docs(rsc): add CONTRIBUTING.md (#613)

Co-authored-by: Claude <[email protected]>

Author: hi-ogawa

CONTRIBUTING.md

@@ -132,3 +132,7 @@ Some errors are masked and hidden away because of the layers of abstraction and
 In many test cases, we need to mock dependencies using `link:` and `file:` protocols. `pnpm` treats `link:` as symlinks and `file:` as hardlinks. To test dependencies as if they were copied into `node_modules`, use the `file:` protocol. Otherwise, use the `link:` protocol.
 
 For a mock dependency, make sure you add a `@vitejs/test-` prefix to the package name. This will avoid possible issues like false-positive alerts.
+
+## Contributing to `@vitejs/plugin-rsc`
+
+See [CONTRIBUTING.md](packages/plugin-rsc/CONTRIBUTING.md) in the `@vitejs/plugin-rsc` package for specific guidelines on contributing to the React Server Components plugin.

packages/plugin-rsc/CONTRIBUTING.md

@@ -0,0 +1,63 @@
+# Contributing to @vitejs/plugin-rsc
+
+This guide provides essential tips for contributors working on the RSC plugin.
+
+## Testing
+
+### E2E Test Setup
+
+Tests use Playwright and are located in `e2e/` and use `examples` as test apps.
+
+#### Test Fixture Patterns
+
+- `examples/basic` - comprehensive test suite for the RSC plugin
+- `examples/starter` - lightweight base template for writing more targeted tests using `setupInlineFixture` utility
+- `examples/e2e/temp/` - base directory for test projects
+
+### Adding New Test Cases
+
+**Expanding `examples/basic` (for comprehensive features)**
+Best for features that should be part of the main test suite. `examples/basic` is mainly used for e2e testing:
+
+1. Add your test case files to `examples/basic/src/routes/`
+2. Update the routing in `examples/basic/src/routes/root.tsx`
+3. Add corresponding tests in `e2e/basic.test.ts`
+
+**Using `setupInlineFixture` (for specific edge cases)**
+Best for testing specific edge cases or isolated features. See `e2e/ssr-thenable.test.ts` for the pattern.
+
+<!-- TODO: mention unit test -->
+
+## Development Workflow
+
+<!-- TODO: mention playwright vscode extension? -->
+
+```bash
+# Build packages
+pnpm dev # pnpm -C packages/plugin-rsc dev
+
+# Run examples
+pnpm -C packages/plugin-rsc/examples/basic dev # build / preview
+pnpm -C packages/plugin-rsc/examples/starter dev # build / preview
+
+# Run all e2e tests
+pnpm -C packages/plugin-rsc test-e2e
+
+# Run with UI (this allows filtering interactively)
+pnpm -C packages/plugin-rsc test-e2e --ui
+
+# Run specific test file
+pnpm -C packages/plugin-rsc test-e2e basic
+
+# Run with filter/grep
+pnpm -C packages/plugin-rsc test-e2e -g "hmr"
+
+# Test projects created with `setupInlineFixture` are locally runnable. For example:
+pnpm -C packages/plugin-rsc/examples/e2e/temp/react-compiler dev
+```
+
+## Tips
+
+- Prefer `setupInlineFixture` for new tests - it's more maintainable and faster
+- The `examples/basic` project contains comprehensive test scenarios
+- Dependencies for temp test projects are managed in `examples/e2e/package.json`