Setting up TypeScript in Jest without the need for webpack

Currently, I'm developing an NPM module using TypeScript without the use of Webpack for compiling scripts.

I need some guidance on configuring Jest to properly run tests with TypeScript files. Any recommendations?

// test.spec.ts
import {calc} from './index'

test('shoud...', () => {
  expect(calc()).toBeDefined()
})

// index.ts
import {calc} from './index'

const calc = (a, b) => {
  return a + b
}

Encountered this error message:

testMatch: /__tests__//*.js?(x),**/?(*.)+(spec|test).js?(x) - 0 matches testPathIgnorePatterns: /node_modules/ - 9 matches

typescript jestjs

Answer №1

Step 1: Installation Process

npm i jest @types/jest ts-jest -D

Detailed Explanation:

Begin by installing the Jest framework (jest)
Proceed to install the types for Jest (@types/jest)
Next, install the TypeScript preprocessor for Jest (ts-jest) which enables Jest to transpile TypeScript seamlessly and comes equipped with source-map support.
Ensure that all these packages are saved as your development dependencies (as testing usually falls under npm dev-dependencies)

Step 2: Configuration of Jest Settings

Incorporate the following jest.config.js file into the root directory of your project:

module.exports = {
  "roots": [
    "<rootDir>/src"
  ],
  "transform": {
    "^.+\\.tsx?$": "ts-jest"
  },
}

Meticulous Explanation:

We strongly recommend organizing all TypeScript files within a src folder in your project structure.
Assuming this organizational practice is followed, specify it using the roots option. Additionally, the transform configuration directs Jest to utilize ts-jest for handling ts / tsx files. For more information, refer to the Jest documentation at: https://jestjs.io/docs/en/configuration#transform-object-string-string

Reference Source: https://basarat.gitbooks.io/typescript/docs/testing/jest.html

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