diff --git a/ChangeLog b/ChangeLog
index 9b0fb6b27f..b130e2c3ee 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Jan 12 16:09:09 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
+
+	* test/ruby/enc/test_casing_options.rb: Tests for option
+	  parsing/checking for upcase/downcase/capitalize/swapcase
+	  (see r53503; with Kimihito Matsui)
+
 Mon Jan 12 16:03:03 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
 	* string.c: Added option parsing/checking for upcase/downcase/
diff --git a/test/ruby/enc/test_casing_options.rb b/test/ruby/enc/test_casing_options.rb
new file mode 100644
index 0000000000..5f5e6173ae
--- /dev/null
+++ b/test/ruby/enc/test_casing_options.rb
@@ -0,0 +1,81 @@
+# Copyright © 2016 Kimihito Matsui (松井 仁人) and Martin J. Dürst (duerst@it.aoyama.ac.jp)
+
+require "test/unit"
+
+class TestCasingOptions < Test::Unit::TestCase
+  def assert_raise_functional_operations (arg, *options)
+    assert_raise(ArgumentError) { arg.upcase *options }
+    assert_raise(ArgumentError) { arg.downcase *options }
+    assert_raise(ArgumentError) { arg.capitalize *options }
+    assert_raise(ArgumentError) { arg.swapcase *options }
+  end
+ 
+  def assert_raise_bang_operations (arg, *options)
+    assert_raise(ArgumentError) { arg.upcase! *options }
+    assert_raise(ArgumentError) { arg.downcase! *options }
+    assert_raise(ArgumentError) { arg.capitalize! *options }
+    assert_raise(ArgumentError) { arg.swapcase! *options }
+  end
+
+  def assert_raise_both_types (*options)
+    assert_raise_functional_operations 'a', *options
+    assert_raise_bang_operations 'a', *options
+    assert_raise_functional_operations :a, *options
+  end
+
+  def test_option_errors
+    assert_raise_both_types :invalid
+    assert_raise_both_types :lithuanian, :turkic, :fold
+    assert_raise_both_types :fold, :fold
+    assert_raise_both_types :ascii, :fold
+    assert_raise_both_types :fold, :ascii
+    assert_raise_both_types :ascii, :turkic
+    assert_raise_both_types :turkic, :ascii
+    assert_raise_both_types :ascii, :lithuanian
+    assert_raise_both_types :lithuanian, :ascii
+  end
+
+  def assert_okay_functional_operations (arg, *options)
+    assert_nothing_raised { arg.upcase *options }
+    assert_nothing_raised { arg.downcase *options }
+    assert_nothing_raised { arg.capitalize *options }
+    assert_nothing_raised { arg.swapcase *options }
+  end
+
+  def assert_okay_bang_operations (arg, *options)
+    assert_nothing_raised { arg.upcase! *options }
+    assert_nothing_raised { arg.downcase! *options }
+    assert_nothing_raised { arg.capitalize! *options }
+    assert_nothing_raised { arg.swapcase! *options }
+  end
+
+  def assert_okay_both_types (*options)
+    assert_okay_functional_operations 'a', *options
+    assert_okay_bang_operations 'a', *options
+    assert_okay_functional_operations :a, *options
+  end
+
+  def test_options_okay
+    assert_okay_both_types
+    assert_okay_both_types :ascii
+    assert_okay_both_types :turkic
+    assert_okay_both_types :lithuanian
+    assert_okay_both_types :turkic, :lithuanian
+    assert_okay_both_types :lithuanian, :turkic
+  end
+
+  def test_operation_specific   # :fold option only allowed on downcase
+    assert_nothing_raised { 'a'.downcase :fold }
+    assert_raise(ArgumentError) { 'a'.upcase :fold }
+    assert_raise(ArgumentError) { 'a'.capitalize :fold }
+    assert_raise(ArgumentError) { 'a'.swapcase :fold }
+    assert_nothing_raised { 'a'.downcase! :fold }
+    assert_raise(ArgumentError) { 'a'.upcase! :fold }
+    assert_raise(ArgumentError) { 'a'.capitalize! :fold }
+    assert_raise(ArgumentError) { 'a'.swapcase! :fold }
+    assert_nothing_raised { :a.downcase :fold }
+    assert_raise(ArgumentError) { :a.upcase :fold }
+    assert_raise(ArgumentError) { :a.capitalize :fold }
+    assert_raise(ArgumentError) { :a.swapcase :fold }
+  end
+end