There are loads of those tests around especially in public sector admin jobs for some reason.
They will probably give you a list of ten things you need to do and you need to rank them in the order you would do them. So list will look this......
1. Book a venue for the office Christmas party 2. Evacuate the office because the building is on fire 3. Print off papers for meeting at 4pm 4. Return call to Chief Executive's PA regarding emergency safeguarding meeting
Answer will be... 2, 4, 3, 1
It will probably be about 20 minutes. They're testing you to see whether you can think on your feet and prioritise. It's not rocket science.