I'm also curious about nootropics that improve focus and or mood, which seems to difficult to measure. Coffee and aderall work in this category, but I wonder how you test other potential nootropics for those effects.

Focus is sometimes tested by giving people a task and introducing distracting influences in a controlled manner. I recall nicotine being tested on children in this way (it works about as well as Adderall if memory serves me.) But there isn't too much incentive for people to formally research this kind of thing for most nootropics so a lot of the time we just have ad hoc anecdotal reports to go by.

Modafinil is better for boosting mood than caffeine or adderall, especially in as much as it tends to provoke less agitation. The effect on focus is not quite as pronounced as with the amphetamine. This is sometimes considered a good thing when the overfocus is detrimental (eg. when socialising or exposed to TvTropes.)

Selegeline also improves both focus and mood - in a more subtle way over periods of weeks (irreversible MAOB inhibition doesn't 'rebound' after a few hours).

For mood specifically try Phenylethylamine while you are taking selegeline (carefully!) or use phenibut.

Are there any cognitive tests that can measure creativity?

I don't know how reliable it would be, but you can try a book of "lateral thinking puzzles."