react-ga

see errors “ReactGA.initialize must be called first or GoogleAnalytics should be loaded manually”

 PASS  src/index.test.js
  ● Console

    console.warn node_modules/react-ga/dist/react-ga.js:110
      [react-ga] ReactGA.initialize must be called first or GoogleAnalytics should be loaded manually
    console.warn node_modules/react-ga/dist/react-ga.js:110
      [react-ga] ReactGA.initialize must be called first or GoogleAnalytics should be loaded manually
    console.warn node_modules/react-ga/dist/react-ga.js:110
      [react-ga] ReactGA.initialize must be called first or GoogleAnalytics should be loaded manually

 PASS  src/pages.test.js

modify index.test.js file, add a react-ga mock

jest.mock('react-ga')

event method

ReactGA.event({
  category: 'React Component',
  label: 'UserTable',
  action: 'componentDidMount'
})