Ruby Metaprogramming

meta_animals.rb

#
# Regarding https://gist.github.com/1180947
# 
require 'test/unit'

# Example classes
class Animal; end

class Dog < Animal
  attr_accessor :name

  def initialize(name=nil)
    self.name = name
  end
end


# Tests
class TestAnimal < Test::Unit::TestCase

  def test_register_property
    dog = Dog.new

    Dog.class_eval do
      attr_accessor :no
    end

    assert_respond_to dog, :no
  end

  def test_register_method
    beethoven = Dog.new('Beethoven')

    Dog.class_eval do
      def speak
        "Hello I'm #{name}"
      end
    end

    assert_respond_to beethoven, :speak
    assert_equal "Hello I'm Beethoven", beethoven.speak
  end

  def test_extend_with_something_that_kinda_looks_like_a_hash_map
    beethoven = Dog.new('Beethoven')
    
    Dog.class_eval do
      {
        :bark     => proc { "Woof! Woof!" },
        :is_named => proc { |name| self.name == name }
      }.each do |method,block|
        self.send(:define_method, method, block)
      end
    end

    assert !beethoven.is_named("Johnny")
    assert_equal 'Woof! Woof!', beethoven.bark
  end

  def test_inheritance
    beethoven = Dog.new('Beethoven')

    Animal.class_eval do
      def foo
        'bar'
      end
    end

    # Couldn't exactly figure out why the PHP tests were
    # assetFalse(); was that just to make the tests pass?
    assert_respond_to beethoven, :foo
    assert_not_equal Animal, Dog
  end

end

The last test in my gist, should assert that the Dog and Animal Classes do not have the same MetaClass, so that
methods added to the Dog class do not end up accessible from the Animal class.

Though this test fails in the current implementation. Maybe I'll look into it when I've more time.