Refactored and rewrote a >100k LOC expert system in the medical field. This was a single Java source file with one long if else tree. Everything was hard coded

Refactored and rewrote a >100k LOC expert system in the medical field. This was a single Java source file with one long if else tree. Everything was hard coded constants. It was like "if (setting.equals(foobar)) { if (a == 1 && b == 10 && ...) { sendAlert(); } }" There was no testing and no documentation of the feature sets involved. Rewrote the code in under 10k LOC, huge cost and performance improvements were had, and the feature set was documented. Other engineers could look at the code and maintain it. Got the critical sections of the expert system to 100% branch coverage. Had to fight against other engineers who were saying "100% coverage is bad! I read that on medium!" I just did it anyway due to my own ethical concerns of writing bad software in this area and it only took me ~4hr more to get from 80% to 100% critical path code coverage. Some of the most stressful software I worked on. I added in shit loads of logging to make sure that if anything did go wrong we'd find out what happened. At some point someone wasn't notified about something the expert system was supposed to catch. I felt like I was going to faint because this meant someone was seriously hurt. Unfortunate twist: my code worked correctly. The system on the other end who was supposed to send the alert (maintained by the "100% coverage is bad" guy) died. Very unfortunate. The other engineer didn't feel bad about it at all. I think about this a lot when I'm speaking to engineers. I use it as a litmus test for who I really enjoy working with. If they read a medium article and can't apply critical thinking to identify if it relates to their circumstances or not. Also, attempting to find out if they refuse to hear out a coworker.