Скачать или смотреть Solving the JestJS Issue with Multiple WebSocket Connections

Learn how to resolve the `JestJS` hanging issue when testing multiple WebSocket connections in JavaScript. This guide provides a clear solution with code examples.
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This video is based on the question https://stackoverflow.com/q/69906921/ asked by the user 'Joy Singh' ( https://stackoverflow.com/u/9578155/ ) and on the answer https://stackoverflow.com/a/69907718/ provided by the user 'erwinv' ( https://stackoverflow.com/u/2075151/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting JestJS: Multiple WebSocket Connections Hanging Issue

If you are a JavaScript developer, you might have encountered issues while testing WebSocket connections in your applications using JestJS. Specifically, you may have run into a situation where your Jest tests hang or don't complete when executing functions that create multiple WebSocket connections. This issue can be frustrating, as it may seem to work perfectly in the browser. In this guide, we'll explore the causes of this problem and provide a detailed solution to ensure you can run your tests smoothly.

Understanding the Problem

The core of the problem arises when Jest is used to test functionality that relies on WebSockets, particularly when multiple connections are involved. In your specific case, the code snippet you've provided attempts to create several WebSocket connections to a server to check when a game starts. Unfortunately, during testing in Jest, it hangs indefinitely, leading to uncertainty about the test results.

Example Code Causing the Issue

Here is the original function you had for checking the game start:

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Your test code snippet was as follows:

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The Solution

To address the hanging issue in Jest, you're going to need to refactor your code. The key to solving this is setting up a proper WebSocket server within your test environment and ensuring that Jest runs in the jsdom environment rather than the default Node environment.

Step 1: Set Up a WebSocket Server

You can utilize the ws NPM package to create a WebSocket server. Here is how to integrate it into your Jest setup:

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Step 2: Refactor the Main Function

Next, modify your checkGameStart function to handle multiple connections more elegantly using Promise.all. Here’s the updated function:

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Step 3: Update Your Jest Test Case

Make sure your test case is marked as async to accommodate the new changes:

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Step 4: Configure Jest to Use jsdom

Finally, you must ensure that your Jest environment is set to jsdom. Add this configuration to your jest.config.js file:

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Conclusion

By following the steps outlined above, you will successfully resolve the hanging issue when running Jest tests for multiple WebSocket connections. This not only ensures your tests are reliable, but also reflects the true functionality of your application as it would run in a web browser.

Now you can run your tests smoothly! Here is the expected output when you execute your test cases:

[[See Video to Reveal this Text or Code Snippet]]

With these enhancements, you can rest assured that your WebSocket connections are being tested accurately in Jest. Happy coding!