I had the same thing with Hirevue assessments and never figured it out, but anywhere which sent me an automated coding test I at least got onto technical interviews on, also I got a perfect CodeSignal general coding test score.

Basically they’re automatically marked, and are looking for speed and correctness - not so much code quality, so if you use something like scala where the standard library is pretty expansive and you can just chain map/fold/filter that will usually work pretty well, they also usually give you the range of valid inputs, so you can see if it’s going to time out by checking the time complexity fits then running a test input at the top end of this.

Beyond that, the problem statements are usually asking for something that can be done in a few minutes at most, but are full of fluff so working in filtering that out may be the most helpful thing for increasing speed.