testing

testing is a skill for Claude Code, Codex from liza-mas/liza. It costs 4 tokens per session (599 once invoked), scanned A, original, Apache-2.0.

A testing guide built around the idea that tests should expose bugs and preserve intended behaviour.

In plain words
What is it for?
Use it when analysing test results, checking code and test logic independently, and deciding when a test may be changed with approval.
Why use it?
It helps developers interpret failing tests, avoid changing expectations just to make tests pass, and investigate whether the code or the test is wrong.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/liza-mas/liza/testing
Any agent
npx skills add liza-mas/liza --skill testing
Clone the repo
git clone --depth 1 https://github.com/liza-mas/liza

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.

agentmods badge for testing

README.md
[![agentmods](https://agentmods.dev/badge/skills/liza-mas/liza/testing.svg)](https://agentmods.dev/skills/liza-mas/liza/testing)
Your own site
<a href="https://agentmods.dev/skills/liza-mas/liza/testing"><img src="https://agentmods.dev/badge/skills/liza-mas/liza/testing.svg" alt="Measured on agentmods" height="20"></a>
Per session 4 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 599 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00004 $0.00599
Opus 5 $0.00002 $0.00300
Sonnet 5 $0.00001 $0.00120
Haiku 4.5 $0.00000 $0.00060

Measured 5d ago against content hash 3fd98b1e126f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

testing 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 5d 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/testing/SKILL.md · 74 lines

How it starts

The opening of the file, as written. The whole thing — 74 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Tests are the immune system — they reject bugs, not document them.

Test Truth Table

Code Test Interpretation
Working Green Good
Buggy Red Good (bug exposed)
Working Red Wrong expectations
Buggy Green DANGEROUS
Unknown Red STOP — use Analysis Framework below

ANTI-PATTERN: The most dangerous instinct is to "fix" failing tests by accepting whatever source currently does.

When Tests Fail

Ask for context:

  • Is the code in production? Not a guarantee of correctness, yet to consider
  • Is the test much more recent than the source code? Could explain wrong expectations

Default heuristic: Tests encode intent; assume the test is correct until evidence suggests otherwise. Source drifts; tests usually don't drift without reason.

Analysis Framework:

  1. Examine both logics independently
  2. Consider system design: method contract, error patterns
  3. Identify sounder logic given context
  4. When uncertain, ask user
  5. Type hints may be wrong — verify actual runtime behavior before trusting signatures

Test Modification

FORBIDDEN without approval:

  • Changing assertions to match buggy behavior
  • Weakening expectations
  • Adding exception handlers to mask failures

Allowed: Fresh repro tests capturing current failure (existing tests untouched).

Writing Tests

Quality Standards:

  • Deterministic, behavioral testing over type checking
  • Exception testing with message validation: pytest.raises(ValueError, match="...")
  • Systematic edge cases: None, boundaries, dates
  • Branch coverage: success and failure paths

Assertion Strength: Would this assertion pass for a broken implementation? If yes (tautology, type-only, existence-only, shape-only), strengthen it.

Mocking Discipline: Test the code, not the scaffolding. Heavy mock setup suggests you're testing assumptions about dependencies, not behavior. Mock external boundaries (APIs, DBs, filesystems), not internal logic.

Read the full file on GitHub · 74 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.

  1. 5d ago First seen · 74 lines · 4 tokens per session scan A 3fd98b1e126f

Subscribe to this mod's changes

testing is a skill published in the GitHub repository liza-mas/liza (364 stars, last pushed 3d ago), licensed Apache-2.0. It adds 4 tokens to every session and 599 once invoked, about $0.0000 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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