How To Run Jest Unit Tests In a Typescript Project
Follow these steps to set up Jest unit tests in a TypeScript project.
IMPORTANT
This guide uses the ts-jest npm library to simplify the setup. As described on the npm page, ts-jest is a Jest transformer with source map support that allows you to use Jest to test projects written in TypeScript.
Step 1 - Create your project folder and initialize npm
Run the following commands to create a new project folder and initialize npm. Replace my-project
with the name of your project.
mkdir my-project
cd my-project
npm init -y
Step 2 - Install prerequsites
Run the following command to install the necessary npm packages.
npm install --save-dev typescript jest ts-jest @types/jest
Step 3 - Setup the typescript project
Run the following command to create a tsconfig.json
file in your project folder.
npx tsc --init
Step 4 - Configure Jest
Run the following command to create a Jest configuration file that is compatible with Typescript.
npx ts-jest config:init
This command will create the jest.config.js
file in your project folder.
Step 5 - Create some code and unit tests
Create the src/calculator.ts
file as below:
export function add(a: number, b: number): number {
return a + b;
}
Create the tests for the calculator in the test/calculator.spec.ts
file as below:
import { add } from "../src/calculator";
describe("Calculator tests", () => {
it("should add two numbers", () => {
expect(add(1, 2)).toBe(3);
});
})
Step 6 - Run the tests
Run the tests from the command line as below:
npx jest
You should see these results in the console:
❯ npx jest
PASS test/calculator.spec.ts
Calculator tests
✓ should add two numbers (1 ms)
Test Suites: 1 passed, 1 total
Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 1.385 s, estimated 2 s
Ran all test suites.
Step 7 - Add test script in package.json file
To run the tests via the npm test
command you can change the scripts section in the package.json
file to look like this:
"scripts": {
"test": "jest"
}
Now you should be able to run the tests with the npm test
command and get the same output in the console.
Top comments (0)