So here is the reason to add the spec is as follows, I don't understand why we need to use binread?

MRI
```
 IO.write(@filename, 'hello', :encoding => 'UTF-16') # => 12
 IO.write('op', 'hi', :mode => "w", :encoding => Encoding::UTF_32LE) # => 8
```

RBX

```
IO.write('op', 'hello', :encoding => 'UTF-16') # => 12
IO.write('op', 'hi', :mode => "w", :encoding => Encoding::UTF_32LE) # => 2
```