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30:27

10/4/2025

12:30PM - 1PM [CET]

Online

Write Once, Test Everywhere: Cross-Platform Testing for React Native

Date

Saturday, October 4, 2025

Time

12:30PM - 1PM [CET]

Location

Alicante

Online

Write Once, Test Everywhere: Cross-Platform Testing for React Native

Cross-platform testing in React Native made simple: a lightweight architecture to run and extend tests on any JavaScript-powered platform.

Date

04 October 2025

-

Time

12:30PM - 1PM [CET]

Location

Alicante

Online

Write Once, Test Everywhere: Cross-Platform Testing for React Native

Organizer

Organizer

Presented

React Alicante

@

Speakers

Speakers

Featuring

Łukasz Chludziński

Engineering Manager

@

Callstack

Featuring

Łukasz Chludziński

Engineering Manager

@

Callstack

Testing React Native apps has always meant choosing between speed and realism. Jest is fast, familiar, and great for unit tests; but it runs in Node.js with mocks for native modules. End-to-end frameworks give you realism, but at the cost of setup, maintenance, and slow pipelines.

At React Alicante 2025, Łukasz Chludziński introduces React Native Harness, a new testing framework created by Szymon Chmal at Callstack. Harness runs Jest-style tests directly on real devices and simulators, with full access to native modules and no mocks by default.

You'll see:

How Harness plugs into Metro to run tests inside the real runtime
Testing native libraries like MMKV without custom runners or hacks
Verifying spec compliance for APIs like fetch and WebSocket
How developers can keep their familiar Jest DX while gaining native access
Why this fills the "missing middle ground" between unit tests and E2E

Need QA that keeps up with AI-native delivery?

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Write Once, Test Everywhere: Cross-Platform Testing for React Native

Cross-platform testing in React Native made simple: a lightweight architecture to run and extend tests on any JavaScript-powered platform.

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