Jest Error: 'jest' is not recognized as an internal or external command, operable program or batch file

Try installing jest as a dev dependency.
npm install --save-dev jest

Then run it with npm test. Don't use jest command directly. It's not recommended.
If you want to use jest command use node_modules/.bin/jest.

I fixed this problem only after installing jest globally:

npm install -g jest

You can use "node_modules\.bin\jest" --init if you are on Windows.