TypeError: environment.setup is not a function in React Testing

Question

I was trying to implement the example shown in Jest website: Getting started with Jest.

While running npm test on I was getting the following error:

FAIL  src/sum.test.js   ● Test suite failed to run      TypeError: environment.setup is not a function        at node_modules/jest-runner/build/run_test.js:112:23 

sum.js:

function sum(a, b){   return a+b; } module.exports = sum; 

sum.test.js:

const sum = require('./sum');  test('adding sum function', () => {   expect(sum(234,4)).toBe(238); }) 

sum.js and sum.test.js are an exact copy of the example shown in Getting started with Jest.

package.json:

{   "name": "jest-demo-test",   "version": "0.1.0",   "private": true,   "dependencies": {     "react": "^16.2.0",     "react-dom": "^16.2.0",     "react-scripts": "1.0.17"   },   "scripts": {     "start": "react-scripts start",     "build": "react-scripts build",     "test": "jest",     "eject": "react-scripts eject"   },   "devDependencies": {     "jest": "^22.0.4"   } } 

So, how can I get rid of TypeError: environment.setup is not a function error?

Answer 1

Jest is included with react-scripts. The error is due to a conflict that arose when you installed Jest in a project started with react-scripts. The "Getting started with Jest" guide expects a 'clean' project.

Simply remove Jest from your (dev)dependencies and it should work.

If you want to use Jest for testing React components (which you probably do), you need to modify your test script in package.json to react-scripts test --env=jsdom, as it was.