Jest is considered a test runner in JavaScript and you are able to access DOM via the jsdom. While the jsdom is an approximation that this browser works but it is such a great enough for the component of testing react. Jest also provides a good iteration speed that is combined with effective features, for example mocking the modules and timers.  So you are able to have further control over how a code executes it. 

The library of React Testing is a package of helpers that let you check the React components without responding to their details of an activity implementation. This method creates a refactoring breeze as well as nudges you towards the best practices on accessibility.

Below is one of the useful functions with Jest as well as the problem that users dealt with the “command not found: jest” error. Let’s follow our post to get it!

When does it happen?

you get a test data as follow:

import React from 'react';
import ReactDOM from 'react-dom';
import App from './components/Calculator';
import { getAction, getResult } from './actions/'
import {shallow} from 'enzyme';
import toJson from 'enzyme-to-json';
import Enzyme from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';
Enzyme.configure({ adapter: new Adapter() });
it('renders without crashing', () => {
  const wrapper = shallow(<App />)
  expect(toJson(wrapper)).toMatchSnapshot();
});
it('displays the choosen operator', () => {
  const action = {
      type: 'GET_ACTION',
      operator: '+'
    };
  expect(getAction("+")).toEqual(action)
})
it('displays the typed digit', () => {
  const action = {
    type: 'GET_RESULT',
    n: 3
  };
  expect(getResult(3)).toEqual(action);
})
it('checks that the clickevent for getNumber is called',() => {
  const clickEvent = jest.fn();
  const p = shallow(<p data-n="1" onClick={clickEvent}>1</p>)
  p.simulate('click')
  expect(clickEvent).toBeCalled();
})

Moreover, the code of a packaje.json is here:

{
  "name": "my-app",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "react": "^16.2.0",
    "react-dom": "^16.2.0",
    "react-scripts": "1.1.1"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    // "test": "react-scripts test --env=jsdom",
    "test": "jest",
    "eject": "react-scripts eject"
  },
  "devDependencies": {
    "enzyme": "^3.3.0",
    "enzyme-adapter-react-16": "^1.1.1",
    "enzyme-to-json": "^3.3.3",
    "jest": "^22.4.3"
  }
}

But running “jest –updateSnapshot”, you got the following warning:

command not found: jest

Although you checked carefully, the jest is still installed in this system. Let’s see the jest:

Solution for the “command not found: jest” error

If you check the Jest is set up and it still returns the error, it is able to in the ./node_modules/.bin list. So, you are able to add that to the code ./node_modules/.bin/jest –updateSnapshot. When 

When you have jest like a scripts code in the package.json, just run it by npm test — –updateSnapshot. Then npm automatically inserts ./node_modules/.bin toward the path.

Conclusion

We hope you found our post about fixing the  “command not found: jest” error useful. We know that dealing with this problem can be annoying and you don’t want to see it again; therefore, we hope that our information has supported you in resolving it. 

Please leave a comment in the below session if you have any further questions or concerns for us. Thank you so much for taking the time to read and we are always delighted anytime one of our pieces is able to share significant information on this topic!