1. Claus Brabrand, ITU, Denmark Feb 03, 2009TESTING Testing Claus Brabrand [ brabrand@itu.dk ] ( “FÅP” First-year Project Course, ITU, Denmark )

2. [ 2 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Outline Motivation Why bother with testing? The Psychology of Testing What is the goal of testing? The Testing Process What is relation to other programming-related tasks? Bugs Important properties of bugs Implementation vs. Specification: Formal definition of a bug

3. [ 3 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Learning & Exam Goals ”Product”: ”Oral Exam”:

4. [ 4 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Software Errors Therac-25 Radiation Therapy ’85-’87 Massive overdoses (6 deaths / amputations)! Patriot Missile Guidance System ’91 (Gulf War 1.0) Accumulating rounding errors  deaths Ariane V ’96 (one of the most expensive bugs, ever) Conversion from 64-bit float to 16-bit signed int

5. [ 5 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 z z Software Errors (cont’d) Train Control System ’98 (Berlin) Train cancellations Mars Pathfinder July ’97 Periodic resets Win95/98 w/ 3 rd -Party Device Drivers late ’90es Dysfunction (“blue screen of death”)!...on mars!

6. [ 6 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009  Software Errors (cont’d) Mobile Phones ’00-… Freeze and odd behaviors (really annoying)! Cruise Control System Model ’86 (Grady Booch) Accellerated after car ignition  car crashes Baggage Handling System ’94-’95 (at Denver Int’l Airport) $ 360,000,000 USD

7. [ 7 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009  …and what about?! Surgical Laser Control System Oops…! Air Plane Control System Dysfunction (plane crash)! Nuclear Powerplant Control System Core melt-down (“China-syndrome”)!

8. [ 8 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Outline Motivation Why bother with testing? The Psychology of Testing What is the goal of testing? The Testing Process What is relation to other programming-related tasks? Bugs Important properties of bugs Implementation vs. Specification: Formal definition of a bug

9. [ 9 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Testing Incomplete Process A program has: many possible valid inputs many possible invalid inputs Hence: 8 8 Testing can never prove absence of errors! Testing is an incomplete process!

10. [ 10 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 The Psychology of Testing X Goal: test a program to show that it works …we might as well stop before we even start! :-( Homo Sapiens are ”goal oriented” (steer towards goal)! :-) ”Testing is the process of demonstrating that errors are not present.” ”The purpose of testing is to show that a program performs its intended functions correctly.” [cf. ”The Art of Software Testing” (Chap. 2), Glenford J. Myers, 1979] ”Testing is the process of establishing confidence that a program does what it is supposed to do.”

11. [ 11 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009   successful test case unsuccessful test case Problematic terminology:   successful test case unsuccessful test case Much better terminology: Psychology of Testing (cont’d) Goal: find as many errors as possible Note: realistically assumes errors are present Constructive goal (actually destructive) ”Testing is the process of executing a program with the intent of finding errors.” vs [cf. ”The Art of Software Testing” (Chap. 2), Glenford J. Myers, 1979]

12. [ 12 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Constructive vs. Destructive Thinking Constructive thinking: (e.g., programming) ”Test-to-pass” Often not a good idea to ”test” your own code :-( Destructive thinking: (e.g., testing) ”Test-to-fail” Often better to test/break someone else’s code :-) FAAP Recommendation:  Have another group help you test your FAAP group ”product”

13. [ 13 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Tester’s Goal The goal of a software tester is: Testers (therefore) often aren’t the most popular members of a project team - 1) “to find bugs”; - 2) “find them as early as possible”; and - 3) “make sure they get fixed” [R.Patton, “Software Testing”, p. 19] [cf. ”Software Testing”, R.Patton, p.19]

14. [ 14 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Outline Motivation Why bother with testing? The Psychology of Testing What is the goal of testing? The Testing Process What is relation to other programming-related tasks? Bugs Important properties of bugs Implementation vs. Specification: Formal definition of a bug

15. [ 15 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 ISO 9126 Maintainability Reliability Usability Portability How robust is the SW wrt. external network failures, ’^C’,...? How easy is the SW to understand? …and use? How easy is it to transfer and adapt SW to new environment / platform? How easy is it to modify the SW? And fix errors? Software Quality International evaluation standard Functionality Efficiency ISO 9126 Does the SW do what it’s supposed to? Does it work as intended? How much time/memory/space/- bandwidth/… does the SW consume?

16. [ 16 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Testing vs. Debugging? Testing vs. Debugging?: Functionality:Efficiency: Quality Assurance: (Functionality) Testing (Performance) Testing Diagnosis:Profiling Purpose: Regarding: Debugging

17. [ 17 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Testing vs. Debugging (cont’d) Evaluate test results Fix problem (reprogram) Functionality Testing Quality assurance: Perform (functionality) test Debugging Diagnosis: Determine problem? 0110 1021 Program: 0110 1011 (greater confidence!)   SYSTEMATIC Document test results (confidence?!?) Re- 0110 1011

18. [ 18 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Performance Testing vs. Profiling Evaluate test results Improve program (reprogram) Performance Testing Quality assurance: Perform (efficiency) test Profiling Diagnosis: Determine problem? 0110 1021 Program: 0110 1011   (greater confidence!) Document test results (confidence?!?) Re- SYSTEMATIC 0110 1011

19. [ 19 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 White-box vs. Black-box Test White-box Testing: (aka., ”structural testing”) (aka., ”internal testing”) Test focus: source code Black-box Testing: (aka., ”behavioral testing”) (aka., ”external testing”) (aka., ”input-ouput testing” ) Test focus: specification (or intention) Complementary Approaches!!! n = in(); n = n/2; odd(n) n = 3*n+1; out(n); tt ff ~ ? programspec

20. [ 20 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Exercise: which is (usually) ”best” - and why? A) white-box testing ; black-box testing ; (i.e., white-box testing first) B) black-box testing ; white-box testing ; (i.e., black-box testing first) Answer: ’B’ Settle overall impl ~ spec problems first Before zooming in on details of impl Exercise …or…

21. [ 21 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 ”Software Testing” (R. Patton) Background reading: ”Software Testing”, Ron Patton, Sams Publishing, 2006 Part II (pp. 53 – 123); ”Testing Fundamentals”: ”Examining the Code” (chapter 6) ”Examining the Spec.” (chapter 4) ”Testing w/ Blinders On” (chapter 5) ”Testing w/ X-ray Glasses” (chapter 7) Dynamic (running program) Static (w/o running prg) -testing Time: Type:

22. [ 22 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Outline Motivation Why bother with testing? The Psychology of Testing What is the goal of testing? The Testing Process What is relation to other programming-related tasks? Bugs Important properties of bugs Implementation vs. Specification: Formal definition of a bug

23. [ 23 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Definition: ”bug” Main entry: 2 bug Pronunciation: /’bəg/ Function: noun Etymology: origin unknown Date: 1622 1 a: an insect or other creeping or crawling invertebrate (as a spider or centipede) b: any of several insects (as the bedbug or cockroach) commonly considered obnoxious c: any of an order (Hemiptera and especially its suborder Heteroptera) of insects that have sucking mouthparts, forewings thickened at the base, and incomplete metamorphosis and are often economic pests —called also true bug 2: an unexpected defect, fault, flaw, or imperfection 3 a: a germ or microorganism especially when causing disease b: an unspecified or nonspecific sickness usually presumed due to a bug 4: a sudden enthusiasm 5: enthusiast 6: a prominent person 7: a crazy person 8: a concealed listening device 9: a weight allowance given apprentice jockeys

24. [ 24 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 ”The Harvard Mark II Bug” Photo of first actual ”bug”: “The first documented computer bug was a moth found trapped between points at Relay # 70, Panel F, of the Mark II Aiken Relay Calculator while it was being tested” Harvard University, Sep. 9, 1947

25. [ 25 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Example of a Bug :-) Hej Claus, A propos test og datoberegninger: Fredag morgen mente min PDA kalender (Microsoft Windows CE) at vi skrev lørdag 1. marts. Jeg stillede selvfølgelig tålmodigt uret tilbage til fredag 29. februar 2008 (dette fandt sted på et møde hos Microsoft i Vedbæk ;-) Lørdag formiddag startede den så med at vise min (ret tomme) kalender for august 2049. Det indbyggede ur stod på 1. januar 1601. Ahem. Peter

26. [ 26 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Terminology (for ’Bugs’) ”Severe conditions”: Fault Failure Defect ”Unintended operation”: Anomaly Incident Variance Feature (sounds intended) ”Generic terms”: Problem Error Bug Typically imply blame; as in: - ”it was his fault” Famous quote: - ”It’s not a bug, it’s a feature” we’ll use these terms

27. [ 27 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Bugs Bugs often occur in groups: If you find one, chances are there are more nearby This property useful when testing program parts: i.e., figuring out where to concentrate testing efforts Not all bugs will be fixed: Too costly? Too risky? Not ”cost-effective”? Cause unknown?

28. [ 28 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Cost of (Fixing) Bugs Cost of bugs increases exponentially (over time): (log) specdesigncodetestrelease $1 $100 $10,000 $1,000,000 $100,000,000 [cf. ”Software Testing”, R.Patton, p.18] cost phase

29. [ 29 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 ”The Pesticide Paradox” ”The pesticide paradox”: ”The more you test a software, the more immune it becomes to your tests” B.Beizer, “Software Testing Techniques”, 1990

30. [ 30 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Bug Kinds (diff. kinds of errs) Syntactic errors: Mal-formed program: Semantic errors: Symbol errors Type errors Other semantic errors: (e.g. uninitialized vars) Logical errors: Compiler: ”no errors” int square(int x) { return x*x } *** syntax error at line 2 ’;’ expected int square(int x) { return n*n; } *** symbol error at line 2 undefined variable ”n” int square(float x) { return x*x; } *** type error at line 2 function returns float, not int int square(int x) { return x+x; } no errors found!!!

31. [ 31 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Outline Motivation Why bother with testing? The Psychology of Testing What is the goal of testing? The Testing Process What is relation to other programming-related tasks? Bugs Important properties of bugs Implementation vs. Specification: Formal definition of a bug

32. [ 32 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Definition: ”Bug” A ”bug” is a relation between: Specification & Implementation Whether or not specification is: Explicit or Implicit Written or Oral Formal or Informal (e.g., ”product spec” vs. ”back-of-envellope”) implementation (aka., ’program’) specification (aka., ’spec’) ~ bug

33. [ 33 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Specification A spec states things an impl…: Should do! Shouldn’t do! Unspecified? (’unclear’, ’unmentioned’, or ’left open’) Should do! Shouldn’t do! Unspecified? S Specs are often intentionally under-specified. It’s often better to not ”prematurely commit” to a particular solution (by specifying exactly how a task should be done) – and instead just state which overall tasks the system should do.

34. [ 34 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Formal Definition: ”Bug” A (software) bug occurs when: 1. Impl doesn’t do sth spec says it should: 2. Impl does sth spec says it shouldn’t: 3. Impl does sth spec doesn’t mention: 4. Spec doesn’t mention sth, but should: 5. Impl is hard to understand/use by user(s): ~ ~ ?! (or does it incorrectly) I S I S S I ?! I S [cf. ”Software Testing”, R.Patton, p.15] ! ~ ideal

35. [ 35 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Consequences… Consequently, …: ”Additional functionality”? e.g., a calculator which also does square root (but wasn’t supposed to) ”Easter egg”? e.g., hit [Alt+Shift+2] in Solitaire to win game

36. [ 36 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Exercise Exercise: A) R.Patton interprets as (”spec := impl”):  trivially no bugs in impl ! (according to [own] definition #1,#2,#3) B) More sensible to interpret as ”no spec”:  entire impl is essentially one big bug ! (…according to definition #3+#4) ”Because the software is already complete, you have the perfect specification – the product itself” [R.Patton, ”Software Testing”, p.31] ”an impl w/o a spec” ? bug ~

37. Claus Brabrand, ITU, Denmark Feb 03, 2009TESTING Exercise on Testing Intro to test cases

38. [ 38 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Testing…: Testing is easy: (e.g., ”random experimentation”) Testing well is not easy; requires: A SYSTEMATIC approach Test case…: production evaluation documentation

39. [ 39 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Representative? Comprehensive? Quality? Quantity? …? Appropriate Test Cases?    

40. [ 40 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Myers’ 10 Testing Principles 1) expected output is part of a test case 2) avoid testing own program 3) avoid testing own (organization’s) program 4) thoroughly inspect result of each test case 5) also write ”invalid / unexpected” test cases 6) also check: doesn’t do what not supposed to 7) avoid throw-away test cases 8) never assume no errors when making test cases 9) Prob(more errors) ~ Prob(#errors already found) 10) Testing is creative+intellectually challenging task [cf. ”The Art of Software Testing” (Chap. 2), Glenford J. Myers, 1979] a) destructive vs. constructive mode b) can be overall misunderstandings also wrt. program parts instead: systematic ”regression testing”! a) … b) …

41. [ 41 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Exercise: Triangle Test Test Equilateral triangle (T-3): All three sides have equal length Isosceles triangle (T-2): Two sides have equal length Scalene triangle (T-1): All sides have different length Q: Which test cases should we use? E.g., (1,1,1), (2,2,2), (3,3,3), (4,4,4), (5,5,5), …? enum Triangle { EQUILATERAL, ISOSCELES, SCALENE } Triangle isTriangle(int a, int b, int c); The program reads three integer values from an input dialog. (The three values represent the lengths of the sides of a triangle.) The program displays a message that states whether the triangle is: - equilateral, isosceles, or scalene. ligebenet ligesidet atypisk trekant(?)

42. Claus Brabrand, ITU, Denmark Feb 03, 2009TESTING Groups FAAP’09 Project Groups

43. [ 43 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 Considerations (Group Formation) Considerations; e.g.: a) Balance Introverts and Extroverts: Too many intros  few discussions / limited exchange Too many extros  Blah blah blah… b) Avoid ”strategist-strategist” clashes: More likely to ”clash” c) Balance heterogeneously wrt. ”MBTI” Many different inputs d) Avoid ”old group mates” in same group Learn to work with ”new people” Avoid sub-groups (aka, cliques)

44. [ 44 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 FAAP’09 Groups ISTJ ( Inspector ) ISTP ( Crafter ) ESTP ( Promoter ) ESTJ ( Supervisor ) ISFJ ( Protector ) ISFP ( Composer ) ESFP ( Performer ) ESFJ ( Provider ) INFJ ( Counselor ) INFP ( Healer ) ENFP ( Champion ) ENFJ ( Teacher ) INTJ ( Mastermind ) INTP ( Architect ) ENTP ( Inventor ) ENTJ ( Field Marshal ) SN TFT I E P J J

45. [ 45 ] Claus Brabrand, ITU, Denmark TESTINGFeb 03, 2009 White:  Anna  Charlotte  Jesper  Kasper  Peter P.M Yellow:  Frederik J.  Mik  Mikkel  Mohammad  Peter A.N. Orange:  Janne  Mads T.P.  Oliver  Sebastian  Thuy Red:  David  Frederik W.  Jakob  Mads H.J.  Pelle Green:  Bo  Dorte  Erla  Ida  Kristian K.M Blue:  Asger  Lasse  Niels  Søren  Torben Brown:  Christian T.  Joakim  Johannes  Nikolaj D.L.  Simon Black:  Jon  Mads B.A.  Nikolaj S.  Nikolas  Rene Groups (FAAP’09)