Introduce `assert()` into some test.
./test/functional/test_runner.py thattest.py
ls -al test/tmp/lastfailure
./test/functional/combine_logs.py test/tmp/lastfailure
./test/functional/test_runner.py thattest.py
head test/tmp/lastfailure/test_framework.log # verify the symlink updated by looking at the test directory name