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Step-by-Step Guide Debugging Tests in Create React App

· 3 minutes de lecture
Ajay Dhangar

Debugging tests in a React application can be challenging, but fear not! We've got you covered with this step-by-step guide to help you overcome the common hurdles and make your tests shine. Let's dive in:

Step 1: Install Create React App​

If you haven't already set up your Create React App project, start by installing it:

npx create-react-app my-app
cd my-app

Step 2: Writing a Test​

Create a simple React component (e.g., a Button) in a separate file and write a test for it. For example:

src/Button.js
import React from 'react';

const Button = () => {
  return <button>Click Me</button>;
};

export default Button;
src/Button.test.js
import React from 'react';
import { render, screen } from '@testing-library/react';
import Button from './Button';

test('renders the button', () => {
  render(<Button />);
  const buttonElement = screen.getByText('Click Me');
  expect(buttonElement).toBeInTheDocument();
});

Step 3: Run the Tests​

Execute the tests using the following command:

npm test

Step 4: Spotting the Failure​

If the test fails, don't panic! First, identify the failing test case.

Step 5: Reproduce the Failure Locally​

Make sure the failure occurs consistently by reproducing it locally. Ensure that you're running the correct test files and dependencies.

Step 6: Debugging Techniques​

Now, let's employ some debugging techniques to resolve the issue:

6.1. Use console.log​

Place console.log statements at different points in your test to check the values of variables or components. For example:

test('renders the button', () => {
  render(<Button />);
  console.log(screen.getByRole('button').outerHTML);
  const buttonElement = screen.getByText('Click Me');
  console.log(buttonElement); // Check the button element in the console
  expect(buttonElement).toBeInTheDocument();
});

6.2. Utilize debugger​

You can use the debugger keyword to pause test execution at a specific point. Open your browser's developer tools to inspect variables and the call stack. For example:

test('renders the button', () => {
  render(<Button />);
  debugger; // Execution will pause here, and you can inspect the app and test code.
  const buttonElement = screen.getByText('Click Me');
  expect(buttonElement).toBeInTheDocument();
});

6.3. Inspect with Chrome DevTools​

Open your app in Chrome, right-click, and select "Inspect." Navigate to the "Console" tab to interactively debug your tests using the same tools you use for your regular app.

6.4. Snapshot Testing​

If you suspect issues with rendering, consider using snapshot testing. Jest can generate snapshots of your components and compare them for changes. Learn more about snapshot testing in the official documentation.

Step 7: Fix the Test​

Based on your observations during debugging, fix the failing test case. It might involve modifying the component or adjusting your expectations in the test.

Step 8: Rerun the Tests​

After making changes, run the tests again to ensure everything is working correctly:

npm test

Step 9: Celebrate Success!​

Congratulations! You've successfully debugged your test and conquered the Bug Monsters. Repeat these steps whenever you encounter testing issues in your React applications.