## Spec
describe Users do
  include UserSpecHelper

  before(:each) do
    @user = mock(User, valid_user_hash)
    dispatch_to(Users, :index)
  end

  describe "#create in general" do
    before(:each) do
      User.stub!(:new).and_return(@user)
      @user.stub!(:save).and_return(true)
    end

    it "requires username on signup" do
      lambda do # <= line 28
        controller = create_user(:username => "")
        controller.assigns(:user).errors.on(:username).should_not be_nil # <= line 30
        controller.should be_successful
      end.should_not change(User, :count)
    end
  end
end

## Result
Spec::Mocks::MockExpectationError in 'Users#create in general requires username on signup'
Mock 'User' received unexpected message :errors with (no args)
./spec/controllers/users_spec.rb:30:
./spec/controllers/users_spec.rb:28:

## UserSpecHelper
module UserSpecHelper
  def valid_user_hash
    {:username => "Blinchik", :password => "665665", :password_confirmation => "665665"}
  end

  def create_user(options = {})
    dispatch_to(Users, :create, :user => valid_user_hash.merge(options))
  end
end