Should fail: F8 87 BF BF BF # Overlong
Should fail: FC 83 BF BF BF BF # Overlong
Should pass: EF BF BE # U+FFFE (invalid unicode, valid UTF-8)
-Should fail: EF BF BF # U+FFFF (invalid unicode, valid UTF-8)
+Should pass: EF BF BF # U+FFFF (invalid unicode, valid UTF-8)