Current progress

koans/about_open_classes.rb

@@ -0,0 +1,45 @@
+require File.expand_path(File.dirname(__FILE__) + '/neo')
+
+class AboutOpenClasses < Neo::Koan
+  class Dog
+    def bark
+      "WOOF"
+    end
+  end
+
+  def test_as_defined_dogs_do_bark
+    fido = Dog.new
+    assert_equal __, fido.bark
+  end
+
+  # ------------------------------------------------------------------
+
+  # Open the existing Dog class and add a new method.
+  class Dog
+    def wag
+      "HAPPY"
+    end
+  end
+
+  def test_after_reopening_dogs_can_both_wag_and_bark
+    fido = Dog.new
+    assert_equal __, fido.wag
+    assert_equal __, fido.bark
+  end
+
+  # ------------------------------------------------------------------
+
+  class ::Integer
+    def answer_to_life_universe_and_everything?
+      self == 42
+    end
+  end
+
+  def test_even_existing_built_in_classes_can_be_reopened
+    assert_equal __, 1.answer_to_life_universe_and_everything?
+    assert_equal __, 42.answer_to_life_universe_and_everything?
+  end
+
+  # NOTE: To understand why we need the :: before Integer, you need to
+  # become enlightened about scope.
+end