Just one more note specifically for this: adding new tests won’t slow down the build additionally!
The slow things are “already there”. The Simulator won’t boot slower because you add new tests, it’ll take the same amount of time (roughly).
Of course a larger code takes more time to compile, but that’s the same as on your Mac, the diff is about the same as on your Mac (if you do a clean build right now vs with a more complex code later).