That's how every one of these tools works, that’s the whole point of using them: you only call them when you’re going to actually show the variation to the user. If you’re running a test that modifies the homepage only, you shouldn’t be calling that decision method in, say, your global navigation code that you show everyone. Or, for instance, if your test only affects how the header looks for subscribers, you have to put an outer if statement “if subscriber“ before the “if test variation.“ How else would it correctly know exactly who saw the test?