It depends on labs you apply. In my case, I had to talk with PIs, solve one problem set, do a presentation. All steps were quite straightforward and not hard
Fairly standard, spoke directly to the PI of the lab I was interested in and was asked about past lab experience, familiarity with the field the lab was part of, and comfort with various wet lab skills.
The process took 2 weeks. I interviewed at Institute for Systems Biology (Seattle, WA) in July 2020
Interview
I was asked to submit coding samples and write a one-page summary discussing potential research ideas that could be of interest. Additionally, I was asked to present one of my papers or any other work of my choosing.