The interviewers from the web design team look at your portfolio and ask about your knowledge of design and development tools such as Adobe Creative Suite, Figma, etc. Usual questions to gauge proficiency and to see how your workflow aligns with theirs.
I was also asked to do an assessment (unpaid) of developing a homepage from a design file on a testing environment exclusively using the Divi builder. After completion, I received no feedback from the web design team regarding the work, and only found out about them not moving forward with my application from the admin person who posted the job listing about a week after submitting the assessment.