How to test a dropdown selector with value in React using React Testing Library

Discover how to effectively test dropdown selectors in React with React Testing Library with simple, clear examples for better unit testing.
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Testing Dropdown Selectors in React with React Testing Library

Introduction

When working with forms in React, managing dropdown selectors can be one of the trickier elements to handle, especially when it comes to unit testing. One commonly faced issue is ensuring that the dropdown selector has the correct default value selected. This post will guide you through the process of testing a dropdown selector using React Testing Library. We will take a look at a sample dropdown created with react-hook-form and yup, and we'll address a common testing problem that developers encounter.

The Problem

Let's imagine you have a dropdown selector component that is supposed to allow users to select an available sensor from a list. Here's a snippet of the relevant code that might look familiar:

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

When you're writing a test case to ensure that selecting an option works correctly, you might encounter an error similar to:

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

This error indicates that the testing library cannot find the option value in the dropdown options. The reason behind this is that the select behavior is not being achieved in a standard way.

Solution Overview

To effectively test that a dropdown selector has a value set, you need to simulate user interactions properly. Below are the steps to accomplish this in a well-structured manner:

1. Simulating User Interaction

Since the dropdown uses a button to render its options, the first step is to simulate a click on the button to reveal the dropdown options. After clicking, you can select an option.

Code Example

Here's how to write a test to ensure the dropdown behavior works as expected:

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

2. Validating Value Change

In addition to verifying that the expected value appears after selection, it’s also a good practice to check that the initial state didn’t contain an unrelated option.

Code Example

You can run a test similar to this to assert the correct behavior:

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

3. Mocking Functions in Tests

If you also want to verify that the associated function (like postData) is called when the dropdown value is submitted, you can mock this function.

Code Example

Here's how you'd mock an intended function call in your test:

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

Conclusion

Testing dropdown selectors in React can be tricky due to the interactive nature of forms. However, by following the steps outlined here, you can effectively simulate user actions to ensure the dropdown behaves as intended. Remember to always interact with components as a user would, which includes showing options and selecting from them.

With this guide, you should be better equipped to handle dropdown selectors in your React applications with React Testing Library. Happy testing!