feat: add Harness plugin hooks

[V3RON]

What changed

Harness now has a first-class plugin system. Users can register Harness plugins in rn-harness.config.*, and those plugins can tap into key lifecycle and runtime events during a test run.

Why this was added

Plugins give us a stable extension point for features that should live outside core Harness. Instead of adding plugin-specific config fields or platform APIs directly to Harness, we can build those features as plugins.

What Harness plugins are

Harness plugins are user-configured extensions loaded from the Harness config file. A plugin can observe or react to events such as Harness startup, Metro activity, app lifecycle signals, collection, and test execution, and run custom Node.js logic around them.

What this enables

This is the foundation for custom integrations such as native coverage collection, reporting, or other workflow-specific extensions, while keeping the core Harness API smaller and cleaner.

Also included

• a new @react-native-harness/plugins package built on hookable
• plugin event emission wired into the Jest/Harness runtime
• a simple playground plugin that logs each plugin event so the system is easy to verify

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Project	Deployment	Actions	Updated (UTC)
react-native-harness	Ready	Preview, Comment	Mar 30, 2026 9:34am