class Test::Unit::TestCase

  def self.klass
    self.name.chomp("Test")
  end

  def self.creator(options={})   
    define_method("create_#{self.klass.underscore}") {|*args| 
    opts = args.first || {}
    klass.constantize.create(options.merge(opts)) }
  end

  def self.default_creation_test
    define_method("test_should_create_#{klass.underscore}") {
      assert_difference klass.constantize, :count do
        object = send("create_#{self.klass.underscore}")
        assert !object.new_record?, "#{object.errors.full_messages.to_sentence}"
      end
    } 
  end

  def self.erroneous_creation_test(field, value)
    define_method("test_should_not_create_on_erroneous_#{field.to_s}") {
      assert_no_difference klass.constantize, :count do
        object = send("create_#{self.klass.underscore}", {field => value})
        assert_not_nil object.errors.on(field)
      end
    }
  end


# ...
end