When can it be said that testing of a particular feature is complete?

Testing a specific feature can be considered complete when the following conditions are met:

• All planned test cases for this feature have been successfully passed or all critical bugs have been identified and documented.
• All main usage scenarios and boundary cases are covered.
• No new serious defects related to the feature have been found within a certain period (stability).
• Testing coverage requirements have been fulfilled (functional, integration, regression).
• The team (testers, developers, managers) has agreed on the readiness of the feature for release.

Thus, the end of testing is not just passing tests, but achieving an acceptable level of quality and stability, confirmed by results and agreement.