Skill

unit-testing

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.

Install

npx claudepluginhub rnavarych/alpha-engineer --plugin billy-milligan

Tool Access

This skill is limited to using the following tools:

ReadGrepGlob

Preview

- Setting up Vitest or Jest for a new project

Supporting Assets

references/backend-testing.mdreferences/jest-vitest-patterns.mdreferences/mocking-strategies.mdreferences/react-testing.md

SKILL.md

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Stats

Parent Repo Stars9

Parent Repo Forks0

Last CommitFeb 23, 2026

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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

Unit Testing Patterns

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