Software should be inspected before it is tested: when it comes to finding defects, inspection is much cheaper and faster

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:

Defect removal is the most expensive part of software process. Software defect removal is the most expensive and time-consuming form of work for software.
Inspection is 20 times more efficient. Code inspection is up to 20 times more efficient than testing.
Inspection is nearly twice as fast. 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.
Inspection is 80% faster than testing. Code reading detected about 80% more faults per hour than testing.
Find design defects 6 times faster. Detection of design defects costs 6 times more using testing than by using inspections.
Inspection 4 to 7 times faster than testing. 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.