Make sure 'update-gems' is called in the make process
As described among else in bug #9869, minitest was removed as a default gem.
It can be installed with
but I had to do that by hand. It should be done automatically (e.g. at least for make test and so on), or there should be a warning when testing without it.
P.S.: I still don't understand why we removed all testing libraries from a default installation; getting something out of the box that is reasonably complete is an important feature of a programming language, and a testing library is a very important part of that.