When facing failed tests, it is crucial to have an effective debugging strategy. Here we present several techniques and tools you can use to identify and solve issues in your tests.

Using debugger and screen.debug()

To start, you can use the debugger statement in your code to pause execution at that point and open the debugger in your development environment. Additionally, Testing Library's screen.debug() prints the current state of the DOM, allowing you to visually inspect which elements are present and their states.

Example:

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Selector Verification

One of the most common issues in failed tests is the use of incorrect or fragile selectors. Make sure you are using the most robust selectors possible, such as getByRole, getByLabelText, and getByText.

Example:

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Waiting for Asynchronous Elements

When testing components that interact with asynchronous operations like API calls, make sure to use waiting methods like waitFor and findBy to handle these operations properly.

Example with waitFor:

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Example with findByText:

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Mocking and Stubbing

Make sure your mocks and stubs are correctly configured and are not interfering with the expected behavior. You can debug their behaviors by printing results to the console.

Example:

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Browser Debugging Tools

Running your tests in a real browser or in a browser-compatible testing environment (like Jest with the --runInBand option) can provide additional tools such as the Element Inspector, JavaScript Console, and other browser debugging features.

Live Reload Configuration

Some tools and development environments allow live reload, which can be useful to quickly see changes and debug on the fly.

Complete Example of a Debugging Session

Here is a complete example of a debugging session using several techniques mentioned above.

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[Placeholder for explanatory image: Diagram illustrating the debugging steps, from error identification to correction using the mentioned techniques]

Conclusion

Debugging failed tests can be challenging, but with the right tools and techniques, you can efficiently identify and resolve issues. We have covered various strategies ranging from using screen.debug() and console.log to setting breakpoints and correctly utilizing mocks.

In the next and final chapter, we will discuss conclusions and next steps to continue improving your testing skills with DOM Testing Library.