How to Stabilize React's useId Testing with Global Mocking

In React components, the need for unique identifiers is common. However, testing components that utilize the React.useId hook can be challenging due to the generation of a unique identifier for each test. While this uniqueness is valid, it can lead to varying snapshots in each test run, causing instability in snapshot tests.

To address this challenge and ensure stable tests, it is beneficial to mock the React.useId API globally. By doing so, you can consistently return the same value for the hook across all tests.

The Solution

While it is possible to mock React.useId on a per-test-file basis, this approach can be counterproductive and time-consuming. The optimal solution is to mock it globally, and this can be achieved within the jest.setup.ts file. In this file, you can mock any API, including React.useId, ensuring a uniform testing environment.

Here's an example of how to globally mock React.useId:

// jest.setup.ts 

// We're using all APIs from React.
// Only the useId hook is mocked. 
jest.mock("react", () => ({
  useId: () => "r:id",

By employing this setup, all your tests will consistently produce the same result, eliminating false negatives in your test scenarios. This approach is particularly recommended for projects with extensive React testing, providing a streamlined and stable testing experience. Consider incorporating this setup into your React projects to enhance the reliability and efficiency of your testing suite.