Native Coverage

    React Native Harness provides experimental support for collecting native coverage during test runs.

    Experimental

    @react-native-harness/coverage-ios is an experimental feature. Expect rough edges and API changes while the integration matures.

    Today, native coverage support is available for iOS simulators only. Physical iOS devices are not supported yet. Android support is planned and this guide will expand as it lands.

    What you get

    • Coverage instrumentation for supported native dependencies
    • Automatic .profraw collection from the app sandbox
    • native-coverage.lcov output after the test run finishes
    • A way to measure native code exercised by Harness tests, alongside JavaScript coverage

    Installation

    Current package:

    npm
    yarn
    pnpm
    bun
    deno
    npm install --save-dev @react-native-harness/coverage-ios

    After installation:

    1. Run your iOS pod install step.
    2. Rebuild the app.

    Configuration

    Current iOS configuration:

    Add the pods you want to instrument in rn-harness.config.mjs:

    import { applePlatform, appleSimulator } from '@react-native-harness/platform-apple';

export default {
  runners: [
    applePlatform({
      name: 'ios',
      device: appleSimulator('iPhone 16 Pro', '18.0'),
      bundleId: 'com.example.app',
    }),
  ],
  coverage: {
    native: {
      ios: {
        pods: ['MyLibrary'],
      },
    },
  },
};

    The pods array should contain CocoaPods target names that you want Harness to instrument for coverage.

    Running tests

    Current iOS command:

    Run Harness with coverage enabled:

    react-native-harness --coverage --harnessRunner ios

    Harness will stop the app before cleanup, collect generated .profraw files, merge them with llvm-profdata, and export LCOV with llvm-cov.

    Output

    When native coverage is collected successfully, Harness writes these files to the project root:

    • native-coverage.profdata
    • native-coverage.lcov

    Requirements

    • macOS with Xcode installed
    • An iOS runner configured with @react-native-harness/platform-apple
    • A CocoaPods-based iOS app setup
    • iOS Simulator
    • Debug app build

    Limitations

    • iOS simulator support is available today; physical iOS devices and Android are not supported yet
    • Current implementation targets pod-based native code
    • The feature is experimental and may change without much notice
    • If LCOV source filtering fails for pod paths, Harness falls back to exporting broader coverage data

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