What levels of testing have you used in your project?

The following levels of testing are usually applied in projects:

• Unit Testing: testing individual functions or classes.
• Integration Testing: testing the interaction between modules or components.
• System Testing: testing the entire system for compliance with requirements.
• Acceptance Testing: testing the system from the user's perspective, often involving the customer.
• Regression Testing: ensuring that new changes do not break existing functionality.

Depending on the project and methodology, other levels such as load testing or security testing may also be used.