Defect Detection Efficiency: Test Case Based vs. Exploratory Testing

This paper presents a controlled experiment comparing the defect detection efficiency of exploratory testing (ET) and test case based testing (TCT). While traditional testing literature emphasizes test cases, ET stresses the individual tester´s skills during test execution and does not rely upon predesigned test cases. In the experiment, 79 advanced software engineering students performed manual functional testing on an open-source application with actual and seeded defects. Each student participated in two 90-minute controlled sessions, using ET in one and TCT in the other. We found no significant differences in defect detection efficiency between TCT and ET. The distributions of detected defects did not differ significantly regarding technical type, detection difficulty, or severity. However, TCT produced significantly more false defect reports than ET. Surprisingly, our results show no benefit of using predesigned test cases in terms of defect detection efficiency, emphasizing the need for further studies of manual testing.