diff --git a/ChangeLog b/ChangeLog
index f9fc87042b..87e44fe083 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Sat Jul 21 14:06:41 2012  Shota Fukumori  <sorah@tubusu.net>
+
+	* lib/test/unit.rb: warn when test_* method is redefined.
+	  Patch by mame (Yusuke Endoh). [Feature #2643] [ruby-core:27790]
+
+	* test/testunit/test_redefinition.rb: Test for above.
+
+	* test/testunit/test4test_redefinition.rb: Ditto.
+
 Sat Jul 21 08:41:14 2012  Eric Hodel  <drbrain@segment7.net>
 
 	* lib/logger.rb:  Updated example in Logger comment to match other
diff --git a/lib/test/unit/testcase.rb b/lib/test/unit/testcase.rb
index 02f0f97987..11f34b6f51 100644
--- a/lib/test/unit/testcase.rb
+++ b/lib/test/unit/testcase.rb
@@ -20,6 +20,17 @@ module Test
       def self.test_order
         :sorted
       end
+
+      Methods = {}
+
+      def self.method_added(name)
+       return unless name.to_s[/\Atest_/]
+       Methods[self] ||= {}
+       if Methods[self][name]
+         warn("test/unit warning: method #{ self }##{ name } is redefined")
+       end
+       Methods[self][name] = true
+      end
     end
   end
 end
diff --git a/test/testunit/test4test_redefinition.rb b/test/testunit/test4test_redefinition.rb
new file mode 100644
index 0000000000..72c4cb225a
--- /dev/null
+++ b/test/testunit/test4test_redefinition.rb
@@ -0,0 +1,11 @@
+require 'test/unit'
+
+class TestForTestRedefinition < Test::Unit::TestCase
+  def test_redefinition
+    skip "do nothing (1)"
+  end
+
+  def test_redefinition
+    skip "do nothing (2)"
+  end
+end
diff --git a/test/testunit/test_redefinition.rb b/test/testunit/test_redefinition.rb
new file mode 100644
index 0000000000..612661ee65
--- /dev/null
+++ b/test/testunit/test_redefinition.rb
@@ -0,0 +1,13 @@
+require 'test/unit'
+
+class TestHideSkip < Test::Unit::TestCase
+  def test_hideskip
+    test_out, o = IO.pipe
+    spawn(*@options[:ruby], "#{File.dirname(__FILE__)}/test4test_redefinition.rb", out: File::NULL, err: o)
+    o.close
+
+    assert_match /^test\/unit warning: method TestForTestRedefinition#test_redefinition is redefined$/,
+                 test_out.read
+    test_out.close
+  end
+end