Tengo un archivo de prueba así: (estoy usando create-react-app)

 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(); })

y un paquete.json:

 { "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" } }

cuando ejecuto "jest --updateSnapshot" obtengo:

 command not found: jest

pero la broma está instalada.