test: increase coverage of string-decoder
Add normalizeencoding's test. normalizeEncoding: https://github.com/nodejs/node/blob/master/lib/string_decoder.js#L9 Make use of Arrow Function.
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines
Affected core subsystem(s)
test