How to test custom Hooks in React ?

Custom Hooks in React are JavaScript functions that utilize built-in React hooks or other custom hooks to encapsulate reusable logic in functional components. They follow a naming convention where the function name starts with “use” (e.g., useCustomHook). Custom hooks allow users to abstract complex logic into reusable units, promoting code reusability and maintainability in React applications.

Testing custom hooks is similar to testing regular functions, and you can use testing libraries like Jest along with testing utilities for React like @testing-library/react-hooks

Steps to Test Custom Hooks:

Step 1: Install the necessary package in your application using the following command.

npm install --save-dev jest @testing-library/react-hooks

Step 2: Write a test file: For example, if you have a custom hook named useCustomHook in a file named customHook.js, you can create a corresponding test file like customHook.test.js.

Step 3: Write Test Cases: Import renderHook and act from @testing-library/react-hooks. Use renderHook to render the custom hook in a testing environment. Write test cases to assert the correctness of values and handle changes.

import { renderHook } from '@testing-library/react-hooks';
import useCustomHook from './useCustomHook';

Step 4: Run Tests: Execute tests using your preferred test runner, usually Jest.

npm test

Adjust tests based on the specific behavior of your custom hook. The act function is used to trigger side effects like function calls within the hook.

Advantages:

• Ensures correct functionality and prevents unexpected behavior.
• Provides a safety net for refactoring and making changes.
• Acts as living documentation and provides clear examples.
• Guards against regressions and maintains existing functionality.
• Facilitates collaboration in team environments.
• Integrates with Continuous Integration (CI) for automated testing.