A/B testing can be as simple or as complex as you want. For example, you can conduct simple version tests where you compare the effectiveness of a new B version against an original A version. You can also conduct multivariate tests (MVT) where you compare the effectiveness of different combinations of changes. You could also test three or more variations simultaneously, called A/B/n testing. If you can change your codebase that modifies your user experience, there is a way to test it.