What would you do if you end up with unclear requirements or requirements are not available?

In this scenario, your knowledge of application plays a big role. I would start to do some random testing to understand what is being asked and try to discover to get an idea, so I can start writing scripts. Then I will also check out our meeting notes, emails, and discussions. On top of that, look for wireframes which might give me an idea but overall my common sense and experience plays a part here and also I would think from a customer’s perspective. Also if BA is available to clarify with them as well.