Creating a Pre-test

In class today we created a pre-test for our students. We had yet to meet these students and we were ALREADY thinking of how to create a test to assess their prior knowledge. I was confused on how to design this test with out actually meeting these students. Our class was divided up into four groups and each group had a different topic that they were to create questions for. We had JUST met our group partners and I didn't really know any of them so this was all new for me. We were not sure what to ask the students. We came up with some questions in the end that we were still unsure about. I found this to be difficult and I wasn't sure how we were to use it in the class.

UPDATE! 
So after we had our field work we had asked the students to fill out another assessment test. This was a post-test. When my group started meeting and creating our lesson plan I understood the pre-test. I understood the reason for why we needed to assess their knowledge of where they are in their learning. We needed to know where to start teaching! This I just didn't think of until we had to create a lesson plan and we were unsure of what they had known.