I can run every test on my machine if I want. It would be a manual effort, but wouldn't be hard to automate if I cared to try. However it would take about 5 days to finish. It isn't worth it when such tests rarely fail - the CI system just spin them off to many AWS nodes and if something fails then run just that test locally and I get results in a few hours (some of the tests are end to end integration that need more than half an hour).

Like any good test system I have a large suite of "unit" tests that run quick that I run locally before committing code - it takes a few minutes to get high code coverage if you care about that metric. Even then I just run the tests for x86-64, if they fail on arm that is something for my CI system to figure out for me.