Don't mutate the parent configuration

lib/i18n_alchemy.rb

@@ -28,10 +28,10 @@ module ClassMethods
       def localize(*methods)
         options = methods.extract_options!
         parser  = options[:using]
-        methods = methods.each_with_object(localized_methods) do |method_name, hash|
+        methods = methods.each_with_object({}) do |method_name, hash|
           hash[method_name] = parser
         end
-        self.localized_methods = methods
+        self.localized_methods = self.localized_methods.merge(methods)
       end
     end
   end

test/db/test_schema.rb

@@ -20,6 +20,7 @@
 
   create_table :suppliers do |t|
     t.string     :name
+    t.timestamp  :created_at
   end
 
   create_table :accounts do |t|

test/models/supplier.rb

@@ -7,3 +7,7 @@ class Supplier < ActiveRecord::Base
   accepts_nested_attributes_for :products
   accepts_nested_attributes_for :account
 end
+
+class AnotherSupplier < Supplier
+  localize :created_at, :using => :timestamp
+end

test/models_test.rb

@@ -0,0 +1,7 @@
+require "test_helper"
+
+class ModelsTest < I18n::Alchemy::TestCase
+  def test_inheritance_configuration
+    assert Supplier.localized_methods != AnotherSupplier.localized_methods
+  end
+end