[OhHeyItsE]

I've found that companies that are serious about this will offer some form of compensation (gift card, etc)

[chrisco255]

They shouldn't have to compensate you for a trivial exercise to prove your ability. This isn't production-code type of problem, these are usually toy problems just designed to show you can code and you care about quality.

[jakebasile]

Something that takes more than a couple hours is no longer trivial.