TDD Isn't Enough: How Benchmarks Turned Green Tests Into Real Evidence

Fri, 22 May 2026 00:00:00 +0000

There’s a moment in TDD that every developer has hit: all the tests are green, coverage is at 90-something percent, and you’re still not confident the code is actually correct. Either the tests are testing the wrong things, or they’re testing the right things but missing a whole class of bugs that coverage metrics can’t see.

I hit that moment twice on the same feature while building SIRA, a FastAPI-based invoice reminder system. What pulled me out of it wasn’t more tests — it was a different kind of test.

Tdd on ppl-blog

TDD Isn't Enough: How Benchmarks Turned Green Tests Into Real Evidence