Test#injectTestHelpers()

This injects the test helpers into the helperContainer object. If an object is provided it will be used as the helperContainer. If helperContainer is not set it will default to window. If a function of the same name has already been defined it will be cached (so that it can be reset if the helper is removed with unregisterHelper or removeTestHelpers).

Any callbacks registered with onInjectHelpers will be called once the helpers have been injected.

Example: App.injectTestHelpers();