How do I declare a variable in a specific scope in coffeescript?

You are doing it the right way.

This is described in the CoffeeScript documentation. I wouldn’t worry about the JS that it creates. Yes, it is a bit messy if you were to write it yourself, but this is one of the things that you have to live with when you use a re-writer like CoffeeScript.

You do, however, have a couple of options which are pretty nice.

You can put the variables in the current context if you wish (which happens to be your jasmine.Spec object for the curious, so it is a relatively safe and appropriate place to be putting variables… just don’t overwrite existing vars in the context.):

describe 'PhoneDetailCtrl', () ->
  beforeEach () ->
    @scope = angular.scope()
    @$browser = @scope.$service('$browser')

it 'should fetch phone detail', () ->
  @scope.params = {phoneId:'xyz'}
  #... etc

You can also setup your own variable in which to store things

describe 'PhoneDetailCtrl', () ->
  setup = {}

  beforeEach () ->
    setup.scope = angular.scope()
    setup.$browser = setup.scope.$service('$browser')

  it 'should fetch phone detail', () ->
    setup.scope.params = {phoneId:'xyz'}
    #... etc