JEST

🚀 Modern TypeScript + Jest playground with ESLint (Flat Config), Prettier, Husky, and comprehensive CI/CD pipeline.

📋 Stack Overview

Core Technologies

• TypeScript 5.9.3 - Strict type checking with modern ES2022 features
• Jest 30.2.0 - Testing framework with comprehensive coverage reporting
• Yarn 4.5.3 - Modern package manager with Plug'n'Play support

Development Tools

• ESLint 9.39.2 - Code quality with TypeScript support and flat config
• Prettier 3.7.4 - Code formatting with consistent style
• Husky 9.1.7 - Git hooks for pre-commit quality checks
• lint-staged 16.2.7 - Run linters on staged files

CI/CD & Automation

• GitHub Actions - Automated testing on Node.js 20.x & 22.x
• Dependency Updates - Weekly automated dependency management
• Coverage Reporting - Integrated with Codecov
• Build Pipeline - Type checking and artifact generation

🚀 Requirements

• Node.js 20+ - Latest LTS version recommended
• Yarn 4.5.3 - Enabled via Corepack: corepack enable

⚡ Quick Start

# Install dependencies
yarn install

# Run all tests
yarn test

# Watch tests interactively
yarn test:debug

# Type checking
yarn type-check

# Lint and format
yarn lint:fix && yarn format

📜 Available Scripts

Testing

• test — Run all Jest tests
• test:debug — Run Jest in interactive watch mode
• test:watch — Shorthand for watch mode
• test:coverage — Run tests with coverage report
• test:ci — CI-optimized test run with coverage
• test:changed — Run tests only for changed files
• test:related — Run tests related to changed files

Code Quality

• lint — Run ESLint with cache and zero warnings tolerance
• lint:fix — Run ESLint with auto-fix and cache
• lint:report — Generate JSON lint report
• format — Format code with Prettier
• format:check — Check code formatting without changes
• type-check — Run TypeScript type checking
• type-check:watch — Watch mode for type checking

Maintenance

• update:deps — Interactive dependency upgrades
• update:patches - Apply package patches
• clean — Remove build artifacts and cache
• clean:deps — Clean reinstall of dependencies
• prepare — Setup Git hooks
• pre-commit — Run lint-staged manually
• postinstall — Setup development environment

Linting & formatting

The repo uses ESLint (Flat Config) for code quality and Prettier for formatting. Conflicting style rules are disabled via eslint-config-prettier.

• Detailed docs: see docs/linting.md
• VS Code workspace is preconfigured in .vscode/ to format and fix on save
• Pre-commit hooks (husky + lint-staged) auto-run Prettier and ESLint on staged files

Running Jest directly

Run all tests:

yarn jest

Run all tests with watch:

jest -i --watchAll
# or
yarn test:debug

Run a specific test file:

yarn jest getFixedNumber

Recommended Extension for VS Code

'orta.vscode-jest'

Recommended VS Code setting for see inline hints

  "javascript.inlayHints.functionLikeReturnTypes.enabled": true,
  "javascript.inlayHints.parameterTypes.enabled": true,
  "javascript.inlayHints.propertyDeclarationTypes.enabled": true,
  "javascript.inlayHints.variableTypes.enabled": true,

Further reading

• Official Jest docs: English · Russian
• Linting & formatting: docs/linting.md

Docs

• Linting & formatting setup: docs/linting.md