Software testing is one of the most expensive phases in the software life cycle. Even for the best commercial grade software, it seldom contains fewer than 100 faults per million lines of code. These faults result in failures and costs for customers which software manufacturers are motivated to avoid. It is not unusual for manufacturers to spend 40% or more of their software budgets on testing in an effort to eliminate these faults. Hence, it is very important to provide a solution, supported by tools, which not only can reduce the cost but also improve the quality. The authors describe their effort in developing an Ada program instrumentation environment, Ada-PINE, for testing real time Ada programs. This tool can help developers and testers in many ways such as determining how well the software has been tested, displaying the code that has not been executed, and improving the code coverage in the most effective way. It can also conduct test set minimization with respect to code coverage and select effective fault-revealing regression tests.