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# React Test Renderer
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React Test Renderer is a deprecated React renderer that provides an experimental API for creating pure JavaScript object representations of React component trees without requiring a DOM or native mobile environment. It enables snapshot testing by rendering React components to JavaScript objects that can be serialized and compared across test runs.
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**⚠️ DEPRECATION NOTICE**: This package is deprecated as of React 19 and will be removed in a future version. The React team recommends [@testing-library/react](https://testing-library.com/docs/react-testing-library/intro) for DOM-based testing and @testing-library/react-native for React Native testing.
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## Package Information
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- **Package Name**: react-test-renderer
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- **Package Type**: npm
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- **Language**: JavaScript/TypeScript (with Flow types)
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- **Installation**: `npm install react-test-renderer`
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- **Version**: 19.1.1
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- **Status**: DEPRECATED
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## Core Imports
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```javascript
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import { create, act } from 'react-test-renderer';
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```
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For CommonJS:
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```javascript
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const { create, act } = require('react-test-renderer');
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```
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## Basic Usage
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```javascript
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import React from 'react';
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import { create } from 'react-test-renderer';
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// Create a test renderer instance
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const component = create(<div>Hello World</div>);
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// Get JSON representation for snapshot testing
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const json = component.toJSON();
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console.log(json);
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// { type: 'div', props: {}, children: ['Hello World'] }
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// Access the root instance for traversal
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const root = component.root;
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const divElement = root.findByType('div');
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// Update with new element
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component.update(<div>Updated Content</div>);
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// Clean up
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component.unmount();
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```
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## Architecture
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React Test Renderer is built around several key components:
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- **Test Renderer Creation**: The `create()` function that instantiates a test renderer for a React element
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- **JSON Serialization**: Converting the rendered tree to plain JavaScript objects for snapshot testing
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- **Tree Traversal**: ReactTestInstance class providing methods to search and navigate the component tree
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- **Component Lifecycle**: Update and unmount capabilities for testing component behavior over time
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- **React Integration**: Built on React's reconciler for accurate representation of React's rendering behavior
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## Capabilities
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### Test Renderer Creation
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Core functionality for creating test renderer instances and managing their lifecycle. Essential for all testing scenarios.
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```javascript { .api }
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function create(
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  element: React.ReactElement<any>,
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  options?: TestRendererOptions
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): TestRenderer;
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interface TestRendererOptions {
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  createNodeMock?: (element: React.ReactElement<any>) => any;
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  unstable_isConcurrent?: boolean;
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  unstable_strictMode?: boolean;
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}
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interface TestRenderer {
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  toJSON(): ReactTestRendererNode | Array<ReactTestRendererNode> | null;
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  toTree(): any;
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  update(element: React.ReactElement<any>): void;
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  unmount(): void;
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  getInstance(): React.Component<any, any> | any | null;
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  readonly root: ReactTestInstance;
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  unstable_flushSync: (fn: () => void) => void;
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}
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```
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[Test Renderer Creation](./test-renderer.md)
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### Tree Traversal and Search
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ReactTestInstance methods for navigating and searching the rendered component tree. Critical for making assertions about rendered components.
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```javascript { .api }
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class ReactTestInstance {
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  readonly type: any;
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  readonly props: object;
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  readonly parent: ReactTestInstance | null;
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  readonly children: Array<ReactTestInstance | string>;
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  readonly instance: any;
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  find(predicate: (node: ReactTestInstance) => boolean): ReactTestInstance;
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  findByType(type: any): ReactTestInstance;
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  findByProps(props: object): ReactTestInstance;
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  findAll(predicate: (node: ReactTestInstance) => boolean, options?: FindOptions): Array<ReactTestInstance>;
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  findAllByType(type: any, options?: FindOptions): Array<ReactTestInstance>;
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  findAllByProps(props: object, options?: FindOptions): Array<ReactTestInstance>;
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}
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interface FindOptions {
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  deep?: boolean;
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}
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```
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[Tree Traversal](./tree-traversal.md)
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### Utilities
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Testing utilities for managing React updates and batching.
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```javascript { .api }
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function act(callback: () => void | Promise<void>): Promise<void>;
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function unstable_batchedUpdates<T>(callback: () => T): T;
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```
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## Types
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```javascript { .api }
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type ReactTestRendererNode = ReactTestRendererJSON | string;
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interface ReactTestRendererJSON {
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  type: string;
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  props: { [propName: string]: any };
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  children: Array<ReactTestRendererNode> | null;
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  $$typeof?: symbol;
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}
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type Predicate = (node: ReactTestInstance) => boolean | null;
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```
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## Constants
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```javascript { .api }
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const version: string;
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const _Scheduler: any;
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```
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## Removed Features
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### Shallow Renderer
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The shallow renderer (`react-test-renderer/shallow`) has been completely removed as of React 19. Attempting to import it will throw an error:
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```javascript
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// This will throw an error
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import shallow from 'react-test-renderer/shallow';
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// Error: "react-test-renderer/shallow has been removed. See https://react.dev/warnings/react-test-renderer."
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```
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## Common Errors
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- **"Can't access .root on unmounted test renderer"**: Thrown when accessing properties after unmounting
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- **"Can't read from currently-mounting component. This error is likely caused by a bug in React. Please file an issue."**: Thrown when accessing component during mount process  
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- **"No instances found" / "Expected 1 but found N instances"**: Thrown by find methods when results don't match expectations
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- **"react-test-renderer/shallow has been removed"**: Thrown when attempting to import the removed shallow renderer