As FFF said what a good and difficult question.
If the checker is very experienced then they will have seen it all before (as it were) and so will not find it too difficult to make the call.
BUT if the checker is pretty new to the game and I was briefing or tasking the checker I would say something on the lines of
“So and so needs a check ride. Find out what he intends to do with the aircraft after his checkout. Then ask him what he expects to show you for his checkout. If he has no clear plan and does not volunteer something on the lines of a couple of circuits, throttle chop somewhere, bit of stalling (as a minimum) then that is your first warning sign that this guy needs watching. If his proposed sortie plan does NOT satisfy you then say to him - OK well we normally do a bit more than that, so I would like to brief you on what we need to do. Then you brief the trip you want. In other words you have to really take charge. From the time you start the engine to the time you turn it off stay alert. Assume he is about to let you down and don’t be afraid to take control if he does things in a different way from the one you know. If you have to take over once you are flying the aircraft have a gentle conversation and try and find his reasons for not doing it your normal way. As well as staying alert never assume that the next thing he does will be OK just because the last bit was fine. Afterwards if you have any real doubts about him come and see me so that we can discuss things”
Remember if you do not have stacks of experience youself then the ONLY way you can tackle the decision is to ask yourself whether he is as safe and sensible as you. If you are not sure the answer is yes get help.