deleting the user sets the auhorship of associated cost object to the deleted user

app/models/cost_object.rb

@@ -27,6 +27,9 @@ class CostObject < ActiveRecord::Base
   validates_length_of :subject, :maximum => 255
   validates_length_of :subject, :minimum => 1
 
+  User.before_destroy do |user|
+    replace_author_with_deleted_user user
+  end
 
   def before_validation
     self.author_id = User.current.id if self.new_record?
@@ -150,4 +153,11 @@ class CostObject < ActiveRecord::Base
     return "issue cost_object"
   end
 
+  private
+
+  def self.replace_author_with_deleted_user(user)
+    substitute = DeletedUser.first
+
+    self.update_all ['author_id = ?', substitute.id], ['author_id = ?', user.id]
+  end
 end

spec/models/user_deletion_spec.rb

@@ -0,0 +1,107 @@
+require File.dirname(__FILE__) + '/../spec_helper'
+
+describe User, "#destroy" do
+  let(:user) { Factory.create(:user) }
+  let(:user2) { Factory.create(:user) }
+  let(:substitute_user) { DeletedUser.first }
+
+  before do
+    user
+    user2
+  end
+
+  shared_examples_for "updated journalized associated object" do
+    before do
+      User.current = user2
+      associations.each do |association|
+        associated_instance.send(association.to_s + "=", user2)
+      end
+      associated_instance.save!
+
+      User.current = user # in order to have the content journal created by the user
+      associated_instance.reload
+      associations.each do |association|
+        associated_instance.send(association.to_s + "=", user)
+      end
+      associated_instance.save!
+
+      user.destroy
+      associated_instance.reload
+    end
+
+    it { associated_class.find_by_id(associated_instance.id).should == associated_instance }
+    it "should replace the user on all associations" do
+      associations.each do |association|
+        associated_instance.send(association).should == substitute_user
+      end
+    end
+    it { associated_instance.journals.first.user.should == user2 }
+    it "should update first journal changes" do
+      associations.each do |association|
+        associated_instance.journals.first.changes[association.to_s + "_id"].last.should == user2.id
+      end
+    end
+    it { associated_instance.journals.last.user.should == substitute_user }
+    it "should update second journal changes" do
+      associations.each do |association|
+        associated_instance.journals.last.changes[association.to_s + "_id"].last.should == substitute_user.id
+      end
+    end
+  end
+
+  shared_examples_for "created journalized associated object" do
+    before do
+      User.current = user # in order to have the content journal created by the user
+      associations.each do |association|
+        associated_instance.send(association.to_s + "=", user)
+      end
+      associated_instance.save!
+
+      User.current = user2
+      associated_instance.reload
+      associations.each do |association|
+        associated_instance.send(association.to_s + "=", user2)
+      end
+      associated_instance.save!
+
+      user.destroy
+      associated_instance.reload
+    end
+
+    it { associated_class.find_by_id(associated_instance.id).should == associated_instance }
+    it "should keep the current user on all associations" do
+      associations.each do |association|
+        associated_instance.send(association).should == user2
+      end
+    end
+    it { associated_instance.journals.first.user.should == substitute_user }
+    it "should update the first journal" do
+      associations.each do |association|
+        associated_instance.journals.first.changes[association.to_s + "_id"].last.should == substitute_user.id
+      end
+    end
+    it { associated_instance.journals.last.user.should == user2 }
+    it "should update the last journal" do
+      associations.each do |association|
+        associated_instance.journals.last.changes[association.to_s + "_id"].first.should == substitute_user.id
+        associated_instance.journals.last.changes[association.to_s + "_id"].last.should == user2.id
+      end
+    end
+  end
+
+  describe "WHEN the user updated a cost object" do
+    let(:associations) { [:author] }
+    let(:associated_instance) { Factory.build(:variable_cost_object) }
+    let(:associated_class) { CostObject }
+
+    it_should_behave_like "updated journalized associated object"
+  end
+
+  describe "WHEN the user created a cost object" do
+    let(:associations) { [:author] }
+    let(:associated_instance) { Factory.build(:variable_cost_object) }
+    let(:associated_class) { CostObject }
+
+    it_should_behave_like "created journalized associated object"
+  end
+end