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Detox Design Principles

Traditionally, end-to-end tests on mobile are riddled with inherent issues, making the testing process difficult and lowering ROI for developers. We believe that the only way to solve these issues at the core is by changing some of the basic principles of our approach.


  • Detox does not rely on WebDriver

    Detox is built from the ground up to integrate with native layers of your mobile app directly. We try to avoid generic cross-platform interfaces that are often the lowest common denominator. We want to optimize per platform.

  • Detox does gray box, not black box

    Theoretically, it sounds better to test exactly what you ship as a black box. In practice, switching to gray box allows the test framework to monitor the app from the inside and delivers critical wins like fighting flakiness at the core.

  • Detox relies on EarlGrey and Espresso

    The leading native gray box drivers are developed by Google - EarlGrey for iOS and Espresso for Android. Detox relies on them using a JSON-based reflection mechanism which allows a common JavaScript implementation to invoke their native methods directly.

  • Friendly Protractor-like API for tests

    Tests in Detox are implemented in human-readable JavaScript and can even be shared between platforms. This easy to use API completely abstracts the complex native driver invocations taking place under the hood.

  • Detox controls devices through low-level APIs

    Let's take iOS simulators for example, which are difficult to control efficiently since multiple concurrent instances aren't supported. Detox uses AppleSimulatorUtils (another opensource library by Wix) to work around these issues and support test sharding.

  • Built from the ground up for mobile and React Native

    Detox is inspired by web testing methodologies but is not a direct translation of a solution designed for a different platform. Detox is built from the ground up for native mobile and has deep first-class support for React Native apps.

  • Detox relies on websockets for communication

    Communication between the test script running on Node.js and the tested app running on device uses websockets. This provides true bi-directional communication and is much faster and resilient than REST-like protocols.

  • Both tester and testee are websocket clients

    The test script running on Node.js and the tested app running on device are both clients. This allows one side to disconnect without affecting the other. A separate proxy websocket server is used to connect them.

  • Expectations run on the testee, not the tester

    Traditionally, test frameworks evalutate expectations in the test script running on Node.js. Detox evaluates expectations natively directly in the tested app running on device. This enables operations that were impossible before due to performance reasons.