error_step.rb

Then /^the following fields should be required:$/ do |fields|
  fields.rows_hash.each do |field, custom_message|
    node = find('input[type="submit"]', :message => "Unable to locate the submit button to click on")
    node.click
    Then %{the "#{field}" field should have the error "#{custom_message.presence || "can't be blank"}"}
  end
end

form.feature

  Scenario: Required fields for the signup form
    Given I am on the home page
     When I follow "Sign up for an account"
     Then the following fields should be required:
       | Name     | can't be blank |
       | Email    | can't be blank |
       | Password ||