Give the candidates a non-trivial problem, which might take a few days to complete. Everything documented and checked into github. Call them for interviews and review design/code with them. Make sure it was not all copy-pasta and someone else didn't write it for them.
To make sure of that, introduce a slight variation in spec and ask them to do it on the spot.
This way, you get to review their entire development process, How they approach problems, code quality, unit tests, code performance , usage of source control system, CI/CD usage etc. At this point you will know for sure if you want them or not (They might also know they want to work for you or not .. :-). )