FWIW, I have a SRFI-64 implementation whose code-base and default test runner is somewhat cleaner than the upstream one:
https://github.com/TaylanUB/scheme-srfis/tree/master/srfi/64
(All actual code is in the *.body.scm files. Others are R7RS library
wrappers.)
It sounds like using a custom test runner was the right thing in your
case though, so the default test runner of the implementation is
probably unimportant.
- Taylan
