def should_see_button(button_text, scope={})
      in_scope(scope) do
        xpath = XPath::HTML.button(button_text)
        if !page.has_xpath?(xpath)
          raise Kelp::Unexpected, "Expected to see button '#{button_text}', but button does not exist."
        end
      end
    end
def should_see_button(button_text, scope={})
      in_scope(scope) do
        xpath = XPath::HTML.button(button_text)
        if !page.has_xpath?(xpath)
          raise Kelp::Unexpected, "Expected to see button '#{button_text}', but button does not exist."
        end
      end
    end
Verify that a button with the given text appears on the page.
 Works for `<input...>` as well as `<button...>` elements.

 @example
   should_see_button "Submit"
   should_see_button "Save changes", :within => "#preferences"

 @param [String] button_text
   Visible button text to look for
 @param [Hash] scope
   Scoping keywords as understood by {#in_scope}

 @raise [Kelp::Unexpected]
   If no button with the given text exists in the given scope

 @since 0.1.9