forgot to add test_undef.rb in the previous revision.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@25832 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_undef.rb

@@ -0,0 +1,37 @@
+require 'test/unit'
+
+class TestUndef < Test::Unit::TestCase
+  class Undef0
+    def foo
+      "foo"
+    end
+    undef foo
+  end
+
+  class Undef1
+    def bar
+      "bar"
+    end
+  end
+
+  class Undef2 < Undef1
+    undef bar
+  end
+
+  def test_undef
+    x = Undef0.new
+    assert_raise(NoMethodError) { x.foo }
+    y = Undef1.new
+    assert_equal "bar", y.bar
+    z = Undef2.new
+    assert_raise(NoMethodError) { z.foo }
+  end
+
+  def test_special_const_undef
+    assert_raise(TypeError) do
+      1.instance_eval do
+        undef to_s
+      end
+    end
+  end
+end