Testing with datamapper

task_list_test.rb

describe TaskList do
  let(:list) { TaskList.new }
  let(:todo) { mock('todo').as_null_object }
  
  describe '#tasks' do
    context 'without tasks' do
      it 'returns an empty array' do
        list.tasks.should be_empty
      end
    end
    
    context 'with tasks' do
      before(:each) { list.stub(:tasks).and_return [todo, todo, todo] }
      
      it 'returns an array containing all tasks' do
        list.tasks.should =~ [todo, todo, todo]
      end
    end
  end