# Unit Test > Write and review xterm.js unit tests with project conventions. Use when editing `*.test.ts` files or when asked for test authoring guidelines. Use when this capability is needed. - Skill: `tomevault-io/unit-test` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/unit-test` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/unit-test/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/unit-test --- # Unit Test Instructions When writing unit tests, follow these rules: - When writing unit tests for addons, always create a real xterm.js instance instead of mocking it. - Prefer `assert.ok` over `assert.notStrictEqual` when checking something is undefined or not. - Avoid comments as most tests should be self-documenting. --- > Source: [xtermjs/xterm.js](https://github.com/xtermjs/xterm.js) — distributed by [TomeVault](https://tomevault.io).