gistfile1.rb

class Test::Unit::TestCase  
  def self.should_validate_associated(*associations)
    klass = self.name.gsub(/Test$/, '').constantize
    context "#{klass}" do
      associations.each do |association|
        should "validate #{association} association" do
          assert klass.new.respond_to?("validate_associated_records_for_#{association}")
        end
      end
    end
  end
end

### usage example
# model
class Product < ActiveRecord::Base
  belongs_to :discount
  belongs_to :shop

  validates_associated :discount
  validates_associated :shop
end

# test
class ProductTest < ActiveSupport::TestCase
  should_validate_associated :discount
end

# you test multiple associations just like other shoulda macros
class ProductTest < ActiveSupport::TestCase
  should_validate_associated :discount, :shop, :user
end