moving files around a bit

koans/about_open_classes.rb

@@ -0,0 +1,45 @@
+require 'edgecase'
+
+class AboutOpenClasses < EdgeCase::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 even?
+      (self % 2) == 0
+    end
+  end
+
+  def test_even_existing_built_in_classes_can_be_reopened
+    assert_equal __, 1.even?
+    assert_equal __, 2.even?
+  end
+
+  # NOTE: To understand why we need the :: before Integer, you need to
+  # become enlightened about scope.  
+end