I have problems to get rspec running properly to test validates_inclusion_of my migration looks like this:

class CreateCategories < ActiveRecord::Migration
  def self.up
    create_table :categories do |t|
      t.string :name
      t.integer :parent_id
      t.timestamps
    end
  end

  def self.down
    drop_table :categories
  end
end

my model looks like this:

class Category < ActiveRecord::Base
  acts_as_tree

  validates_presence_of :name
  validates_uniqueness_of :name
  validates_inclusion_of :parent_id, :in => Category.all.map(&:id), :unless => Proc.new { |c| c.parent_id.blank? }
end

my factories:

Factory.define :category do |c|
  c.name "Category One"
end

Factory.define :category_2, :class => Category do |c|
  c.name "Category Two"
end

my model spec looks like this:

require 'spec_helper'

describe Category do
  before(:each) do
    @valid_attributes = {
      :name => "Category"
    }
  end

  it "should create a new instance given valid attributes" do
    Category.create!(@valid_attributes)
  end

  it "should have a name and it shouldn't be empty" do
    c = Category.new :name => nil
    c.should be_invalid
    c.name = ""
    c.should be_invalid
  end

  it "should not create a duplicate names" do
    Category.create!(@valid_attributes)
    Category.new(@valid_attributes).should be_invalid
  end

  it "should not save with invalid parent" do
    parent = Factory(:category)
    child = Category.new @valid_attributes
    child.parent_id = parent.id + 100
    child.should be_invalid
  end

  it "should save with valid parent" do
    child = Factory.build(:category_2)
    child.parent = Factory(:category)
    # FIXME: make it pass, it works on cosole, but I don't know why the test is failing
    child.should be_valid
  end
end

I get the following error:

'Category should save with valid parent' FAILED Expected #<Category id: nil, name: "Category Two", parent_id: 5, created_at: nil, updated_at: nil> to be valid, but it was not Errors:

Parent is missing

On console everything seems to be fine and work as expected:

c1 = Category.new :name => "Parent Category"
c1.valid? #=> true
c1.save #=> true
c1.id #=> 1
c2 = Category.new :name => "Child Category"
c2.valid? #=> true
c2.parent_id = 100
c2.valid? #=> false
c2.parent_id = 1
c2.valid? #=> true

I'm running rails 2.3.5, rspec 1.3.0 and rspec-rails 1.3.2

Anybody, any idea?