What components or functions need to be checked during testing?

During testing, it is necessary to check the following components and functions:

• Functionality: whether the application's behavior meets the requirements and specifications.
• Usability: how convenient and understandable it is to use the application.
• Performance: response speed, load capacity, stability under a large number of users.
• Security: vulnerability testing, correctness of authorization and authentication.
• Compatibility: proper operation on different devices, browsers, and operating systems.
• Regression testing: to ensure that new changes do not break existing functionality.

It is also important to check error handling and the correctness of working with boundary values.