How to use TypeScript with Jest
2022/12/61 min read
bookmark this
Introduction
This blog shows how to get start use TypeScript to write code and also write in Jest.
Install Packages
If you have not use Jest, can reference this to get start with Jest with JavaScript, Get Start with Jest.
At here, we'll start install necessary NPM packages for use TypeScript at Jest and the code.
npm install --save-dev @babel/core @babel/preset-env @babel/preset-typescript @jest/globals @types/jest babel-jest ts-jest ts-node typescript
Create babel.config.js
module.exports = {
presets: [
['@babel/preset-env', {targets: {node: 'current'}}],
'@babel/preset-typescript',
],
};
Create jest.config.ts
export default {
clearMocks: true,
collectCoverage: true,
coverageDirectory: "coverage"
}
Change the Code sample.js
to TypeScript sample.ts
Change the Jest sample.test.js
to TypeScript sample.test.ts
import {exponent, subtraction, sum} from '../src/sample';
import {describe, expect, test} from '@jest/globals';
describe('calculator', () => {
test('test sum', () => {
expect(sum(1, 2)).toBe(3);
});
test('test subtraction', () => {
expect(subtraction(10, 2)).toBe(8);
});
test('test exponent', () => {
expect(exponent(5, 2)).toBe(25);
});
})
Run npm run test
Now, if run npm run test
and if everything works, should see test all passed and 100% coverage.