Enhancing React Component Testing with JEST Helpers
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Chapter 1: Introduction to JEST Helpers
In this segment of our React and JEST journey, we’ll explore how to integrate helpful utilities into your project, making your testing experience more manageable. These tools extend the existing testing functionalities and streamline your workflow. If you’re feeling out of the loop or wish to revisit earlier discussions, don’t forget to check out parts 1 and 2 for additional insights.
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Creating a Testing Utility Wrapper
Reflecting on our initial chapter discussing the architecture of tests, you might remember a line like import { render, cleanup } from "@testing-library/react";. This line imports essential functions (render and cleanup) from the React testing library, which are crucial for executing tests—particularly for rendering components and managing cleanup.
Typically, your application should have a consistent way to structure components, and you might be utilizing certain libraries (such as Redux, internationalization tools, history management, or theme providers). If that’s the case, it’s beneficial to extend the testing utilities to simplify component testing, saving you from repetitive code and cumbersome setups each time you run a test. If you've struggled with this in the past or found it overly complex, you’ll appreciate the solutions provided in part 4 of this series.
The optimal approach is to create a test-utils wrapper around the @testing-library/react functionalities. Below is a demonstration of such a wrapper:
// Example of a testing utility wrapper
This example encompasses various features, including a theme provider, internationalization, Redux state management, and connected history through the connected-router package. Feel free to remove any elements you don’t use, or add your custom configurations as needed.
A few notes regarding the code:
- It includes a useRealStore flag, which will be accessible to the render method, allowing you to choose between the actual Redux store and a mocked version during tests. Generally, you won’t need the real store, as the focus should be on testing your own code.
- It exports all methods from the original @testing-library/react, enhancing the render method to be more intelligent and customizable, as it defines customRender with the custom wrapper and options.
Mocking the Store & State
Here is an example of mockStore.js set up with redux-saga. You can adjust this based on your configuration, as ample documentation is available for specific libraries.
This is a simplified, recommended setup for a redux-saga project that uses a preloaded state while registering all event listeners as defined in the project:
// Example of mockStore.js
Mocking the Internationalization Library
If your project uses multiple languages through i18next, you typically do not want to test external libraries, assuming they function correctly. Instead, you can mock the library with a default configuration and a single language of your choice. Below is a basic example using English as the default language, adhering to the library’s official guidelines:
// Example of i18TestConfig.js
Chapter 2: Practical Applications of JEST Helpers
The first video, "UI Testing with React, Mirage, Jest and Testing Library," provides practical insights into setting up UI testing for React applications.
The second video, "React Testing Course for Beginners – Code and Test 3 Apps," is designed for beginners and walks through coding and testing three applications.
Other parts in this series
- Part 1 (Getting Started + Useful Resources)
- Part 2 (Project Configuration)
- Part 4 (Testing Patterns)