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Writing End-to-End Tests for DOM Manipulation

In this tutorial, we'll teach you how to write end-to-end tests for DOM manipulation using Cypress, a popular testing framework.

Setting up Cypress​

To set up Cypress, follow these steps:

  1. Create a new project folder and navigate to it in your terminal.

  2. Initialize a new npm project with the following command:

npm init -y
  1. Install Cypress with the following command:
npm install --save-dev cypress
  1. Add a new cypress:open script to your package.json file:
"scripts": {
  "cypress:open": "cypress open"
}
  1. Run Cypress for the first time with the following command:
npm run cypress:open

This command will generate a cypress folder with example tests and configuration files.

Writing a simple DOM manipulation function with user interaction​

Create a new file called index.html in your project folder and add the following code:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>End-to-End Test</title>
  </head>
  <body>
    <button id="clickButton">Click me!</button>

    <script>
      const button = document.getElementById('clickButton');
      button.addEventListener('click', () => {
        button.textContent = 'Clicked!';
      });
    </script>
  </body>
</html>

This code creates a button element with a click event listener. When the button is clicked, its text content changes to "Clicked!".

Writing the end-to-end tests​

Create a new file called dom_manipulation_spec.js in the cypress/integration folder and add the following code:

describe('DOM Manipulation', () => {
  beforeEach(() => {
    cy.visit('index.html');
  });

  it('should change the button text when clicked', () => {
    cy.get('#clickButton').should('contain', 'Click me!').click().should('contain', 'Clicked!');
  });
});

In this test file, we set up a beforeEach function to load the index.html file. We then write a test case to find the button using its ID, check that it contains the correct initial text, click it, and verify that the button's text content changes as expected.

Running the tests​

To run the tests, execute the following command in your terminal:

npm run cypress:open

Cypress will open its test runner, and you can click the dom_manipulation_spec.js file to run the test.

By writing end-to-end tests for DOM manipulation using Cypress, you can ensure that your web applications behave as expected in real-world scenarios. This can help you identify and fix bugs more efficiently and maintain a high level of code quality throughout your project.