# Cui Javascript Unit Testing

> Jest unit testing standards covering configuration, test structure, testing patterns, and coverage requirements

- Skill: `majiayu000/cui-javascript-unit-testing` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds add majiayu000/cui-javascript-unit-testing`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/cui-javascript-unit-testing/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/cui-javascript-unit-testing

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# JavaScript Unit Testing Standards

## Overview

This skill provides comprehensive Jest unit testing standards for CUI JavaScript projects, covering Jest configuration, test organization, component testing patterns, mocking strategies, and coverage requirements.

## Prerequisites

To effectively use this skill, you should have:

- JavaScript testing experience with Jest framework
- Understanding of unit testing principles (AAA pattern, test isolation)
- Familiarity with DOM testing and component testing concepts
- Knowledge of mocking and test doubles

## Standards Documents

This skill includes the following standards documents:

- **jest-configuration.md** - Jest setup, package.json config, transform patterns, module mapping
- **test-structure.md** - Test file organization, naming conventions, setup files, directory structure
- **testing-patterns.md** - Component testing, mocking strategies, assertions, AAA pattern
- **coverage-standards.md** - Coverage thresholds (80%), reporting formats, collection strategies

## What This Skill Provides

### Jest Configuration
- **Core Setup**: Jest environment configuration (jsdom), testMatch patterns
- **Module Mapping**: Mock configuration for Lit, DevUI, and other dependencies
- **Transform Configuration**: Babel-jest setup for ES modules, transformIgnorePatterns
- **Setup Files**: Global test setup, DOM polyfills, mock implementations

### Test Structure
- **File Organization**: Standard directory structure (components/, mocks/, setup/, utils/)
- **Naming Conventions**: Component tests (*.test.js), integration tests, utility tests
- **Setup Files**: jest.setup.js, jest.setup-dom.js configuration patterns
- **Test File Structure**: Describe blocks, beforeEach/afterEach patterns

### Testing Patterns
- **Component Testing**: Lit component test structure, rendering tests, property tests
- **Mocking Strategies**: Lit framework mocks, DevUI mocks, external dependency mocking
- **Assertion Patterns**: Jest matchers, @testing-library/jest-dom assertions
- **AAA Pattern**: Arrange-Act-Assert structure, test isolation principles

### Coverage Standards
- **Minimum Thresholds**: 80% for branches, functions, lines, statements
- **Coverage Collection**: Strategies for mocked vs actual source files
- **Reporting Formats**: text, lcov, html, cobertura for different use cases
- **Coverage Directory**: target/coverage integration with build system

## When to Activate

This skill should be activated when:

1. **Writing Tests**: Creating new Jest unit tests for JavaScript code
2. **Configuring Jest**: Setting up Jest for a new project or updating configuration
3. **Test Review**: Reviewing test quality and coverage compliance
4. **Mocking**: Implementing mocks for Lit components or external dependencies
5. **Coverage Analysis**: Understanding or improving test coverage
6. **Test Structure**: Organizing test files and setup
7. **CI/CD Integration**: Configuring test execution in build pipelines

## Workflow

When this skill is activated:

### 1. Understand Context
- Identify the specific testing task or requirement
- Determine which standards documents are most relevant
- Check existing project Jest configuration

### 2. Apply Standards
- Reference appropriate standards documents for guidance
- Follow Jest configuration patterns from jest-configuration.md
- Organize test files according to test-structure.md
- Apply testing patterns from testing-patterns.md
- Ensure coverage meets thresholds from coverage-standards.md

### 3. Quality Assurance
- Run tests to verify they execute correctly
- Check coverage reports meet 80% thresholds
- Verify mocks are properly configured
- Ensure tests are isolated and independent
- Validate test naming and organization

### 4. Documentation
- Document complex mocking strategies with clear comments
- Explain non-obvious test setup or configuration
- Note any project-specific test patterns
- Update README if adding new test utilities

## Tool Access

This skill provides access to Jest testing standards through:
- Read tool for accessing standards documents
- Standards documents use Markdown format for compatibility
- All standards are self-contained within this skill
- Cross-references between standards use relative paths

## Integration Notes

### Related Skills
For comprehensive JavaScript development, this skill works with:
- cui-javascript skill - Core JavaScript patterns and code quality
- cui-css skill - CSS testing patterns (if applicable)
- Other testing skills (E2E testing to be provided in separate skill)

### Build Integration
Jest testing integrates with:
- npm for package management and test execution
- Maven frontend-maven-plugin for build automation
- Jest CLI for test execution and coverage reporting
- Babel for ES module transformation

### Quality Tools
Test quality is enforced through:
- Jest framework for test execution
- @testing-library/jest-dom for enhanced DOM assertions
- Coverage reports for quality gates
- ESLint jest plugin for test code quality

## Best Practices

When writing Jest tests in CUI projects:

1. **Meet coverage thresholds** - 80% minimum for all metrics
2. **Use jsdom environment** for DOM and component testing
3. **Mock external dependencies** - Lit, DevUI, and other frameworks
4. **Follow AAA pattern** - Arrange, Act, Assert for clarity
5. **Keep tests isolated** - Independent, no shared state
6. **Organize logically** - Group related tests with describe blocks
7. **Use descriptive names** - Test names explain expected behavior
8. **Setup properly** - Use jest.setup.js and jest.setup-dom.js for global config