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Testing Default Parameter Component Rendering in Create React App

This test suite validates the implementation of default parameters in React components within Create React App. It focuses on ensuring components using default parameter syntax render correctly and maintain expected behavior in a React environment.

Test Coverage Overview

The test suite provides fundamental coverage for React components utilizing default parameters. It verifies:

Basic component rendering functionality
Async rendering behavior with Promise resolution
Component mounting with default parameter props
Integration with ReactDOM rendering cycle

Implementation Analysis

The testing approach employs Jest’s describe/it pattern combined with React’s rendering lifecycle. It implements asynchronous testing patterns using Promises, ensuring component mounting completes before test completion.

The implementation leverages ReactDOM.render() with a callback pattern to verify successful component initialization.

Technical Details

Testing Framework: Jest
React Testing Dependencies: ReactDOM
Test Environment: jsdom
Component Testing Pattern: Async mounting verification
Setup Requirements: DOM element creation

Best Practices Demonstrated

The test suite exemplifies clean testing practices by isolating component rendering tests and handling asynchronous operations properly. It demonstrates:

Proper cleanup with isolated DOM elements
Async testing patterns with Promises
Component lifecycle handling
Minimal test case isolation

facebook/create-react-app

packages/react-scripts/fixtures/kitchensink/template/src/features/syntax/DefaultParameters.test.js

            
/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import React from 'react';
import ReactDOM from 'react-dom';
import DefaultParameters from './DefaultParameters';

describe('default parameters', () => {
  it('renders without crashing', () => {
    const div = document.createElement('div');
    return new Promise(resolve => {
      ReactDOM.render(<DefaultParameters onReady={resolve} />, div);
    });
  });
});