Another approach is to change the responsibility.
My feeling is that tests in the TESTING package should be modifiable by the maintainer of
the TESTED package, with both packages suspended if the two maintainers cannot agree. We
need to be able to move forward when legacy behaviour is outdated or just plain wrong. Or,
in the case that I find affects me, when improvements in iterative schemes change iterates
slightly. My guess is that Duncan's example is a case in point.
I doubt this will ever occur, as it doesn't seem to be the R way. However, I do know that
improvements in methods are not going to CRAN in some cases.
JN