@jan-cerny In this draft I've only changed a handful of compound tests, but we probably should do that to all of them. What do you think?

IIUC most of the test functions don't return any return value, they rely on that the set -e will cause that once any command in the function returns non-zero value the test will exit and fail. This is the case for all the grep, assert_exists and similar calls. So if you remove set -e the test will start passing permanently.