In the V-model a true requirements testing approach is used, allowing for a definite link between the system requirements and the tests to be used for their confirmation. Clear and concise requirements will lead to thorough testing.
At the earliest stage tests can be developed.
The various tests are run and the results captured and analyzed in depth.
Clear reporting and metrics are produced from the results.
When found, defects are raised and fixed, before iterating through the test again.
Once the functional testing is complete, performance and other non-functional testing can be conducted.