unit testing using jest code example

Example 1: what is jest

Jest is a JavaScript testing framework maintained by Facebook, Inc. with a
focus on simplicity.

It works with projects using: Babel, TypeScript, Node.js, React, Angular and
Vue.js.

It aims to work out of the box and config free.

Example 2: testing with jest

npm i jest --save -dev
-> In Package.json change the Script object(watchAll - jest will run auto)
"test" : "jest --watchAll"
-> test file should be named such way that re used by jest can recognize it
like filename.<test> or <spec> or skip it.js
Ex: sum.test.js or sum.spec.js or sum.js
-> require the target for testing file in this test file then enjoy testing.
-> visit jestWebsite-> Docs.