While not always true for everyone, there seems to be a majority (anecdotal from others I've spoken with) that experience faster Jest runs with --maxWorkers=50% (or some similar setting) than without it set or setting it to 100%.
My personal experience with an 8 core machine is that if I don't set --maxWorkers then I will have 7 concurrent workers running (as expected coreCount - 1) and it will run slower than if I set --maxWorkers=50% which creates 4 concurrent workers.
Why this is happening doesn't make sense to me. i.e. allocating more resources slows this down instead of speeding it up. Can anyone explain this?