#2768 Tests should see all cookies, not just those that are created or changed in the controller

I've noticed that when testing cookies, the test can only see the
values of cookies that have been changed in actions and doesn't take
into account what the cookie was set to originally.

For example, this test passes (given do_something doesn't nothing to
the cookie) when you'd expect cookie['foo'] to equal 'bar'.

def test_should_delete_the_cookie
  @request.cookies['foo'] = 'bar'
  get :do_something
  assert_nil cookies['foo']
end

I've created a ticket:
https://rails.lighthouseapp.com/projects/8994/tickets/2768-tests-should-see-all-cookies-not-just-those-that-are-created-or-changed-in-the-controller#ticket-2768-1

which includes a patch.