While trying to diagnose a tricky car not starting problem I was asked to check if the spark plugs were firing at all.
I've found plenty of resources on inspecting the condition of spark plugs after removing them, and to do with diagnosing misfiring spark plugs, but not a test for a simple yes-no, are they firing at all or aren't they.
This is a first generation (1998) Toyota RAV4, which I believe means they are the coil-on type (could be wrong). They're deep set in a straight cylinder.
If possible, I'd like to test if they're firing without removing them, which would require specialist tools I don't have easy access to and might result in me damaging them.