Automated summary

Provides patterns for unit testing including Vitest configuration, Testing Library component testing, MSW for HTTP mocking, parametrized tests, and async testing.

Strengths

Emphasizes testing behavior over implementation
Recommends MSW over jest.mock for network level mocking
Provides ready-to-use references for common testing scenarios
Covers both business logic and UI component testing

Limitations

Assumes familiarity with basic testing concepts
Examples may not cover every edge case
Limited to JavaScript/TypeScript ecosystem

When to use it

Use when setting up a new testing infrastructure or writing unit/component tests for a JavaScript/TypeScript project.

When not to use it

Do not use for end-to-end testing or integration tests that require full system interaction.

Security analysis

Safe

Quality score90/100

The skill defines unit testing patterns and only uses read-only tools (Read, Grep, Glob). There are no destructive actions, code execution, or data exfiltration.

No concerns found

How this analysis is made

Examples

Set up Vitest with coverage

Set up Vitest with v8 coverage for my React project.

Write parametrized tests for a pure function

Write a unit test for a pure function that calculates discounts using parametrized tests.

Mock HTTP request with MSW for component test

Mock an HTTP GET request using MSW for a component test.

name: unit-testing description: | Unit testing patterns: Vitest config with v8 coverage, Testing Library behavior testing, MSW for HTTP mocking (vs jest.mock), it.each parametrized tests, spies vs mocks vs stubs, testing async code, snapshot testing guidelines. Use when writing unit and component tests. allowed-tools: Read, Grep, Glob

Unit Testing Patterns

Name: Unit Testing Patterns
Author: Skills Guide Bot

When to use

Setting up Vitest or Jest for a new project
Writing unit tests for business logic
Component testing with Testing Library
Mocking HTTP requests with MSW
Parametrized tests with it.each

Core principles

Test behavior, not implementation — what does it return/do, not how
MSW over jest.mock — mock at network level, not module level
One assertion per test — single reason to fail per test
Arrange-Act-Assert — consistent structure in every test
No test interdependence — each test must run independently

References available

references/vitest-config.md — globals, environment, coverage thresholds, thread pool, MSW setup
references/business-logic-testing.md — pure function tests, AAA pattern, it.each parametrized tests
references/msw-http-mocking.md — handlers setup, server lifecycle, per-test handler overrides
references/async-testing.md — await patterns, rejected promise assertions, try/catch error checks
references/testing-library-react.md — render, screen queries, userEvent vs fireEvent, role queries

From the file to a first result

The download contains exactly the content displayed on this page. This copy may differ from the latest version in the source repository.

View the source and supporting files

This download contains SKILL.md only. Any scripts, references, templates and dependencies are not included. Get the required files from the source, preserving their directory structure, before continuing.

1. Download the file

Download SKILL.md

From the root of a test project, save the file as .skill-downloads/unit-testing-patterns-mm8o524q/SKILL.md, or use the command below. This folder is for inspecting the skill before installation.

Command for macOS/Linux or WSL: requires a POSIX shell and curl. On Windows without WSL, use the download button and create the folder manually.

mkdir -p '.skill-downloads/unit-testing-patterns-mm8o524q' && curl --fail --show-error --location 'https://skills-guides.com/api/skills/unit-testing-patterns-mm8o524q/download' --output '.skill-downloads/unit-testing-patterns-mm8o524q/SKILL.md.part' && mv '.skill-downloads/unit-testing-patterns-mm8o524q/SKILL.md.part' '.skill-downloads/unit-testing-patterns-mm8o524q/SKILL.md'

2. Check prerequisites

Read SKILL.md before using it. If it references scripts or external services, inspect them and prepare the required access in your test environment.

Tools declared by the author (check availability in your agent): Read, Grep, Glob

No recognized prerequisites section in this file. This does not mean it is self-contained: libraries, tools and access requirements may be mentioned elsewhere in the content or source repository.

The platforms on this page are catalog indications. The paths below follow tool documentation; they do not prove this skill has been run in those tools. No minimum tool version is confirmed for this listing.

3. Load the skill

After inspection, copy the complete folder into your project using one of the commands below, then open a new tool session. The command stops if a folder with the same name already exists: compare the files before replacing it.

Claude Code

test -f '.skill-downloads/unit-testing-patterns-mm8o524q/SKILL.md' && test -s '.skill-downloads/unit-testing-patterns-mm8o524q/SKILL.md' && mkdir -p '.claude/skills' && test ! -e '.claude/skills/unit-testing' && cp -R '.skill-downloads/unit-testing-patterns-mm8o524q' '.claude/skills/unit-testing'

OpenSkills

OpenSkills must already be installed. The local install/read procedure is checked with OpenSkills 1.5.0, which requires Node.js ≥ 20.6.0. Catalog slugs are not resolved automatically.

Official OpenSkills installation

openskills install './.skill-downloads/unit-testing-patterns-mm8o524q'

openskills read 'unit-testing-patterns-mm8o524q'

Reading should display the installed file content and its base directory. It does not run the skill or install its dependencies.

For an agent that reads AGENTS.md, then sync the index. This command changes AGENTS.md: review the diff before using it.

openskills sync

Manual method or another tool: attach SKILL.md to a conversation, or open it in an agent that can read files. Include any required supporting resources. No universal folder is recognized by every tool.

4. Try a first task

Use a short, synthetic input: an API endpoint, a small document or an interface brief. In a new conversation, attach the file or give the agent its path, then adapt this request:

Read .skill-downloads/unit-testing-patterns-mm8o524q/SKILL.md and apply its instructions to this example: [describe a test input]. Identify any missing files, dependencies or access. Produce the result requested by the skill without inventing data or running unreviewed scripts.

Expected result: output matching the skill instructions, or a precise list of missing prerequisites. A read confirmation alone does not validate a first use. If an external resource is unavailable, that path remains untested.