TypeScript Academy · Lesson

Jest Setup for TypeScript with ts-jest

Install and configure ts-jest for a TypeScript project.

Lesson 1 of 413 steps

Jest Setup for TypeScript with ts-jest is a free TypeScript Academy lesson on CoddyKit. This is lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the TypeScript Academy learning path, and your progress syncs across the web and the CoddyKit app. The TypeScript Academy course includes 4 lessons in total.

Welcome

Configure Jest to run TypeScript tests directly using ts-jest or Babel with TypeScript support.

Installing ts-jest

Install Jest, ts-jest, and TypeScript types.
npm install --save-dev jest ts-jest @types/jest typescript

jest.config.ts

Configure Jest to use ts-jest as the transform.
export default {
  preset: 'ts-jest',
  testEnvironment: 'node',
  globals: { 'ts-jest': { tsconfig: 'tsconfig.json' } },
};

tsconfig for Tests

You may have a separate tsconfig.test.json for test-specific settings.
{ "extends": "./tsconfig.json", "compilerOptions": { "types": ["jest"] } }

Running Tests

Run tests with the jest command.
npx jest
npx jest --watch
npx jest --coverage

Vitest Alternative

Vitest is faster than Jest for TypeScript projects and requires minimal config.
npm install --save-dev vitest
// vitest.config.ts: { test: { environment: 'node' } }

SWC Transform for Speed

Use @swc/jest instead of ts-jest for significantly faster test execution.
npm install --save-dev @swc/core @swc/jest
// jest.config.ts: transform: { "^.+\.[tj]s$": ["@swc/jest"] }

Path Aliases in Tests

Configure moduleNameMapper to resolve path aliases in Jest.
{ moduleNameMapper: { '^@/(.*)$': '<rootDir>/src/$1' } }

Test File Naming

TypeScript test files use .test.ts or .spec.ts extensions.

Type Checking in Tests

ts-jest runs type checking during tests unless isolated: false is set.
// ts-jest: { diagnostics: false } — disable type checking for speed

ESM Support

For ESM TypeScript with Jest, set NODE_OPTIONS=--experimental-vm-modules.
NODE_OPTIONS=--experimental-vm-modules npx jest

Quick Check

Which ts-jest setting skips TypeScript type checking during test runs for speed?

Recap

Jest Setup for TypeScript with ts-jest: mastered the key concepts and patterns.
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Frequently Asked Questions

Is the “Jest Setup for TypeScript with ts-jest” lesson free?

Yes — the full text of “Jest Setup for TypeScript with ts-jest” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the TypeScript Academy course, upgrade to CoddyKit PRO. The TypeScript Academy course includes 4 lessons in total.

What will I learn in “Jest Setup for TypeScript with ts-jest”?

Install and configure ts-jest for a TypeScript project. You practise TypeScript Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start TypeScript Academy?

No prior experience is required. TypeScript Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 1 of 4.

How long does the “Jest Setup for TypeScript with ts-jest” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this TypeScript Academy lesson?

Yes. Every TypeScript Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Jest Setup for TypeScript with ts-jest
  2. Writing Type-Safe Unit Tests
  3. Mocking Modules and Functions in TypeScript
  4. Type Testing with expectTypeOf and tsd
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