Formula to use on Bug Find rate and Bug detection rate are following:
- Bug find rate = Number of failed cases/Total test cases executed in the software or number of failed bugs/total test cases executed.
- Defect detection Percentage = Number of bugs or failed cases discovered by IT team/ [Number of bugs discovered by IT Team+ Number of bugs or tickets being issued by users].
Notes: To measure the success of testing before and after that Functional Testing tester is hired can consider the following:
- First to have that tester improve test coverage and make sure test cases can cover at least acceptance (entry criteria), system integrity, data integrity, functionality, integrated parts, UAT, regression/code impact , performance (stability/reliability), error handling, security, negative test cases. So test cases coverage are strengthened.
- Then identify test cases and break them by phases, such as Smoke test, System testing, Regression Testing, UAT testing.
- Execute testing , discover defects, tag defects in appropriate test phase.
- Calculate DDP (Defect Detection percentage) by phase, comparing the % each phase and justify the effectiveness of the test team.
Example of Bug detection rate:
A software development organization discovered that during the first three months after releasing a software product the users reported about 20 problems. As the test team found 180 problems this means that the DDP equals to 180 / (180 + 20) = 90%. The test process was improved by introducing some formal test design techniques. After the next similar product customers reported only 10 problems during the initial three months. The test team found 190 problems, so the DDP was increased to 190 / (190 + 10) = 95%. The higher effectiveness of the test team had led to rise of the DDP of 5%. The process improvement was considered successful.