To really drive home the above 👆 point that 100% test coverage does not mean ‘bug free’, just found a bug in JSDB¹ 5.0.0 where running JSON.stringify() on a complex custom object (actually: the automatic Proxy of the custom object created by JSDB) results in an error.
Already have a failing test and about to implement fix.
(It’s at this point where the test harness is invaluable.)