How to Test React Context? React Testing Context

Are you someone who is just beginning to start your career in this field and is trying to figure out how to start? Are you unable to find the error in your code and are stuck at a single problem for hours? This is the right place for all your queries.

This article will provide a complete 101 guide in the react testing context. One of the most essential steps in the development process is testing your React apps.

In this article, we will go through all the steps for testing the react context, from setting up the project to performing react testing context. To help you feel more confident in the dependability of your context and the components that depend on it, we’ll go through various testing methods and resources, such as the React Testing Library and Jest.

Your ability to build reliable and error-free apps will increase if you know how to test React Context, regardless of your experience level with React. Now, let’s get started and see how to use testing to its full potential within the React framework.

What is React Context?

To put it briefly, React Context is a feature that lets components communicate data without explicitly requiring props forwarding. Its three components—a provider, a consumer, and a context object.

It makes it simpler to communicate and maintain state throughout your application. Mainly when working with globally distributed data requirements or highly nested components.

Visit: What is React Context?

Why and when do we use it?

React is primarily utilized in single-page apps, content management systems, e-commerce platforms, progressive online apps, and mobile applications that employ React Native to create dynamic, interactive user interfaces for the web and mobile.

It’s excellent at handling complicated states and building reusable user interface components.

Setting up the project/ Environment

We can make a new project in the react testing context by following the below-given steps:

create-react-app test-prj

cd test-prj

We’ll be using the Jest and React Testing Library as our testing tools.

Jest

Facebook created the well-known testing library Jest. Its straightforward APIs make testing a breeze.

React Testing Library

We can test React components with the React Testing Library, a testing framework built on top of the DOM Testing Library. If the tool is not already installed, you can install it by running npm install –save-dev @testing-library/react.

Use the following command to install Jest: npm install –save-dev jest.

Tests are written in js/ts files, but before the.js/ts, we put.test so that Jest and the React Testing Library can recognize them. This is the only way to identify our test files to the testing libraries in the react testing context. Add.test.js will be the name of our test file for the add method.

Writing a Component Using Context

Let’s develop a basic context and a component that depends on it to show how to test React Context. We will build a component that shows the user’s name and a context for user authentication.

// UserContext.js

import React, { createContext, useContext } from ‘react’;

const UserContext = createContext();

export function useUser() {

  return useContext(UserContext);

}

export function UserProvider({ children }) {

  const user = { name: ‘John’ };

  return (

    <UserContext.Provider value={user}>

      {children}

    </UserContext.Provider>

  );

} 

We will now build a component that makes use of this context’s useUser hook.

// UserComponent.js

import React from ‘react’;

import { useUser } from ‘./UserContext’;

function UserComponent() {

  const user = useUser();

  return (

    <div>

      <h1>Hello, {user.name}!</h1>

    </div>

  );

}

export default UserComponent;

Testing the Component with Mocked Context

We can begin testing now that we have our components and context. We must mock the UserContext to supply arbitrary data for testing to test the UserComponent. Here’s a simple test that uses Jest and the React Testing Library:

// UserComponent.test.js

import React from ‘react’;

import { render } from ‘@testing-library/react’;

import UserComponent from ‘./UserComponent’;

import { UserProvider } from ‘./UserContext’;

test(‘renders user name’, () => {

  const { getByText } = render(

    <UserProvider>

      <UserComponent />

    </UserProvider>

  );

  const userName = getByText(‘Hello, John!’);

  expect(userName).toBeInTheDocument();

});

This test ensures the context is present when rendering UserComponent wrapped in UserProvider. We then locate the string “Hello, John!” using getByText and declare its presence in the DOM.

See Also: Best Books To Learn React: Top Recommendations For Aspiring Developers

Testing Context Provider

The Context Provider has to be tested first. And most coders get stuck at this point. With Context Consumer, it is easier to try Context Provider. However, there is a relatively straightforward fix for this issue. All we have to do is put into practice a test component that our unit tests will need.

There are just two items we need to evaluate in the testing phase:

1. Is the default theme appropriately set?
2. Can the theme be changed?

Now that we have this knowledge, let’s put the unit tests into practice. More than testing a single component is required. You must also test the provider to ensure that UserProvider provides the right context values. Here’s how to accomplish it:

// UserContext.test.js

import React from ‘react’;

import { render } from ‘@testing-library/react’;

import { UserProvider, useUser } from ‘./UserContext’;

test(‘provides the user context’, () => {

  const { result } = renderHook(() => useUser(), {

    wrapper: UserProvider,

  });

  expect(result.current.name).toBe(‘John’);

});

The renderHook method from @testing-library/react-hooks is used in this test to evaluate the context provider. It enables us to test the useUser hook in the UserProvider context that the UserContext supplies.

See Also: Link Image In React: Displaying Visual Content In React Components

Advanced Testing Scenarios

You may need to test component behavior under various context values or when context modifications in more complicated circumstances trigger component re-renders.

You can simulate context shifts using Jest’s mocking features. Mocking the context allows you to test different scenarios and get different values back.

To give distinct values for various test cases in the react testing context, you may substitute the actual implementation of useContext in your context module with jest. mock.

You can test how your components respond to various updates and context states. Here are some examples of advanced testing scenarios for React Context:

Dynamic Context Changes

Test the behavior of components when dynamic context changes change the context values. You can test how the component reacts to changes in context, such as when a user checks in or logs out.

See Also: UseContext Is Not Updating State: How To Fix?

Nested Context Providers

Some apps may have more than one nested context provider. Examine the interactions that components have with varying tiers of context providers.

Error Handling

Test your components’ error handling mechanisms for handling errors within context providers. For instance, how does your component react if an API request inside a context provider fails? To guarantee that your components handle fault circumstances gracefully, use Jest’s mocking feature.

See Also: Render HTML Strings With React: Boost Your Web Development

FAQs

What is the significance of testing React Context?

To ensure your application's shared state functions as intended, you must test React Context. It ensures that context-consuming components react effectively to changes in context values, helps identify defects early in the process, and verifies that context providers function correctly.

How can I test components that rely on multiple nested context providers?

You may set up a testing environment that mimics the nested context hierarchy to test components that rely on nested context providers. Ensure each level has the appropriate context values, and utilize Jest's mocking features to mimic the intended context conditions.

What's the role of Jest's mocking in testing React Context?

The mocking features of Jest come in handy for testing React Context. Mocks can be used to substitute controlled values for actual context implementations. This enables you to thoroughly test the behavior of your components under multiple contexts by simulating context updates, error scenarios, and changing context conditions.

Conclusion

Creating reliable React apps requires React Testing Context. You may save time and effort by identifying problems early in development with an adequately tested environment and components. This article addresses the fundamentals of testing React Context with Jest and the React Testing Library.

See Also: OnBlur Vs OnChange In React: Event Handling In Modern Web Apps