testing

A testing guide for writing and reviewing unit, integration, and end-to-end tests. Unit tests check small pieces of logic, integration tests check parts working together, and end-to-end tests check complete user journeys.

In plain words
What is it for?
Use it to decide what tests to write, add regression tests after fixes, preserve coverage during refactoring, and audit a project's testing quality.
Why use it?
It provides a consistent way to test new features, bug fixes, refactors, and overall coverage. Its Testing Trophy approach emphasizes integration tests while still using fast checks and a small number of key end-to-end tests.

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/getlytos/lytos-cli/testing
Any agent
npx skills add getlytos/lytos-cli --skill testing
Clone the repo
git clone --depth 1 https://github.com/getlytos/lytos-cli

Made for: Claude Code, Codex.

Per session 59 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,111 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 $0.00059 $0.03111
Opus 5 $0.00030 $0.01555
Sonnet 5 $0.00012 $0.00622
Haiku 4.5 $0.00006 $0.00311

Measured 2d ago against content hash 7271b7dcb4ac, 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 2d 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.

.lytos/skills/testing/SKILL.md · 416 lines

How it starts

The opening of the file, as written. The whole thing — 416 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill — Testing

This skill defines how to write tests on a project using Lytos. It covers unit tests and end-to-end tests. An agent loaded with this skill knows what to test, how to structure tests, and what coverage criteria to meet.


When to invoke this skill

  • After writing a new feature
  • After a fix — the test must prove the bug won't come back
  • During a refactoring — existing tests must continue to pass
  • During a quality audit — check overall coverage

Testing strategy

Follow the Testing Trophy model (Kent C. Dodds): the highest return on investment comes from integration tests, not unit tests.

        ╱╲          E2E — few, critical journeys only
       ╱  ╲
      ╱────╲
     ╱      ╲       Integration — the bulk of your tests
    ╱        ╲
   ╱──────────╲
  ╱            ╲    Unit — fast, focused, isolated logic
 ╱──────────────╲
╱________________╲  Static analysis — linting, type checking, formatting
Layer Volume What it catches
Static analysis Runs on every save/commit Typos, type errors, style drift
Unit tests Many, fast Logic errors in pure functions
Integration tests Most of your tests Broken contracts between modules, DB queries, API routes
E2E tests Few, slow Critical user journeys broken across the full stack

Write more integration tests than unit tests. Reserve E2E for the journeys where a failure means lost revenue or data.


Unit tests

Principles

  • A unit test tests one single thing
  • It is independent — does not depend on execution order or another test
  • It is fast — no network calls, no database (use mocks)
  • It is deterministic — the same input always gives the same result

Test file structure

tests/
├── unit/
│   ├── [module]/
│   │   └── [module].test.*    <- depends on the project language
│   └── ...
└── e2e/
    ├── [feature].spec.*       <- end-to-end tests
    └── ...

Read the full file on GitHub · 416 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. 2d ago First seen · 416 lines · 59 tokens per session scan A 7271b7dcb4ac

Subscribe to this mod's changes

testing is a skill published in the GitHub repository getlytos/lytos-cli (2 stars, last pushed 2d ago), licensed MIT. It adds 59 tokens to every session and 3,111 once invoked, about $0.0003 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 2026-08-31.