Use the :as option to create the form css class the same way Rails does

It sounds confusing, I know, but Rails uses the :as option as prefix
with the current action, when the option is given, otherwise it uses
dom_class, which behaves differently. For instance, given a @user object:

    With :as => 'user'          => 'user_new' or 'user_edit'
    Without :as, uses dom_class => 'new_user' or 'edit_user'

Weird huh? =)

lib/simple_form/action_view_extensions/form_helper.rb

@@ -64,7 +64,7 @@ module SimpleForm
         else
           record = record.last if record.is_a?(Array)
           action = record.respond_to?(:persisted?) && record.persisted? ? :edit : :new
-          as ? "#{action}_#{as}" : dom_class(record, action)
+          as ? "#{as}_#{action}" : dom_class(record, action)
         end
       end
     end

test/action_view_extensions/form_helper_test.rb

@@ -37,7 +37,7 @@ class FormHelperTest < ActionView::TestCase
     end
   end
 
-  test 'simple form should add object name as css class to form when object is not present' do
+  test 'simple form should add object name as css class to form when object is not present and the :as option is not given' do
     concat(simple_form_for(:user) do |f| end)
     assert_select 'form.simple_form.user'
   end
@@ -45,6 +45,7 @@ class FormHelperTest < ActionView::TestCase
   test 'simple form should add :as option as css class to form when object is not present' do
     concat(simple_form_for(:user, :as => 'superuser') do |f| end)
     assert_select 'form.simple_form.superuser'
+    assert_no_select 'form.simple_form.user'
   end
 
   test 'simple form should add object class name with new prefix as css class to form if record is not persisted' do
@@ -56,7 +57,7 @@ class FormHelperTest < ActionView::TestCase
   test 'simple form should add :as option with new prefix as css class to form if record is not persisted' do
     @user.new_record!
     concat(simple_form_for(@user, :as => 'superuser') do |f| end)
-    assert_select 'form.simple_form.new_superuser'
+    assert_select 'form.simple_form.superuser_new'
   end
 
   test 'simple form should add edit class prefix as css class to form if record is persisted' do
@@ -66,16 +67,16 @@ class FormHelperTest < ActionView::TestCase
 
   test 'simple form should add :as options with edit prefix as css class to form if record is persisted' do
     concat(simple_form_for(@user, :as => 'superuser') do |f| end)
-    assert_select 'form.simple_form.edit_superuser'
+    assert_select 'form.simple_form.superuser_edit'
   end
 
   test 'simple form should not add object class to form if css_class is specified' do
-    concat(simple_form_for(:user, :html => {:class => nil}) do |f| end)
+    concat(simple_form_for(:user, :html => { :class => nil }) do |f| end)
     assert_no_select 'form.user'
   end
 
   test 'simple form should add custom class to form if css_class is specified' do
-    concat(simple_form_for(:user, :html => {:class => 'my_class'}) do |f| end)
+    concat(simple_form_for(:user, :html => { :class => 'my_class' }) do |f| end)
     assert_select 'form.my_class'
   end