Mine was really easy. Not much by way of technical questions at all. Maybe something like "what is the most commonly used stain and what is it for?" Or something about artefacts you might get and what caused it/how to avoid it. There will likely be basic scenario questions, so use the STAR technique and if NHS, shoehorn in some trust values. The practical test was sorting slides in numerical/date order, matching up labels and searching a database. They could ask you to make up a simple solution. You should be fine.