Heapspace Meetup #36 „Mutation Testing in the Age of AI-Generated Code“

Most teams track code coverage. Some even celebrate 100%. But coverage only tells you which lines were executed, not whether your tests would catch a real bug.
Mutation testing flips the perspective. Instead of measuring how much code runs, it intentionally introduces small faults into your code and checks whether your tests detect them. If they don’t, your test suite may be weaker than it looks.
In this talk, I’ll start with a short, practical introduction to mutation testing and why it matters. Then we’ll look at how to apply it in JavaScript and TypeScript projects using modern tooling. I’ll share real-world lessons from running mutation testing in production libraries — including performance challenges, CI strategies, and how to avoid turning it into an expensive vanity metric.
Finally, we’ll discuss why mutation testing becomes even more important in the era of AI-assisted development. When AI agents generate code and tests for us, how do we know they are actually robust? Mutation testing might be the missing feedback loop.

Speaker: Dmitrii Suroviagin, Lead Software Engineer at EPAM

Dmitrii is a Lead Software Engineer at EPAM Systems with over five years of experience building and modernizing large-scale web platforms. He specializes in transforming legacy systems into scalable applications using React, Next.js, and TypeScript on cloud infrastructure such as AWS and Azure. Dmitrii is an AWS AI Practitioner and Azure DevOps Engineer Expert, maintains open-source projects focused on code quality, and enjoys hiking in the Serbian mountains when he’s not writing code.