I had a great pleasure to take part in the JAVIPS online 2020.
How a developer can tell if the system is sick just by taking a look at the input and the output? If you’d like to know that (plus you like standup comedy), come and see! The treatment is safe ;-) One approach to get familiar with a system is a long and intense reading the manual (and to run an eye over the source code sometimes). Another approach is to take a deep dive into the data model (often in the DB) and to surf the user interface.