add a test for [ruby-dev:26127].

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@8535 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/set.rb

@@ -1060,6 +1060,8 @@ class TC_Set < Test::Unit::TestCase
 #    assert_equal(set2, set1)
     assert_equal(set2, set2.clone)
     assert_equal(set1.clone, set1)
+
+    assert_not_equal(Set[Exception.new,nil], Set[Exception.new,Exception.new], "[ruby-dev:26127]")
   end
 
   # def test_hash