Szymon Rybczak, Co-founder & CEO of TesterArmy, joins us in the studio at Agent Conf 2026 in Warsaw to discuss AI testing for web and mobile apps and his journey from Callstack to Y Combinator.
We talk about why manual QA struggled to keep pace with agent-written code, how TesterArmy creates test plans around pull requests, and the choices behind its managed platform and open-source tooling. Szymon also shares what it was like to build a company while finishing high school and why his first hire was a designer.
Building a company while finishing high school
Szymon describes founding TesterArmy during his final year of high school, studying for exams with friends on Discord while attending Y Combinator. His co-founder, Oskar Kwaśniewski, also previously worked at Callstack.
Their experience building open-source libraries and developer tools shaped the company. After trying consumer apps, they returned to an area they knew from their own work: the gap between shipping code and checking that it works.
AI startups, hardware, and robotics at YC
We ask whether everyone at Y Combinator is building with AI. Szymon shares his impressions of the batch and describes the hardware and robotics startups he encountered.
He discusses why investors are watching robotics for its own breakthrough moment. The conversation offers his perspective as a founder going through the accelerator alongside teams working on different parts of AI.
Testing web and mobile apps with agents
Szymon explains how manual QA became a bottleneck as teams used agents to write more code. He and Oskar wanted a testing tool developers could try themselves and evaluate before bringing it to their managers.
TesterArmy started with web testing because browsers were faster to set up and iterate on. Szymon describes its expansion to native and React Native apps on iOS simulators and Android emulators, with the same goal: checking changes whether a person or an agent wrote the code.
Test plans that follow the pull request
Teams can start with a website URL or an uploaded app binary, then provide business-specific knowledge so the agent can distinguish an intended behavior from a bug.
Szymon also explains how the platform uses a pull request's diff and description to create a test plan for that change. That gives teams a way to check a new feature alongside their existing tests and add those checks to their regular testing group.
A managed platform and open-source testing tools
We ask how much control users have over the underlying model. Szymon explains that TesterArmy manages model selection and infrastructure within its hosted product.
He also outlines his plans for e2e, an open-source TypeScript SDK for building tests with a team's own model credentials and infrastructure. He says the SDK will use agent-device under the hood for mobile testing. The conversation covers the different needs of teams that want a managed service and developers who want to build their own agents.
A designer as the first hire and better tools for QA
TesterArmy's first hire was a designer who created its pixel-art logo and animation. Szymon explains why brand and product quality deserved that investment, and how coding agents let the designer contribute to the codebase.
We also ask what agentic testing means for QA roles, and Szymon describes working with QA teams and building tools they can use in their work.
About the guest
Szymon Rybczak is Co-founder & CEO of TesterArmy, a Y Combinator-backed company building AI testing tools for web and mobile apps. He previously worked at Callstack on React Native infrastructure and open source, including react-native-ai.
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