test_transcode.rb: add messages

* test/ruby/test_transcode.rb (test_valid_dummy_encoding): add
  assertion messages and suppress a warning.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44477 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_transcode.rb

@@ -2085,10 +2085,10 @@ class TestTranscode < Test::Unit::TestCase
     bug9314 = '[ruby-core:59354] [Bug #9314]'
     assert_separately(%W[- -- #{bug9314}], <<-'end;')
     bug = ARGV.shift
-    result = assert_nothing_raised(TypeError) {break "test".encode(Encoding::UTF_16)}
-    assert_equal("\xFE\xFF\x00t\x00e\x00s\x00t", result.b)
-    result = assert_nothing_raised(TypeError) {break "test".encode(Encoding::UTF_32)}
-    assert_equal("\x00\x00\xFE\xFF\x00\x00\x00t\x00\x00\x00e\x00\x00\x00s\x00\x00\x00t", result.b)
+    result = assert_nothing_raised(TypeError, bug) {break "test".encode(Encoding::UTF_16)}
+    assert_equal("\xFE\xFF\x00t\x00e\x00s\x00t", result.b, bug)
+    result = assert_nothing_raised(TypeError, bug) {break "test".encode(Encoding::UTF_32)}
+    assert_equal("\x00\x00\xFE\xFF\x00\x00\x00t\x00\x00\x00e\x00\x00\x00s\x00\x00\x00t", result.b, bug)
     end;
   end
 end