All posts
Customers · 7 min read
How Quanta doubled test coverage in thirty days
A five-person platform team, a legacy billing service and a month-long experiment: 41% to 86% coverage without a freeze.
Ines DuarteCustomer Engineer ·
Quanta’s billing service had grown for six years with “we’ll add tests later” as its motto. Later arrived when a rounding bug cost a week of reconciliations.
The plan
- Generate characterization tests for every public function
- Review in batches of ten, never more
- Fix real bugs as separate PRs
Kestrel produced 1,140 tests across 212 files. The team kept 1,036, rewrote 61 and deleted the rest. Along the way they found and fixed nine genuine bugs.
The tests it writes are better than half of mine. We stopped arguing about coverage and started shipping.
Thirty days later, coverage sat at 86% and the deploy pipeline had not slowed down at all.
