今天听到有人说，PVC覆盖率也是很重要的一种覆盖率，所以就Google了一下。
Unit Testing with Parameter Value Coverage (PVC)：
Parameter Value Coverage (PVC) is the ability to track coverage of a method based on the common possible values for the parameters accepted by the method.
Current code coverage tools fail to take into consideration the possibility that a value for a parameter is not handled resulting in a bug. However, there may not be any code addressing this value in any way, introducing the possibility of obtaining 100% code coverage or line coverage (LC) without detecting the bug.
