The way `make test` works is that all output is saved to a file for (optional) later inspection -- even for tests that pass. This makes it possible for tests to print a bunch of random information e.g. how many packest/second they achieved. This means it's okay/encouraged to make verbose printouts in test code because the user only sees if it they go looking.

This is redirected to a file on the Unix shell level. I suppose in Lua there is also a stdout variable that can be modified to redirect print() etc?