When extracting a reusable component during refactoring, which step is crucial?

Thoroughly testing to ensure existing functionality isn't broken after moving the component is vital during the process of extracting a reusable component. This step is fundamental because it helps verify that the refactoring has not inadvertently introduced bugs or issues in the application. When a component is extracted from its original module, there may be dependencies, interactions, or assumptions that can be disrupted. Comprehensive testing allows the development team to confirm that both the new reusable component and the original module continue to work as expected.

Ensuring that existing functionality remains intact involves validating both unit tests for the extracted component and integration testing for how it interacts with other parts of the system after the refactoring. This approach reinforces the stability of the application and preserves user experience, making it a crucial step in the refactoring process.