What is the purpose of visual regression libraries?

Visual regression libraries are designed specifically to assist developers and testers in the implementation of visual testing. Their primary purpose is to facilitate the process of comparing visual representations of applications over time to ensure that any changes in the code do not inadvertently alter the user interface or visual components in unintended ways. By automating the comparison of screenshots or rendered pages, these libraries help identify visual discrepancies that might arise due to updates or code changes, enhancing the overall effectiveness and reliability of visual testing practices.

The other options do not align with the core function of visual regression libraries. Enhancements to backend testing capabilities, monitoring server performance, or managing database transactions are unrelated to visual testing and focus on different aspects of software development and quality assurance. Therefore, the choice that points to the tools and methods for implementing visual testing directly captures the essential role of visual regression libraries in maintaining the visual integrity of applications.