How to spec a scoped new object in the controller

How should I spec this nested build:

#projects_controller.rb
def new
  @account.projects.build
end

So far I have something like this:

#projects_controller_spec.rb
describe ProectssController do
  describe "GET new" do
    let(:account) { mock_model(Account) }
    let(:project) { mock_model(Project).as_null_object }

    before do
      Account.stub(:find_by_subdomain!).and_retur开发者_JAVA百科n(account)
      #Project.should_receive(:build).with(:account_id => account.id).and_return(project)
    end

    it "assigns @project" do
      get :new
      assigns[:project].should eq(project)
    end
  end
end

Not sure how I should be specing this...

The assignment is missing in ProjectsController#new. Should be:

def new
  # ...
  @project = @account.projects.build
  # ...
end

Then you can stub returning a double as you intended:

it "assigns @project" do
  account = mock_model(Account) 
  Account.stub(:find_by_subdomain!).and_return(account)
  project = account.stub_chain(:projects,:build) { mock_model(Project) }
  get :new
  assigns(:project).should == project
end

In general, I recommend stubbing and mocking as little as possible. I recommend using something like Factory Girl to create real database objects for the tests to interact with. That means that Account and Project would be real ActiveRecord classes, and then @account would be a real AR object with a projects association that works just like it does in production. This is important, since otherwise you're just testing to the implementation you've written, and haven't actually tested that your code functions when it's actually using ActiveRecord.

Once you can do that, I would recommend simply checking things you care about for the Project model, e.g.:

assigns[:project].should be_instance_of(Project)
assigns[:project].should be_new_record
assigns[:project].account.should == logged_in_user

Hope this helps!