this has not covered everything, IMHO you should check:

* assigns is correctly assigned
* response code
* rendered template

For example

```
describe 'GET index' do
  before do
    get :index
  end

  specify do
    expect(response.response_code).to eq 200
    expect(assigns(:companies)).to eq [company]
    expect(response).to render_template('companies/index')
  end
end
```