use less ruby in tests

use less ruby in tests and hopefully eliminating last place where 'Errno::EBADF: Bad file descriptor' happened.

UT run locally
BTW, these `.rz` files are showing up as text files which could cause problems on platforms which change line-endings on checkout. Suggest adding `*.rz binary` to the projects top-level `.gitattributes` and make sure that existing checked in `.rz` files are flagged as binary in git.