---
title: "Testing Native Modules Reliably With JavaScript"
description: "Learn how React Native Harness bridges the gap between mocking and E2E testing: real device tests, full native access, Jest-style simplicity."
url: https://www.callstack.com/events/testing-native-modules-reliably-with-javascript
updated: 2026-10-24T08:39:22.518Z
---

# Testing Native Modules Reliably With JavaScript

Learn how React Native Harness bridges the gap between mocking and E2E testing: real device tests, full native access, Jest-style simplicity.

_Talk · 11/14/2025 · London, United Kingdom · Recording: 13:58 · Category: Testing_

Organizer: React Native London

Speakers: Michał Pierzchala (Principal Engineer @ Callstack)

[Watch the recording](https://www.youtube.com/watch?v=Tv1f146SpjQ)

Testing native modules in React Native can be challenging; mocking often hides real-world behavior, while full E2E test requires extra boilerplate and heavy tools. In this talk, Michał will make you familiar with React Native Harness. It offers a new middle ground: running tests directly on the simulator or device with full access to native modules, all while keeping a familiar Jest-style workflow. All in your favorite JavaScript.