_form.html.haml

= form_for @card do |f|
  -if @card.errors.any?
    #error_explanation
      %h2= "#{pluralize(@card.errors.count, "error")} prohibited this card from being saved:"
      %ul
        - @card.errors.full_messages.each do |msg|
          %li= msg

  .field
    = f.label :card_name
    = f.text_field :card_name
  .field
    = f.label :card_type
    = f.text_field :card_type
  .actions
    = f.submit 'Save New Card'

card_steps.rb

def add_card valid_card
  visit '/cards/new'
  fill_in "card_name", :with => card[:card_name]
  fill_in "card_type", :with => card[:card_type]
  click_button "Save New Card"
end

error

Feature: enter cards
  In order to to have cards in the database
  A user
  Should be able to add cards to the database

  Background:            # features/cards/enter_cards.feature:6
    Given I am logged in # features/step_definitions/user_steps.rb:28

  Scenario: User enters a valid card                  # features/cards/enter_cards.feature:9
    When I enter valid card data                      # features/step_definitions/card_steps.rb:27
      cannot fill in, no text field, text area or password field with id, name, or label 'card_name' found (Capybara::ElementNotFound)
      (eval):2:in `fill_in'
      ./features/step_definitions/card_steps.rb:19:in `add_card'
      ./features/step_definitions/card_steps.rb:28:in `/^I enter valid card data$/'
      features/cards/enter_cards.feature:10:in `When I enter valid card data'
    Then I should see a successful card added message # features/step_definitions/card_steps.rb:42

new.html.haml

%h1 New card

= render 'form'

= link_to 'Back', cards_path