Setting Up JSDOM with Jest for Frontend Testing

Frontend JavaScript applications often rely on the browser's DOM API for rendering and user interaction. When writing tests, it's crucial to have an environment that simulates this DOM. This challenge will guide you through configuring Jest to use JSDOM, a popular JavaScript implementation of the DOM, allowing you to test your frontend code effectively without needing a full browser.

Problem Description

Your task is to configure a Jest testing environment to utilize JSDOM. This means that when your Jest tests run, they should have access to a simulated browser environment, including the document object and other DOM APIs. You will need to ensure that JSDOM is properly integrated with Jest's test runner.

Key requirements:

• Jest Configuration: Modify Jest's configuration to explicitly set the test environment to "jsdom".
• DOM Access: Verify that within your Jest tests, you can access and manipulate the document object provided by JSDOM.
• Basic DOM Manipulation: Write a simple test that demonstrates interacting with the DOM (e.g., creating an element, appending it, checking its properties).

Expected behavior:

When running Jest tests, the tests should pass, and you should be able to use standard DOM methods and properties within your test files.

Important edge cases:

• Ensure your Jest configuration is correctly placed (e.g., jest.config.js or package.json).
• Consider potential conflicts if other testing libraries are also configured.

Examples

Example 1: Verifying DOM Availability

• Input: A Jest test file (my-test.test.ts) with the following content:

  describe('DOM Environment', () => {
    it('should have access to the document object', () => {
      expect(document).toBeDefined();
      expect(typeof document.createElement).toBe('function');
    });
  });
  

• Output: The Jest test runner reports this test as passing.

• Explanation: This test simply checks if the global document object and its methods are available, confirming that JSDOM has been successfully initialized.

Example 2: Basic DOM Manipulation Test

• Input: A Jest test file (dom-manipulation.test.ts) with the following content:

  describe('DOM Manipulation', () => {
    it('should allow creating and appending a div element', () => {
      const newDiv = document.createElement('div');
      newDiv.id = 'test-div';
      newDiv.textContent = 'Hello JSDOM!';
  
      document.body.appendChild(newDiv);
  
      const foundDiv = document.getElementById('test-div');
      expect(foundDiv).toBeDefined();
      expect(foundDiv?.textContent).toBe('Hello JSDOM!');
    });
  });
  

• Output: The Jest test runner reports this test as passing.

• Explanation: This test creates a div element, sets its ID and text content, appends it to the document.body, and then verifies its existence and content, demonstrating successful DOM interaction.

Constraints

• Jest Version: You are expected to use Jest version 27 or later.
• TypeScript: The solution and configuration should be in TypeScript.
• Project Setup: Assume a basic Node.js project with npm or yarn and TypeScript installed.
• No Actual Browser: The solution must work solely within a Node.js environment using Jest and JSDOM, without requiring a physical browser or headless browser instance for these specific tests.

Notes

• You will need to install jest and @types/jest as development dependencies.
• The JSDOM environment is typically configured in your Jest configuration file (e.g., jest.config.js or jest.config.ts).
• You might need to install jsdom and its types if it's not already a transitive dependency of Jest. However, newer versions of Jest often bundle JSDOM.
• Think about how Jest discovers and loads its configuration.
• The goal is to make document globally available in your test files.