- Preventive testing is very important. Verify documents, design, code at each stage of development to prevent errors from getting in. Use a variety of techniques for this. Code review itself throughs up many defects that may be too difficult to detect by execution of tests. On the other hand, test execution can detect errors that can not be easily detected by code reviews. Therefore, various techniques are complimentary in nature and it is only through their combined use that one can hope to detect most errors.

- Even though development tends to be given more importance than testing. A good test design is perhaps intellectually more challenging than the software design and development. Given reasonable practical limits to the quality of test design in practice, it is easy to understand that why it is difficult to uncover all defects through testing.