diff --git a/app/models/box.rb b/app/models/box.rb
new file mode 100644
index 0000000..8e489df
--- /dev/null
+++ b/app/models/box.rb
@@ -0,0 +1,9 @@
+class Box < ActiveRecord::Base
+  belongs_to :owner, :polymorphic => true
+
+  #we cannot have two boxs with the same number to the same owner
+  validates_uniqueness_of :number, :scope => :owner
+
+  #<tt>number</tt> must be a integer
+  validates_numericality_of :number, :only_integer => true, :message => _('%{fn} must be composed only of integers.')
+end
diff --git a/db/migrate/004_create_boxes.rb b/db/migrate/004_create_boxes.rb
new file mode 100644
index 0000000..1d33a4d
--- /dev/null
+++ b/db/migrate/004_create_boxes.rb
@@ -0,0 +1,13 @@
+class CreateBoxes < ActiveRecord::Migration
+  def self.up
+    create_table :boxes do |t|
+      t.column :number, :integer
+      t.column :owner_type, :string
+      t.column :owner_id, :integer
+    end
+  end
+
+  def self.down
+    drop_table :boxes
+  end
+end
diff --git a/test/fixtures/boxes.yml b/test/fixtures/boxes.yml
new file mode 100644
index 0000000..c786b5e
--- /dev/null
+++ b/test/fixtures/boxes.yml
@@ -0,0 +1,10 @@
+# Read about fixtures at http://ar.rubyonrails.org/classes/Fixtures.html
+one:
+  id: 1
+  number: 1
+two:
+  id: 2
+  number: 2
+three:
+  id: 3
+  number: 3
diff --git a/test/unit/box_test.rb b/test/unit/box_test.rb
new file mode 100644
index 0000000..c42e14e
--- /dev/null
+++ b/test/unit/box_test.rb
@@ -0,0 +1,46 @@
+require File.dirname(__FILE__) + '/../test_helper'
+
+class BoxTest < Test::Unit::TestCase
+  fixtures :boxes, :blocks
+
+  def test_destroy
+    count = Box.count
+    assert Box.find(1).destroy
+    assert_equal count - 1, Box.count
+  end
+
+  def test_create
+    count = Box.count
+    b = Box.new
+    b.number = 2
+    assert b.save
+    assert count + 1,  Box.count
+  end
+
+
+  def test_number_format
+    b = Box.new
+    b.number = "none"
+    assert !b.valid?
+    assert b.errors.invalid?(:number)
+
+    b = Box.new
+    b.number = 10.2
+    assert !b.save
+
+    b = Box.new
+    b.number = 10
+    assert b.save
+
+  end
+
+  def test_unique_number
+    assert Box.delete_all
+    assert Box.create(:number => 1)  
+   
+    b = Box.new(:number => 1)
+    assert !b.valid?
+    assert b.errors.invalid?(:number)
+  end
+
+end
--
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