I audited my tool, fixed 44 bugs - and it still didn’t work

252 green tests, zero traces in Jaeger, and the one-line OpenTelemetry mistake that made my observability tool blind. TL;DR I shipped an observability tool with 252 green tests — but zero traces ever reached Jaeger. The root cause was an OpenTelemetry config detail that looked harmless ( spanProcessors: [] ) but silently disabled trace export. Manual testing found it in minutes. Act 1 · Act 2 · Root cause · Fix · Checklist · Links I shipped v2.2.0 of my observability tool with 143 tests and a green CI run. Then I did what I thought was the responsible thing: a deep code + DX audit. I found 44 issues, fixed them in a sprint, bumped the version a bunch of times, and ended at v2.4.4 with 252 tests. I felt great — until I ran the tool like a real user would. Zero traces were reaching the backend. Not “sometimes.” Not “misconfigured.” Just: never. 252 unit tests. All green. Traces were broken since day one. This is how I found out, what the root cause was, and why tests (and code audits) di