Ember global App variable

I am developing my Ember as an addon & inside my tests\dummy\app.js, I have

App = Ember.Application.extend({
  modulePrefix: config.modulePrefix,
});

My question is related to accessing global variable acrosss the Ember app.

Do I have to do

window.App = App;

in the above place only (i.e. where I'll have Ember.Application.extend())

OR can I do in some other place as well ?