migrating-from-react-test-renderer.md

Migration from React Test Renderer

This library replaces the deprecated React Test Renderer. The main differences:

• Host element focus: Operates on host components by default, while React Test Renderer worked with a mix of host and composite components. Access the underlying fiber via unstable_fiber if needed.
• Built on React Reconciler: Uses React Reconciler to implement a custom renderer.
• Exposed reconciler options: Most React Reconciler configuration options are available through RootOptions.

For most use cases, the migration is straightforward:

// Before (React Test Renderer)
import TestRenderer from "react-test-renderer";
const tree = TestRenderer.create(<MyComponent />);

// After (Test Renderer)
import { createRoot } from "test-renderer";
const root = createRoot();
await act(async () => {
  root.render(<MyComponent />);
});
const tree = root.container;