https://getfelix.dev/topics/testing/ Felix blog posts about testing. en https://getfelix.dev/blog/felix-0-5-to-0-6.html https://getfelix.dev/blog/felix-0-5-to-0-6.html Sat, 24 Oct 2026 00:00:00 +0000 What we found, fixed and added between Felix 0.5.0 and 0.6.0: the bugs that shared one shape, the ways we found them, the features that apps asked for and why, and what building it taught us. https://getfelix.dev/blog/before-you-loosen-the-timeout.html https://getfelix.dev/blog/before-you-loosen-the-timeout.html Sat, 17 Oct 2026 00:00:00 +0000 Intermittent failures in Felix's cluster tests kept turning out to be real bugs in the broker, so before loosening a timeout I now run the test against a commit from before the suspect change; three cases show what that finds. https://getfelix.dev/blog/acknowledged-then-forgotten.html https://getfelix.dev/blog/acknowledged-then-forgotten.html Sat, 17 Oct 2026 00:00:00 +0000 Under Felix's default periodic fsync, a crashed broker could come back missing records it had acknowledged while the cluster still counted it as caught up; this is how review and the TLA+ model found it on the follower and leader sides, and what the fix costs. https://getfelix.dev/blog/catching-a-one-percent-regression.html https://getfelix.dev/blog/catching-a-one-percent-regression.html Sat, 17 Oct 2026 00:00:00 +0000 Felix's rule is that a release must not be measurably slower than the one before it; this is how same-runner A/B runs, a Welch's t-test and throwaway bisect PRs in GitHub Actions find a 1-2% loss, and why a single benchmark run can't. https://getfelix.dev/blog/checking-nothing.html https://getfelix.dev/blog/checking-nothing.html Fri, 16 Oct 2026 00:00:00 +0000 Felix checks 107 TLA+ configurations in CI; this is about three times a passing check meant nothing, and the twin configurations, reachability checks and spec pairing we use to catch it.