test: use ES6 classes instead of util.inherits
As part of the ongoing refactoring to ES6, I replaced many occurrences of util.inherits
within our unit tests with ES6 classes, plus some other minor changes to make the code more readable.
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