Software should be inspected before it is tested: when it comes to finding defects, inspection is much cheaper and faster.
Research has yielded these findings:
- Software defect removal is the most expensive and time-consuming form of work for software.
- NASA's Software Engineering Laboratory found that code inspection detected about 3.3 defects per hour of effort, compared to 1.8 errors per hour of testing effort.
- The average cost of finding an error using code inspections is 3.5 staff hours compared to 15-25 hours to find each error through testing.