Uint-Testing of Express apis and React components.

Unit testing for [Express](https://expressjs.com/) apis using [Chai](https://www.chaijs.com/) and [Mocha](https://mochajs.org/) . And writing tests for [React](https://reactjs.org/) components using [Jest](https://jestjs.io/) and [RTL](https://testing-library.com/docs/react-testing-library/setup).