V&V is often portrayed as a single phase of waterfall
Actually a full-life-cycle activity
Requirements must be validated
Designs may be validated & verified
Implementation is tested
final system is tested
maintenence changes are tested
Testing is only one form of V&V, but even it is broken into stages:
Unit Test: Tests of individual subroutines and modules,
Integration Test: Tests of "subtrees" of the total project hierarchy chart (groups of subroutines calling each other).
System Test: Test of the entire system,
Regression Test: Unit/Integration/System tests that are repeated after a change has been made to the code.
Acceptance Test: A test conducted by the customers or their representatives to decide whether to purchase/accept a developed system.
Unit Test: does it work?
Integration Test: does it work?
System Test: does it work?
Regression Test: has it changed?
Acceptance Test: should we pay for it?