feat: Native iOS code coverage support

.nx/version-plans/add-experimental-ios-native-coverage.md

@@ -0,0 +1,5 @@
+---
+__default__: minor
+---
+
+Harness now offers experimental native iOS coverage for selected CocoaPods, so you can see which native code paths your Harness tests exercise. After a covered run, Harness produces `native-coverage.lcov`, giving you a concrete way to inspect and report native coverage alongside your existing test results.

packages/config/src/types.ts

@@ -104,6 +104,23 @@ export const ConfigSchema = z
               'Use ".." for create-react-native-library projects where tests run from example/ ' +
               "but source files are in parent directory. Passed to babel-plugin-istanbul's cwd option."
           ),
+        native: z
+          .object({
+            ios: z
+              .object({
+                pods: z
+                  .array(z.string())
+                  .min(1, 'At least one pod name is required')
+                  .describe(
+                    'Pod names to instrument for native code coverage. ' +
+                    'Coverage flags are injected at pod install time via a CocoaPods hook. ' +
+                    'After tests, profraw data is collected and converted to lcov format.'
+                  ),
+              })
+              .optional(),
+          })
+          .optional()
+          .describe('Native code coverage configuration.'),
       })
       .optional(),
 

packages/coverage-ios/HarnessCoverage.podspec

@@ -0,0 +1,27 @@
+require "json"
+
+package = JSON.parse(File.read(File.join(__dir__, "package.json")))
+
+if defined?(Pod::Installer)
+  require_relative 'scripts/harness_coverage_hook'
+end
+
+Pod::Spec.new do |s|
+  s.name         = "HarnessCoverage"
+  s.version      = package["version"]
+  s.summary      = package["description"]
+  s.homepage     = package["homepage"]
+  s.license      = package["license"]
+  s.authors      = package["author"]
+
+  s.platforms    = { :ios => "13.0" }
+  s.source       = { :git => "https://github.com/callstackincubator/react-native-harness.git", :tag => "#{s.version}" }
+
+  s.source_files = "ios/**/*.{h,m,mm,swift}"
+
+  if defined?(install_modules_dependencies)
+    install_modules_dependencies(s)
+  else
+    s.dependency "React-Core"
+  end
+end

packages/coverage-ios/README.md

@@ -0,0 +1,103 @@
+![harness-banner](https://react-native-harness.dev/harness-banner.jpg)
+
+### Experimental iOS Native Coverage for React Native Harness
+
+[![mit licence][license-badge]][license]
+[![npm downloads][npm-downloads-badge]][npm-downloads]
+[![Chat][chat-badge]][chat]
+[![PRs Welcome][prs-welcome-badge]][prs-welcome]
+
+⚠️ **EXPERIMENTAL** ⚠️
+
+`@react-native-harness/coverage-ios` adds native iOS code coverage collection for React Native Harness. It instruments selected CocoaPods, collects LLVM `.profraw` files from the app during test runs, and writes a `native-coverage.lcov` report after the run finishes.
+
+At the moment, coverage collection is supported on **iOS simulators only**.
+
+## Installation
+
+```bash
+npm install --save-dev @react-native-harness/coverage-ios
+# or
+pnpm add -D @react-native-harness/coverage-ios
+# or
+yarn add -D @react-native-harness/coverage-ios
+```
+
+After installation, run your iOS pod install step and rebuild the app.
+
+## Usage
+
+Add the pods you want to instrument in `rn-harness.config.mjs`:
+
+```javascript
+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'],
+      },
+    },
+  },
+};
+```
+
+Run Harness with coverage enabled:
+
+```bash
+react-native-harness --coverage --harnessRunner ios
+```
+
+When coverage is collected successfully, Harness writes:
+
+- `native-coverage.profdata`
+- `native-coverage.lcov`
+
+to the project root.
+
+## How it works
+
+- Injects coverage compiler and linker flags into the selected CocoaPods during `pod install`
+- Links a small helper pod that periodically flushes LLVM profile data from the running app
+- Stops the app before disposal so the final profile data is written
+- Merges `.profraw` files and exports them as LCOV
+
+## Requirements
+
+- macOS with Xcode installed
+- iOS runner configured with `@react-native-harness/platform-apple`
+- CocoaPods-based iOS project
+- Debug build of the app
+- `xcrun llvm-profdata` and `xcrun llvm-cov` available in Xcode toolchain
+
+## Limitations
+
+- iOS only
+- iOS simulator only for now
+- Experimental and subject to change
+- Designed for pod-based native dependencies listed in `coverage.native.ios.pods`
+- Coverage collection currently writes reports to the project root
+
+## Made with ❤️ at Callstack
+
+`@react-native-harness/coverage-ios` is an open source project and will always remain free to use. If you think it's cool, please star it 🌟. [Callstack][callstack-readme-with-love] is a group of React and React Native geeks, contact us at [hello@callstack.com](mailto:hello@callstack.com) if you need any help with these or just want to say hi!
+
+Like the project? ⚛️ [Join the team](https://callstack.com/careers/?utm_campaign=Senior_RN&utm_source=github&utm_medium=readme) who does amazing stuff for clients and drives React Native Open Source! 🔥
+
+[callstack-readme-with-love]: https://callstack.com/?utm_source=github.com&utm_medium=referral&utm_campaign=react-native-harness&utm_term=readme-with-love
+[license-badge]: https://img.shields.io/npm/l/@react-native-harness/coverage-ios?style=for-the-badge
+[license]: https://github.com/callstackincubator/react-native-harness/blob/main/LICENSE
+[npm-downloads-badge]: https://img.shields.io/npm/dm/@react-native-harness/coverage-ios?style=for-the-badge
+[npm-downloads]: https://www.npmjs.com/package/@react-native-harness/coverage-ios
+[prs-welcome-badge]: https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=for-the-badge
+[prs-welcome]: ../../CONTRIBUTING.md
+[chat-badge]: https://img.shields.io/discord/426714625279524876.svg?style=for-the-badge
+[chat]: https://discord.gg/xgGt7KAjxv

packages/coverage-ios/ios/HarnessCoverageHelper.swift

@@ -0,0 +1,60 @@
+#if HARNESS_COVERAGE
+import Foundation
+import UIKit
+
+@_silgen_name("__llvm_profile_write_file")
+func __llvm_profile_write_file() -> Int32
+
+@_silgen_name("__llvm_profile_set_filename")
+func __llvm_profile_set_filename(_ filename: UnsafePointer<CChar>)
+
+@objc(HarnessCoverageHelper) public class HarnessCoverageHelper: NSObject {
+  private static let profrawDir = "/tmp/harness-coverage"
+  private static var isSetUp = false
+  private static var flushThread: Thread?
+
+  @objc public static func setup() {
+    guard !isSetUp else { return }
+    isSetUp = true
+
+    try? FileManager.default.createDirectory(atPath: profrawDir, withIntermediateDirectories: true)
+    let profrawPath = "\(profrawDir)/harness-\(ProcessInfo.processInfo.processIdentifier).profraw"
+    __llvm_profile_set_filename(profrawPath)
+
+    startFlushTimer()
+
+    NotificationCenter.default.addObserver(
+      forName: UIApplication.willTerminateNotification,
+      object: nil, queue: nil
+    ) { _ in
+      _ = __llvm_profile_write_file()
+    }
+
+    NotificationCenter.default.addObserver(
+      forName: UIApplication.didEnterBackgroundNotification,
+      object: nil, queue: nil
+    ) { _ in
+      _ = __llvm_profile_write_file()
+    }
+
+    signal(SIGTERM) { _ in
+      _ = __llvm_profile_write_file()
+      exit(0)
+    }
+  }
+
+  private static func startFlushTimer() {
+    let thread = Thread {
+      let timer = Timer(timeInterval: 1.0, repeats: true) { _ in
+        _ = __llvm_profile_write_file()
+      }
+      RunLoop.current.add(timer, forMode: .default)
+      RunLoop.current.run()
+    }
+    thread.name = "HarnessCoverageFlush"
+    thread.qualityOfService = .background
+    thread.start()
+    flushThread = thread
+  }
+}
+#endif

packages/coverage-ios/ios/HarnessCoverageSetup.m

@@ -0,0 +1,25 @@
+// ObjC boot hook — Swift has no +load equivalent, so this bridges to HarnessCoverageHelper.setup().
+#import <Foundation/Foundation.h>
+
+@interface HarnessCoverageSetup : NSObject
+@end
+
+@implementation HarnessCoverageSetup
+
++ (void)load {
+#if defined(HARNESS_COVERAGE)
+  dispatch_async(dispatch_get_main_queue(), ^{
+    Class helper = NSClassFromString(@"HarnessCoverageHelper");
+    if (helper) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wundeclared-selector"
+      [helper performSelector:@selector(setup)];
+#pragma clang diagnostic pop
+    } else {
+      NSLog(@"[HarnessCoverage] ERROR: HarnessCoverageHelper class not found");
+    }
+  });
+#endif
+}
+
+@end

packages/coverage-ios/package.json

@@ -0,0 +1,37 @@
+{
+  "name": "@react-native-harness/coverage-ios",
+  "description": "Native iOS code coverage support for React Native Harness.",
+  "version": "1.1.0",
+  "type": "module",
+  "exports": {
+    "./package.json": "./package.json",
+    ".": {
+      "development": "./src/index.ts",
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js",
+      "default": "./dist/index.js"
+    }
+  },
+  "files": [
+    "src",
+    "dist",
+    "ios",
+    "scripts",
+    "*.podspec",
+    "react-native.config.cjs",
+    "!**/__tests__",
+    "!**/__fixtures__",
+    "!**/__mocks__",
+    "!**/.*"
+  ],
+  "peerDependencies": {
+    "react-native": "*"
+  },
+  "dependencies": {
+    "tslib": "^2.3.0"
+  },
+  "devDependencies": {
+    "react-native": "*"
+  },
+  "license": "MIT"
+}

packages/coverage-ios/react-native.config.cjs

@@ -0,0 +1,10 @@
+module.exports = {
+  dependency: {
+    platforms: {
+      ios: {
+        configurations: ['debug'],
+      },
+      android: null,
+    },
+  },
+};