This is pretty silly thing to watch out for. Being a zealot about anything, especially something like unit tests, is certainly
not a good idea when searching for a good job. Setting aside the fact that whether unit tests exist and how they are managed often
does depend on the project/product/client (and the fact that many good web start-ups don't do unit testing for very good reasons), it's just a bad idea to discount a company based on some technical aspects you may disagree with (especially if you only have a few years of experience and really don't have a strong foundation for evaluating this).
Instead, you are looking for good co-workers, good management, a comfortable work environment, and a compelling or at least interesting-enough business. You are not looking for a company that merely subscribes to your pet programming philosophy.