add unit tests for shared database synchronisation

spec/support/shared_database.rb

@@ -0,0 +1,29 @@
+# http://stackoverflow.com/questions/8774227
+# http://blog.plataformatec.com.br/2011/12/three-tips-to-improve-the-performance-of-your-test-suite
+class ActiveRecord::Base
+    mattr_accessor :shared_connection
+    @@shared_connection = nil
+       
+    def self.connection
+      @@shared_connection || retrieve_connection
+    end
+end
+# Forces all threads to share the same connection. This works on
+# Capybara because it starts the web server in a thread.
+ActiveRecord::Base.shared_connection = ActiveRecord::Base.connection
+
+ActiveSupport.on_load(:after_initialize) do
+  # We simulate the shared database by pointing to our own database.
+  #   This allows running tests without additional database setup.
+  #   But take care when designing tests using the shared database.
+  SharedSupplier.establish_connection Rails.env
+  SharedArticle.establish_connection Rails.env
+  # hack for different structure of shared database
+  SharedArticle.class_eval do
+    alias_attribute :number, :order_number
+    alias_attribute :updated_on, :updated_at
+    def self.find_by_number(n)
+      find_by_order_number(n)
+    end
+  end
+end