Today I learned something, that probably everyone but me already knew. I wanted to run only a subset of ruby-core’s unit tests, because running them all takes quite a while. I didn’t find a way to do it in the README, and it took me quite a while of googleing to find this post.
To summarize, instead of just running
make test-all, you can for example
make test-all TESTS="csv/" to run all tests in
test/csv/. You can
even be more specific and pass a test file, to run only that.