Sometimes I've needed a 'deep compare' for ActiveRecord objects. This method returns a Hash containing the objects attributes plus the attributes from the first layer of relationships. After using #except to exclude attributes that should change, I can assert_equal to compare.

attr_tree.rb

class ActiveSupport::TestCase

  def attr_tree(obj)
    tree = obj.attributes.except("id")
    obj.class.reflections.each do |refl_name,refl|
      refl_key = refl_name.to_s
      case refl.macro
      when :belongs_to, :has_one
        tree[refl_key] = (o = obj.send(refl_name)) && o.attributes
      when :has_many, :has_and_belongs_to_many
        tree[refl_key] = []
        obj.send(refl_name).each{|o| tree[refl_key] << o.attributes.except("id")}
      else
        raise "Unhandled reflection #{refl.macro} :#{refl_name}"
      end
    end
    tree
  end
end