I'm working on a questionnaire which contains mandatory questions such as Date of Birth (three different drop downs are provided), plus a check box and some Yes/No type questions.

Without answering these questions, users are not supposed to be allowed to move to the checkout page, however, orders *are* being created by live users, yet these order have DOB null and other mandatory answers are also null (unanswered).

When I asked live users how they got past the restrictions, they just reply that they answered all the questions on the form.

What is the other way to test this questionnaire?