I think having tests in your portfolio would impress an interviewer. It shows an attention to detail and a depth of knowledge. Some work environments take testing very seriously. In some environments you don’t even start coding until the unit tests are written.
But there are a lot of things to learn. You have to decide where you want to spend your time. But having some exposure to basic unit testing, I think that would impress someone. Where I work, people won’t even look at a PR unless there are tests. You can just do it on a few projects, maybe. I don’t think they expect you to be an expert, but some exposure would be good.