We don't know of a test method that can prove the absence of bugs in any nontrivial system.
Testing can only prove the presence of bugs.
Involving clients and users in all stages of testing ensures that the system will meet their expectations. That is why we start testing very early in the project and require that your team and users participate in these tests. We conduct a few formal and several informal reviews throughout the project. During Analysis, we conduct CRC card sessions to ensure that a common vocabulary and understanding of requirements exists between users and developers. We also validate the domain model against the requirements.