To fulfill software requirements and to satisfy the customer, software must be tested by all angles of users and developer .But the question is that when to stop testing or whether it is enough to test software, if it not tested properly by software engineer then it is handover to customer, if we want to give quality s/w product then we must calculate software reliability as it one of quality measure. s/w reliability is probability of failure free operation of software. usually tester focus on testing functional or normal behavior of units of s/w and it is in developer’s environment but software reliability focus on operational behavior of software in natural setting that is in presence of customers and users, it is need of software community to combine both functional and operational approach so that testing should be done effectively and reliability should be accurately measured. In this paper issue is highlighted that using metrics defect density and statistical modeling software reliability can be measured.
