testing-patterns

name	testing-patterns
description	Testing patterns for Jest unit and integration tests. Use when writing tests, setting up test fixtures, or validating implementations. Jest only -- no no E2E framework. Tests live in `tests/` directory.

Testing Patterns Skill

TEMPLATE: This skill uses {{PLACEHOLDER}} tokens. Replace with your project values before use.

Purpose

Guide consistent and effective testing. Routes to existing test patterns and provides evidence templates.

When This Skill Applies

• Writing unit or integration tests
• Setting up test fixtures
• Running test suites
• Packaging test evidence

Critical Rules

FORBIDDEN

// Shared test state causes flaky tests
let sharedData: any;
beforeAll(() => { sharedData = createData(); });

// Hard-coded IDs cause test pollution
const userId = "user-123";

CORRECT

// Isolated test state per test
beforeEach(() => {
  const testData = createTestData();
});

// Unique identifiers
const userId = `user-${crypto.randomUUID()}`;

Test Commands

npm test                              # Run all tests
npx jest tests/specific-file.test.ts  # Run a single test file
npx jest --testPathPattern="keyword"  # Run tests matching pattern
npm test -- --coverage                # Run with coverage

Coverage Thresholds

Metric	Threshold
Branches	70%
Functions	80%
Lines	80%
Statements	80%

Test Directory Structure

tests/
├── unit/              # Fast, isolated tests
├── integration/       # API and database tests
└── setup.ts           # Global test setup (if any)

Evidence Template

**Test Execution Evidence**

**Test Suite**: [unit/integration]
**Files Changed**: [list files]

**Test Results:**
- Total Tests: [X]
- Passed: [X]
- Failed: [0]

**Coverage** (if applicable):
- Branches: X% (threshold: 70%)
- Functions: X% (threshold: 80%)
- Lines: X% (threshold: 80%)
- Statements: X% (threshold: 80%)

**Commands Run:**
```bash
npm test -- --coverage

## Reference

- **Jest Config**: `jest.config.js`
- **Test Directory**: `tests/`
- **Pattern Library**: `patterns_library/testing/`