I'm not sure about this. I think this test is failing because the file is declared to be `UTF-8`, so when ruby parses it, it will read the `UTF-8` encoded representation of `ｵﾈ`. For example:

<pre>
$ cat test.rb
# -*- coding: utf-8 -*-
puts "ｵﾈ".encoding
$ ruby test.rb
UTF-8
</pre>

So when you call force_encoding, it's corrupting the string, and subsequent normalization will fail. Or was that the intention, to make it so the conversion would fail?