When I started my first project I didnt know that ever I would be assigned the responsibility of a Tester. I always knew that the Business Analyst is active and important in the first few phases of the software development lifecycle. And to perform the tasks in other phases like development and testing, one requires a skill for that particular discipline. But then in one of my projects I was asked to perform this task as some of the testers had left the project and it was getting difficult to hire the right people at this point of time. So the business analyst team was expected to step in and assist the testing team and complete the project withing budget and on time.

First I was intimidated to put my foot in the door. Later it all made sense to me as I had to check that the application for which we documented the set of detailed functional requirements is meeting those requirements or not. I designed manual test cases based on the use case spefications and use case diagrams which our team had created and created the coverage analysis document.While designing the test cases I already had the possible test scenarios as I was well versed with the requirements and the business rules which helped me to sail through this role smoothly.

I am not saying that every business analyst can be a Tester. But the point I am trying to make here is that a Business Analyst could be expected to step in a role of tester but not vice versa.
Please share your experiences and also the besy way you handled this when you came across this situation for the first time.