Artificial Intelligence1 min read

Catching Bugs Before They Land: JiTTesting’s Human-on-the-Loop Approach at Full Scale

By · Published by Everything Blog

In short

The testing pipeline operates overnight using spare infrastructure capacity to evaluate code modifications flagged as risky by a historical model. It deploys parallel workflows—one targeting probable failure points using contextual diff summaries and another analyzing shifts through mutant-style testing—to uncover regressions that standard tools frequently overlook. To minimize false positives, an ensemble of models and traditional rules filters the results before escalating verified, high-risk issues to engineers.

Key points

  • Meta deployed this automated testing pipeline directly into production to safeguard hundr…: Meta deployed this automated testing pipeline directly into production to safeguard hundreds of millions of lines of code.
  • An ensemble of state-of-the-art models works alongside standard rules to filter out false…: An ensemble of state-of-the-art models works alongside standard rules to filter out false positives before human review.
  • Retaining human oversight for verified, high-risk alerts maintains labeling accuracy whil…: Retaining human oversight for verified, high-risk alerts maintains labeling accuracy while significantly lowering developer workloads.

Sources checked by our analysis pipeline: 1

- Over the last year we’ve been sharing our work leveraging large language models to catch bugs on the fly — a novel approach we call Catching Just-in-Time Tests (JiTTests).

- Now, we’re sharing the results and positive impact we’ve seen with Catching JiTTests deployed into production.

- Our paper, “Just-in-Time Catching Test Generation at Meta,” fully details our initial deployment and testing with Catching JiTTests.

Every code change improves our platform, but it also introduces new complexity. With hundreds of millions of lines of code constantly evolving at Meta, traditional testing can’t keep pace. Catching risks proactively, before code lands, enables us to identify risks earlier, respond more effectively, and deliver reliable experiences at scale.

Over the last year, we’ve shared our research into applying large language models (LLMs) to generate software tests. More specifically, we’ve shared our work with Just-in-Time Tests (JiTTests), a novel testing approach where we leverage LLMs to catch bugs on the fly, even ones that traditional testing might not catch.

In the five months since we first unveiled this work, we’ve deployed our Catching…

Artificial Intelligence