How to Fix Jest Error for Form Submission Test in React Login Component?

Описание к видео How to Fix Jest Error for Form Submission Test in React Login Component?

Learn how to resolve the Jest error: "Expected number of calls: = 1 Received number of calls: 0" in your React login component's form submission test.
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How to Fix Jest Error for Form Submission Test in React Login Component?

If you've encountered the Jest error - "Expected number of calls: >= 1 Received number of calls: 0" - while testing the form submission in your React login component, you're not alone. This error typically indicates that a function you expected to be called during the test, perhaps a submit handler or API call, wasn't invoked as anticipated.

Troubleshooting Steps

Verify Event Simulation: Ensure that your form submission event is correctly simulated in your test. If you're using Enzyme, the code should look something like this:

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

The simulate method mimics the form submission, and preventDefault is to stop the actual form submission in a testing environment.

Check for Correct Binding: Make sure the submit handler is properly bound to the form. In a functional component using hooks, it might look like this:

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

Ensure that your handleSubmit function is defined correctly and passed to the onsubmit attribute.

Mock Function: If you're using mock functions with Jest to test the function calls, confirm they are setup properly. Here's an example using jest:

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

Component Re-renders: Ensure that the state changes or re-renders in your component are handled properly. Ineffective state updates or missing dependencies in useEffect can sometimes prevent form submission.

Debugging: Insert console.log statements inside your submit handler and check whether they are executed during tests:

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

If you don't see the log, the form submission might not be properly triggered during the test.

Example Walkthrough

Below is a simplified illustration:

Login Component:

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

Jest Test:

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

Conclusion

By following these troubleshooting steps, you should be able to diagnose and resolve the Jest error related to form submission in your React login component. This will ensure your unit tests accurately reflect the component's expected behavior during form submissions.

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