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Struggling to mock Axios in your React and TypeScript tests? Discover effective strategies to solve it with clarity.
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How to Mock Axios Create in Your React and TypeScript Tests

Mocking API calls in unit tests can often be challenging, especially when employing libraries like Axios in a React and TypeScript environment. If you're finding it difficult to effectively mock an Axios instance in your tests, you’re not alone. This guide will guide you through the process of mocking Axios in a way that keeps your tests focused, organized, and functioning as intended.

Understanding the Problem

You might be writing a React application that uses Axios for API calls, and you want to write unit tests to ensure that your functions behave correctly. For example, you might be testing a function that deletes an item from a list when a user clicks a delete button. Your particular situation involves using an Axios instance and encountering errors when trying to mock it in your tests.

Common Scenario:

You created an Axios instance in a separate file and used it in your API functions.

Testing the delete functionality resulted in errors such as "Cannot read property 'data' of undefined."

This typically occurs when Axios isn't properly mocked, leading to confusion between the module you intend to test and the default configuration.

Step-by-Step Solution

1. Create a Separate Axios Instance

For testing purposes, it’s beneficial to encapsulate your Axios instance in its own module. This allows you to mock it separately during your tests.

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

2. Mock the Axios Instance in Your Test

In your test file, use Jest's mocking features to ensure that the Axios instance is correctly stubbed.

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

3. Test Behavior

In the above example, we:

Mocked the delete method of the Axios instance so that it returns a resolved promise.

Checked if the delete function was called with the right parameter after clicking the delete button.

Summary

Mocking Axios can seem daunting when managing multiple instances and configurations. However, leveraging a separate Axios instance module and mocking it correctly in your tests can simplify the process significantly.

Conclusion

While this guide focuses on mocking the delete function in an Axios instance, the principles can be applied to other HTTP verbs as well. So, if you’ve previously struggled with similar tests, try this structured approach for effective and efficient results.

If you have any other strategies or tips to share regarding Axios testing in React and TypeScript, feel free to contribute in the comments!