We'd like to run the tests in "make test" in parallel, so that we can actually utilize all cores in multi-core machines.
testr allows us to run tests in parallel, and we've already got most of the infrastructure to do that in place (selftest --list, selftest --load-list, .testr.conf).
The main thing that is preventing us from running testr are the fact that tests currently have to be run in a specific order, which we can't do with multiple workers.
Fixed in Samba 4.9, 4.10 and 4.11 with increasing use of gitlab and the split up of the test environment.
Not quite the fix asked for, but a practical step forward.