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TypeScript Academy · Lesson

Jest Setup for TypeScript with ts-jest

Install and configure ts-jest for a TypeScript project.

Jest Setup for TypeScript with ts-jest is a free TypeScript Academy lesson on CoddyKit — 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, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

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.

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, and the TypeScript Academy course includes 4 lessons in total. 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.

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; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.

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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