Plenty of people picture acceptance testing as a few business users clicking through the finished system in the last week before release, which makes a certificate in it look like a tester's badge. The ISTQB Certified Tester Acceptance Testing (CT-AcT) syllabus treats it differently: acceptance criteria are written while requirements are still being shaped, and product owners and business analysts sit the paper alongside testers. It is 40 questions in 60 minutes, with 26 needed to pass.

Is acceptance testing really a last-week activity, and who is this certificate for?
The myth has a grain of truth. Acceptance testing is the level at which a customer or user decides whether a system is ready to be released, and in a strictly sequential project that decision does arrive late. What the syllabus adds is that almost everything which makes the decision sound happens much earlier. Someone has to turn a business need into a requirement, the requirement into measurable acceptance criteria, the criteria into tests, and all of it has to be understood by people who will never read a test script. If that early work is vague, the late test is a formality and the surprises arrive after go-live.