03. static techniques
- 2. STATIC TECHNIQUES • STATIC TEST TECHNIQUES PROVIDE A POWERFUL WAY TO IMPROVE THE QUALITY AND PRODUCTIVITY OF SOFTWARE DEVELOPMENT. THIS CHAPTER DESCRIBES STATIC TEST TECHNIQUES, INCLUDING REVIEWS, AND PROVIDES AN OVERVIEW OF HOW THEY ARE CONDUCTED. THE FUNDAMENTAL OBJECTIVE OF STATIC TESTING IS TO IMPROVE THE QUALITY OF SOFTWARE WORK PRODUCTS BY ASSISTING ENGINEERS TO RECOGNIZE AND FIX THEIR OWN DEFECTS EARLY IN THE SOFTWARE DEVELOPMENT PROCESS. WHILE STATIC TESTING TECHNIQUES WILL NOT SOLVE ALL THE PROBLEMS, THEY ARE ENORMOUSLY EFFECTIVE. STATIC TECHNIQUES CAN IMPROVE BOTH QUALITY AND PRODUCTIVITY BY IMPRESSIVE FACTORS. STATIC TESTING IS NOT MAGIC AND IT SHOULD NOT BE CONSIDERED A REPLACEMENT FOR DYNAMIC TESTING, BUT ALL SOFTWARE ORGANIZATIONS SHOULD CONSIDER USING REVIEWS IN ALL MAJOR ASPECTS OF THEIR WORK INCLUDING REQUIREMENTS, DESIGN, IMPLEMENTATION, TESTING, AND MAINTENANCE. STATIC ANALYSIS TOOLS IMPLEMENT AUTOMATED CHECKS, E.G. ON CODE.
- 3. REVIEWS AND THE TEST PROCESS THE DEFINITION OF TESTING OUTLINES OBJECTIVES THAT RELATE TO EVALUATION, REVEALING DEFECTS AND QUALITY. AS INDICATED IN THE DEFINITION TWO APPROACHES CAN BE USED TO ACHIEVE THESE OBJECTIVES, STATIC TESTING AND DYNAMIC TESTING. WITH DYNAMIC TESTING METHODS, SOFTWARE IS EXECUTED USING A SET OF INPUT VALUES AND ITS OUTPUT IS THEN EXAMINED AND COMPARED TO WHAT IS EXPECTED. DURING STATIC TESTING, SOFTWARE WORK PRODUCTS ARE EXAMINED MANUALLY, OR WITH A SET OF TOOLS, BUT NOT EXECUTED.
- 4. REVIEW PROCESS • PHASES OF A FORMAL REVIEW IN CONTRAST TO INFORMAL REVIEWS, FORMAL REVIEWS FOLLOW A FORMAL PROCESS. A TYPICAL FORMAL REVIEW PROCESS CONSISTS OF SIX MAIN STEPS: 1. PLANNING 2. KICK-OFF 3. PREPARATION 4. REVIEW MEETING 5. REWORK 6. FOLLOW-UP.
- 5. • ROLES AND RESPONSIBILITIES THE PARTICIPANTS IN ANY TYPE OF FORMAL REVIEW SHOULD HAVE ADEQUATE KNOWLEDGE OF THE REVIEW PROCESS. THE BEST, AND MOST EFFICIENT, REVIEW SITUATION OCCURS WHEN THE PARTICIPANTS GAIN SOME KIND OF ADVANTAGE FOR THEIR OWN WORK DURING REVIEWING. IN THE CASE OF AN INSPECTION OR TECHNICAL REVIEW, PARTICIPANTS SHOULD HAVE BEEN PROPERLY TRAINED AS BOTH TYPES OF REVIEW HAVE PROVEN TO BE FAR LESS SUCCESSFUL WITHOUT TRAINED PARTICIPANTS. THIS INDEED IS PERCEIVED AS BEING A CRITICAL SUCCESS FACTOR. • THE MODERATOR THE MODERATOR (OR REVIEW LEADER) LEADS THE REVIEW PROCESS. HE OR SHE DETERMINES, IN CO-OPERATION WITH THE AUTHOR, THE TYPE OF REVIEW, APPROACH AND THE COMPOSITION OF THE REVIEW TEAM. THE MODERATOR PERFORMS THE ENTRY CHECK AND THE FOLLOW-UP ON THE REWORK, IN ORDER TO CONTROL THE QUALITY OF THE INPUT AND OUTPUT OF THE REVIEW PROCESS. THE MODERATOR ALSO SCHEDULES THE MEETING, DISSEMINATES DOCUMENTS BEFORE THE MEETING, COACHES OTHER TEAM MEMBERS, PACES THE MEETING, LEADS POSSIBLE DISCUSSIONS AND STORES THE DATA THAT IS COLLECTED. • THE AUTHOR AS THE WRITER OF THE DOCUMENT UNDER REVIEW, THE AUTHOR'S BASIC GOAL SHOULD BE TO LEARN AS MUCH AS POSSIBLE WITH REGARD TO IMPROVING THE QUALITY OF THE DOCUMENT, BUT ALSO TO IMPROVE HIS OR HER ABILITY TO WRITE FUTURE DOCUMENTS. THE AUTHOR'S TASK IS TO ILLUMINATE UNCLEAR AREAS AND TO UNDERSTAND THE DEFECTS FOUND.
- 6. • THE SCRIBE DURING THE LOGGING MEETING, THE SCRIBE (OR RECORDER) HAS TO RECORD EACH DEFECT MENTIONED AND ANY SUGGESTIONS FOR PROCESS IMPROVEMENT. IN PRACTICE IT IS OFTEN THE AUTHOR WHO PLAYS THIS ROLE, ENSURING THAT THE LOG IS READABLE AND UNDERSTANDABLE. IF AUTHORS RECORD THEIR OWN DEFECTS, OR AT LEAST MAKE THEIR OWN NOTES IN THEIR OWN WORDS, IT HELPS THEM TO UNDERSTAND THE LOG BETTER DURING REWORK. HOWEVER, HAVING SOMEONE OTHER THAN THE AUTHOR TAKE THE ROLE OF THE SCRIBE (E.G. THE MODERATOR) CAN HAVE SIGNIFICANT ADVANTAGES, SINCE THE AUTHOR IS FREED UP TO THINK ABOUT THE DOCUMENT RATHER THAN BEING TIED DOWN WITH LOTS OF WRITING. • THE REVIEWERS THE TASK OF THE REVIEWERS (ALSO CALLED CHECKERS OR INSPECTORS) IS TO CHECK ANY MATERIAL FOR DEFECTS, MOSTLY PRIOR TO THE MEETING. THE LEVEL OF THOROUGHNESS REQUIRED DEPENDS ON THE TYPE OF REVIEW. THE LEVEL OF DOMAIN KNOWLEDGE OR TECHNICAL EXPERTISE NEEDED BY THE REVIEWERS ALSO DEPENDS ON THE TYPE OF REVIEW. REVIEWERS SHOULD BE CHOSEN TO REPRESENT DIFFERENT PERSPECTIVES AND ROLES IN THE REVIEW PROCESS. IN ADDITION TO THE DOCUMENT UNDER REVIEW, THE MATERIAL REVIEWERS RECEIVE INCLUDES SOURCE DOCUMENTS, STANDARDS, CHECKLISTS, ETC. IN GENERAL, THE FEWER SOURCE AND REFERENCE DOCUMENTS PROVIDED, THE MORE DOMAIN EXPERTISE REGARDING THE CONTENT OF THE DOCUMENT UNDER REVIEW IS NEEDED. • THE MANAGER THE MANAGER IS INVOLVED IN THE REVIEWS AS HE OR SHE DECIDES ON THE EXECUTION OF REVIEWS, ALLOCATES TIME IN PROJECT SCHEDULES AND DETERMINES WHETHER REVIEW PROCESS OBJECTIVES HAVE BEEN MET. THE MANAGER WILL ALSO TAKE CARE OF ANY REVIEW TRAINING REQUESTED BY THE PARTICIPANTS. OF COURSE A MANAGER CAN ALSO BE INVOLVED IN THE REVIEW ITSELF DEPENDING ON HIS OR HER BACKGROUND, PLAYING THE ROLE OF A REVIEWER IF THIS WOULD BE HELPFUL.
- 7. • TYPES OF REVIEW A SINGLE DOCUMENT MAY BE THE SUBJECT OF MORE THAN ONE REVIEW. IF MORE THAN ONE TYPE OF REVIEW IS USED, THE ORDER MAY VARY. FOR EXAMPLE, AN INFORMAL REVIEW MAY BE CARRIED OUT BEFORE A TECHNICAL REVIEW, OR AN INSPECTION MAY BE CARRIED OUT ON A REQUIREMENTS SPECIFICATION BEFORE A WALKTHROUGH WITH CUSTOMERS. IT IS APPARENT THAT NONE OF THE FOLLOWING TYPES OF REVIEW IS THE 'WINNER', BUT THE DIFFERENT TYPES SERVE DIFFERENT PURPOSES AT DIFFERENT STAGES IN THE LIFE CYCLE OF A DOCUMENT. • SUCCESS FACTORS FOR REVIEWS IMPLEMENTING (FORMAL) REVIEWS IS NOT EASYAS THERE IS NO ONE WAY TO SUCCESS AND THERE ARE NUMEROUS WAYS TO FAIL. THE NEXT LIST CONTAINS A NUMBER OF CRITICAL SUCCESS FACTORS THAT IMPROVE THE CHANCES OF SUCCESS WHEN IMPLEMENTING REVIEWS.
- 8. STATIC ANALYSIS BY TOOLS CODING STANDARDS CHECKING FOR ADHERENCE TO CODING STANDARDS IS CERTAINLY THE MOST WELL-KNOWN OF ALL FEATURES. THE FIRST ACTION TO BE TAKEN IS TO DEFINE OR ADOPT A CODING STANDARD. USUALLY A CODING STANDARD CONSISTS OF A SET OF PROGRAMMING RULES (E.G. 'ALWAYS CHECK BOUNDARIES ON AN ARRAY WHEN COPYING TO THAT ARRAY'), NAMING CONVENTIONS (E.G. 'CLASSES SHOULD START WITH CAPITAL C) AND LAYOUT SPECIFICATIONS (E.G. 'INDENT 4 SPACES'). IT IS RECOMMENDED THAT EXISTING STANDARDS ARE ADOPTED. THE MAIN ADVANTAGE OF THIS IS THAT IT SAVES A LOT OF EFFORT. AN EXTRA REASON FOR ADOPTING THIS APPROACH IS THAT IF YOU TAKE A WELL- KNOWN CODING STANDARD THERE WILL PROBABLY BE CHECKING TOOLS AVAILABLE THAT SUPPORT THIS STANDARD. IT CAN EVEN BE PUT THE OTHER WAY AROUND: PURCHASE A STATIC CODE ANALYZER AND DECLARE (A SELECTION OF) THE RULES IN IT AS YOUR CODING STANDARD. WITHOUT SUCH TOOLS, THE ENFORCEMENT OF A CODING STANDARD IN AN ORGANIZATION IS LIKELY TO FAIL. THERE ARE THREE MAIN CAUSES FOR THIS: THE NUMBER OF RULES IN A CODING STANDARD IS USUALLY SO LARGE THAT NOBODY CAN REMEMBER THEM ALL; SOME CONTEXT-SENSITIVE RULES THAT DEMAND REVIEWS OF SEVERAL FILES ARE VERY HARD TO CHECK BY HUMAN BEINGS; AND IF PEOPLE SPEND TIME CHECKING CODING STANDARDS IN REVIEWS, THAT WILL DISTRACT THEM FROM OTHER DEFECTS THEY MIGHT OTHERWISE FIND, MAKING THE REVIEW PROCESS LESS EFFECTIVE.
- 9. • CODE METRICS AS STATED, WHEN PERFORMING STATIC CODE ANALYSIS, USUALLY INFORMATION IS CALCULATED ABOUT STRUCTURAL ATTRIBUTES OF THE CODE, SUCH AS COMMENT FREQUENCY, DEPTH OF NESTING, CYCLOMATIC NUMBER AND NUMBER OF LINES OF CODE. THIS INFORMATION CAN BE COMPUTED NOT ONLY AS THE DESIGN AND CODE ARE BEING CREATED BUT ALSO AS CHANGES ARE MADE TO A SYSTEM, TO SEE IF THE DESIGN OR CODE IS BECOMING BIGGER, MORE COMPLEX AND MORE DIFFICULT TO UNDERSTAND AND MAINTAIN. THE MEASUREMENTS ALSO HELP US TO DECIDE AMONG SEVERAL DESIGN ALTERNATIVES, ESPECIALLY WHEN REDESIGNING PORTIONS OF EXISTING CODE.
- 10. • CODE STRUCTURE THERE ARE MANY DIFFERENT KINDS OF STRUCTURAL MEASURES, EACH OF WHICH TELLS US SOMETHING ABOUT THE EFFORT REQUIRED TO WRITE THE CODE IN THE FIRST PLACE, TO UNDERSTAND THE CODE WHEN MAKING A CHANGE, OR TO TEST THE CODE USING PARTICULAR TOOLS OR TECHNIQUES. IT IS OFTEN ASSUMED THAT A LARGE MODULE TAKES LONGER TO SPECIFY, DESIGN, CODE AND TEST THAN A SMALLER ONE. BUT IN FACT THE CODE'S STRUCTURE PLAYS A BIG PART. THERE ARE SEVERAL ASPECTS OF CODE STRUCTURE TO CONSIDER: • CONTROL FLOW STRUCTURE; • DATA FLOW STRUCTURE; • DATA STRUCTURE.