My new job's codebase has zero tests. Raise it in month one or wait?

Four weeks in, team of five, and the repo has no tests at all. I've been quietly adding a few around the code I touch, but I don't want to come across as the new person telling everyone they're doing it wrong. My manager seems relaxed, and nothing in onboarding mentioned it. Would you bring it up, or let it come up naturally on a ticket?