When should testing end? What are the completion criteria?

Testing should end when predefined completion criteria are met. The main criteria are:

• All planned test cases are executed and passed (or all critical defects are identified and documented).
• Requirements and functionality coverage is achieved according to the plan.
• The number of open bugs is below an acceptable threshold (e.g., no critical or blocking errors).
• All regression tests are completed after defect fixes.
• All mandatory types of testing (functional, integration, load testing, etc.) are passed if they are planned.
• Testing time and budget are exhausted, and further testing does not provide significant benefits.

Thus, testing ends when the product quality meets the requirements and the risks are considered acceptable for release.