Is it possible to perform regression testing of the authorization system using the same user?

Yes, regression testing of the authorization system can be conducted using the same user, but with some caveats:

• This approach is convenient for checking the repeatability and stability of functionality for a specific user.
• It is important that the user's state is predictable and controllable (e.g., password, access rights, account status).
• If tests change the user's state (e.g., block the account, change the password), it is necessary to ensure the restoration of the state between tests.
• For more comprehensive coverage, it is advisable to use different users with different roles and states.

Thus, using one user is suitable for basic regression testing, but for comprehensive testing, it is better to use diverse test data.