Comment by anonymars

We ask of every candidate. At least half the time, I wish I'd done so before getting invested in the "experience" portion, when that ends up not actually translating to ability (and believe me, I am trying to help them to succeed)

The beauty is, even a simple exercise answered quickly like "sum of integers" provides ample opportunity to learn a lot about how they think.

Start digging in to testability, requirement changes, etc. Change it to a rolling sum (producing a sequence instead of a single value). Do they use an array or an iterator? Do they output straight to the console, or produce an actual function? Could the numbers come from other sources (database, queue, etc)? What might the tradeoffs be? If there's something they are unfamiliar with, are they quick on the uptake if you explain it? And so on.