great feature spec example

```rb
feature 'User views all books' do
  scenario 'list all books' do
    create(:book, title: 'Practical Vim')
    create(:book, title: 'The Giver')

    visit books_path

    expect(page).to have_book('Practical Vim')
    expect(page).to have_book('The Giver')
  end

  # ...

  def have_book(title)
    have_selector('.book', text: title)
  end
end

```