftover state that could cause false failures; log it, do not fail on it.
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.
- 4d ago First seen · 109 lines · 34 tokens per session scan A ad157a0d358c
testing-best-practices is a skill published in the GitHub repository alleneubank/claude-code (52 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 34 tokens to every session and 1,065 once invoked, about $0.0002 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 2026-08-30.
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