在系统设计阶段可以运用DRR模型进行可测试性度量，本文对集合的势进行了重新的定义，在此基础上建立了定义域和值域的势的比值与软件的可测试度之间的关系。
During system design phase , we can use DRR model to go on testability design . By redefining the cardinality of set , we establish the relationship between the domain / range ratio and the testability metric .
集合的势