Step 1: Created react app using typescript template and npm

npx create-react-app react-typescript-app --template typescript --use-npm

Step 2: downgraded react, react-dom version and clean up

• removed package-lock.json file and updated the package.json file with react@16, react-dom@16

Step 3: added todos module

Step 4: Integrated the jest, enzyme into app and updated app.test

refs. https://github.com/cedrickchee/react-typescript-jest-enzyme-testing