Seems you figured out how to run Quidem tests. How could the documentation be improved? Should we add more documentation to the QuidemTest class?
In the end the page at https://calcite.apache.org/docs/howto.html#running-integration-tests was the one that got me on the right track. Via trial-and-error I ended up modifying misc.iq and running the following, because it was quick and yielded the result and diff I needed:
>mvn -f core/pom.xml verify -Pti -Dtest=Quidem
although I'm not sure the -Dtest=... does what I think it does, because when the .iq test begin to pass then many more tests run, so I believe I was just lucky in the order. Also, the actual .iq expected result and plan I copy-pasted them from the mvn diff output, I did not locate any output file in core/target to copy from.
As for what to improve, I think the calcite.apache.org HOWTO is the best resource to get the ball rolling. Had the QuidemTest class contain detailed explanation exactly step by step what to do, I would still probably not stumble upon it, and not know where to start.