Mocha: How to mock session storage when running a test?

[purezen]

I am trying to setup mocha for my reactjs app.
However, running the command mocha --compilers js:babel-register --recursive produces an error saying

mocha --compilers js:babel-register --recursive

/Users/purezen_/workspace/webapp/src/js/data/reducers/auth.js:31
var auth = sessionStorage.getItem('auth');
           ^

ReferenceError: sessionStorage is not defined
    at Object.<anonymous> (auth.js:5:14)
    at Module._compile (module.js:397:26)
    at loader (/Users/purezen_/workspace/kredx-fe/client/node_modules/babel-register/lib/node.js:158:5)

even when I have included code to mock session storage inside the test file according to http://stackoverflow.com/q/11485420/1509855

[purezen]

Was able to get it working using https://github.com/letsrock-today/mock-local-storage.

[roysud]

This was a lifesaver! Thanks a ton @purezen
I used mock-local-storage to mock my sessionStorage. It was as simple as just installing with npm and running the test. No additional code needs to be written!!

[sunilsp77]

How to do this?
It is not working for me.
Please help

[sunilsp77]

Do I need to change any file?