A written test. Lot's of questions. Better to spend less time on nasty problems.

The interview process consists of multiple stages with hard quantitative bars to be met. After CV screening, they send you their proprietary online assessment of 10 MC. Some questions seem unusual, some are intentionally tricky, but most are similar to standard quant brainteasers and you can pass if you have really grinded through standard material. Then, there is an online interview with a quant which will ask you technical questions in barrage. The bar probably depends on your answers' grades and how many questions you can answer. I did not expect some questions, so I was caught unprepared and I fumbled spectacularly.