"Employers hiring technical writers want candidates with the technical knowledge and written communication skills to simplify complex concepts. In an interview, be prepared to discuss your writing experience and provide an example of a time you explained a difficult idea to a group or classroom. Your interviewer may also quiz you on technical concepts or ask you to engage in a written exercise."
I was given a writing test. The test included three poorly organized technical writing passages that I was instructed to rewrite. Great idea to add this and something I have never seen in a technical writing interview. Typically you're just asked for samples and those are used to evaluate your ability as a writer.
I rewrote each of the passages, reorganizing the content and attempting to apply a minimalist style.