1. Jump to first page (C) 1998, Arun Lakhotia 1 Quality Assurance: Reviews and Walkthroughs Arun Lakhotia University of Southwestern Louisiana Po Box 44330 Lafayette, LA 70504, USA arun@cacs.usl.edu

2. Jump to first page (C) 1998, Arun Lakhotia 2 Reference n Steve McConnell, Code Complete, Microsoft Press, 1993. u See Chapter 24 and parts of Chapter 23 n Keywords u Quality attributes u Faults, failures u Review u Walkthrough

3. Jump to first page (C) 1998, Arun Lakhotia 3 Terminology n Failure u Externally observable incorrect behavior n Fault (bug, defect) u Internal cause of the external failure n Fix u Change the internals or environment to remove the failure

4. Jump to first page (C) 1998, Arun Lakhotia 4 Software quality characteristics n Correctness n Usability n Efficiency n Reliability n Integrity n Adaptability n Robustness n Accuracy n Maintainability n Flexibility n Portability n Reusability n Readability n Testability n Understandabi lity

5. Jump to first page (C) 1998, Arun Lakhotia 5 Quality trade-offs n Correctness u Functioning exactly to specifications n Adaptability u Used in an environment or application for which it is not designed n Robustness u Functioning in the presence of invalid inputs Increasing one may decrease the other

6. Jump to first page (C) 1998, Arun Lakhotia 6 Quality improvement techniques n Dynamic -- by executing u Unit testing u Functional testing n Static -- without executing u Inspection u Code walkthroughs u Extern audit u Code reading u Desk check u Proof of correctness n Organizational u Written quality objectives u Development process u Explicit QA activity u Change control process

7. Jump to first page (C) 1998, Arun Lakhotia 7 Effectiveness of QA techniques u Percent of total defects found in the life of a system by a technique n QA step Mean n Desk checking (Design) - 35% n Informal review - 40% n Formal inspection (Design) - 55% n Formal inspection (Code) - 60% n Prototyping - 65% n Desk-checking code - 40% n Unit testing - 25% n Function testing - 35% n Integration testing - 45% n Field testing - 50%

8. Jump to first page (C) 1998, Arun Lakhotia 8 Cost of finding defects n In the beginning static techniques are more expensive n Overtime static techniques are cheaper and find higher number of bugs n Code reading found 80% more faults per hour

9. Jump to first page (C) 1998, Arun Lakhotia 9 Effectiveness of QA techniques n No single technique finds greater than 65% (mean) errors n Unit testing - only 25% n Combination of techniques needed u Combining any two techniques may increase the detection rate two fold n Static and dynamic processes find different types of defects n Dynamic techniques find about 60%

10. Jump to first page (C) 1998, Arun Lakhotia 10 Cost of fixing defects n How defects are found and the cost of fixing them. n Inspection u Finding and fixing in one step u 3 hours per defect n Testing u Find failure u Find case of failure (bug) and fix u Two steps u 12 hours per defect

11. Jump to first page (C) 1998, Arun Lakhotia 11 Static techniques n Also called Reviews u Formal Inspection u Code walkthroughs u Code reading

12. Jump to first page (C) 1998, Arun Lakhotia 12 Formal inspection n “Formal” u Well defined procedure u Well defined roles u Well defined expectations u Well defined output

13. Jump to first page (C) 1998, Arun Lakhotia 13 Formal Inspection: Roles n Moderator n Author n Reviewers n Scribe n but not Management u The roles of moderator, author, and reviewer should be played by different people.

14. Jump to first page (C) 1998, Arun Lakhotia 14 Formal Inspection: Process n Planning u Author gives material to moderator u Moderator identifies reviewers, provides them F Material F Checklist n Overiew: Author gives overview n Preparation: u Reviewer work independently and review material u Prepare a list of problems u Based on checklist n Inspection meeting u Go over the material at a reasonable pace u Identify defects u Do not fix u Scribe takes notes n Report; Rework; Followup

15. Jump to first page (C) 1998, Arun Lakhotia 15 Code walkthroughs n Author u identifies possible reviewers u Gives them material n Reviewers u Read the code to find defects u Give feedback in a meeting u Emphasize on defect detection, not removal

16. Jump to first page (C) 1998, Arun Lakhotia 16 Code Reading n Author u gives code to code readers n Readers u read it independently u prepare a list of problems identified u Give the list to the developer F in meeting F or outside meeting