Studying the effects of code inspection and structural testing on software quality

The paper contributes a controlled experiment to characterize the effects of code inspection and structural testing on software quality. Twenty subjects performed sequentially code inspection and structural testing using different coverage values as test criteria on a C-code module. The results of this experiment show that inspection significantly outperforms the defect detection effectiveness of structural testing. Furthermore, the experimental results indicate little evidence to support the hypothesis that structural testing detects different defects, that is, defects of a particular class, that were missed by inspection and vice versa. These findings suggest that inspection and structural testing do not complement each other well. Since 39 percent (on average) of the defects were not detected at all, it might be more valuable to apply inspection, together with other testing techniques, such as boundary value analysis, to achieve a better defect coverage. We are aware that a single experiment has many limitations and often does not provide conclusive evidence. Hence, we consider this experiment a starting point and encourage other researchers to investigate the optimal mix of defect detection techniques.