I built a tool that reads modded Minecraft crash reports and tells you which mod killed the server. It passed every test I wrote and was still wrong about most real crashes. Here is what the real data taught me, in the order it hurt. Your own samples will lie to you I wrote the tool first and the test fixtures second. Six synthetic logs, one per failure mode, each one crafted to contain exactly the string my pattern looked for. All six passed. Then I pointed it at an actual...