So, this was quite an interesting problem I have been running into.

I am currently building a backbone.js - Rails app. Generally just building this for learning purposes. I am (like any good rails dev) doing my best at TDD/BDD and I ran into a problem with capybara.

I have an integration spec that merely tests root_path works (Backbone history starts, displays initial information, etc...).

require 'spec_helper'



describe RentalProperties, js: true do

  describe GET / do

    it should show a list of properties do

      visit root_path

      eventually{page.should have_content(Something)}

    end

  end

end

I am running tests with jasmine, sinon, and capybara/rspec/webkit. I am loosely following both the Rspec on Rails book by thoughtbot (awesome book by the way), and this tutorial: http://tinnedfruit.com/2011/03/03/testing-backbone-apps-with-jasmine-sinon.html.

When running the above spec, I came across this error:

undefined|0|ReferenceError: Strict mode forbids implicit creation of global property 'csrf_token'

I took a long time sorting this out because there's really nothing google-able for this error.

Eventually I stumbled across using use strict-mode in JS. Essentially this will use some new EMCA5 script conventions. It will catch more coding bloopers, and keep you from accessing global variables. All good things.

So I check, and in my sinon.js file, I see:

use strict;

on line 36 of the file. Lo and behold I comment out the line, and my tests work just fine.

Here is my question: Why did use strict mess up csrf? I am assuming this has something to do with csrf_meta_tags in my rails layout. If possible I would like to put this line back in sinon js as I assume its the right thing to do

Does anyone have more information on this? I appreciate any details in advance!!