What role did you play in A/B testing — were you the customer or did you also do some hands-on work?

In A/B tests, I usually acted not only as the client, formulating hypotheses and test goals, but also participated in the preparation and implementation of the test. This included setting up the experiment in the A/B testing system, defining user segments, monitoring metrics, and analyzing results. Such an approach helps better understand technical limitations and respond more quickly to unexpected results.