My experience is the opposite.  Spend time simplifying your thinking, and it stays simple.  But it is very, very easy to start overthinking things and then you go down a rabbit hole.<p>Consider this for an example.  If you&#x27;re testing per session behavior, then you can just use a session cookie.  If you&#x27;re testing logged in behavior, you can use the login id.  You&#x27;ve just covered most of the things you want to test.<p>When you start worrying about cross-device both logged in and not, then you have a world of pain.  So treat it as an identity problem, throw away all of the users you find questionable, and work with that.  And yes, this is a pain, which is why you do it as seldom as you can!