In general, try to [avoid instance variables](http://betterspecs.org/#let) in rspec tests. Suggesting something like

```Ruby
let(:ideas) { FactoryGirl.create_list :idea, 10 }
let(:idea) { idea.first }
let(:attrs) { { title:'Updated title', description:'Updated description' } }

before { put :update, id: idea.id, idea: attrs }

it "updates the idea" do
  expect(idea.reload.title).to eq attrs[:title]
end
```

Also, for future thought, try to prefer `expect` over `should` (http://betterspecs.org/#expect). Frankly I like the way you did it better, but that's the way rspec is moving.