claus brabrand, itu, denmark feb 03, 2009testing testing claus brabrand [ [email protected] ] (...

Claus Brabrand, ITU, Denmark Feb 03, 2009TESTING

Testing

Claus Brabrand[ [email protected] ]

( “FÅP” First-year Project Course, ITU, Denmark )

[ 2 ]Claus Brabrand, ITU, Denmark TESTING Feb 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


Learning & Exam Goals

”Product”:

”Oral Exam”:


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


zzzz

Software Errors (cont’d)

Train Control System ’98 (Berlin)

Train cancellations

Mars Pathfinder July ’97

Periodic resets

Win95/98 w/ 3rd-Party Device Drivers late ’90es

Dysfunction (“blue screen of death”)!

...on mars!


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


…and what about?!

Surgical Laser Control System

Oops…!

Air Plane Control System

Dysfunction (plane crash)!

Nuclear Powerplant Control System

Core melt-down (“China-syndrome”)!


Outline







Testing Incomplete Process

A program has: many possible valid inputs many possible invalid inputs

Hence:

88

Testing can never prove absence of errors!

Testing is an incomplete process!


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.”


successfultest case

unsuccessfultest case

Problematic terminology:

successfultest case

unsuccessfultest 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



Constructive vs. DestructiveThinking 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”


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]


Outline







ISO9126

Maintainability

ReliabilityUsability

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 QualityInternational 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?


Testing vs. Debugging?

Testing vs. Debugging?:

Functionality: Efficiency:

Quality Assurance:(Functionality)

Testing(Performance)

Testing

Diagnosis: Profiling

Purpose:

Regarding:

Debugging


Testing vs. Debugging (cont’d)

Evaluate test resultsFix problem(reprogram)

FunctionalityTesting

Quality assurance:

Perform (functionality) test

Debugging

Diagnosis:

Determine problem?

01101021Program:

01101011

(greater confidence!)

SYSTEMATIC

Document test results

(confidence?!?)

Re-

01101011


Performance Testing vs. Profiling

Evaluate test resultsImprove program(reprogram)

Performance Testing

Quality assurance:

Perform (efficiency) test

Profiling

Diagnosis:

Determine problem?

01101021Program:

01101011

(greater confidence!)Document test results

(confidence?!?)

Re-

SYSTEMATIC

01101011


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 ~?program spec


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…


”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)

”Examiningthe 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 -testingTime:

Type:


Outline







Definition: ”bug”Main entry: 2bug

Pronunciation: /’bəg/

Function: noun

Etymology: origin unknown

Date: 16221 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 <e.g., “the software was full of bugs”>

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 <a camera bug>

6: a prominent person

7: a crazy person

8: a concealed listening device

9: a weight allowance given apprentice jockeys


”The Harvard Mark II Bug”

Photo of firstactual ”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


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


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


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?


Cost of (Fixing) Bugs

Cost of bugs increases exponentially (over time):

(log)

spec design code test release

$1$100

$10,000

$1,000,000

$100,000,000


cost

phase


”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


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!!!


Outline







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


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.


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)IS

I S

S I

?!I

S


!~ideal


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


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~


Exercise on Testing

Intro to test cases


Testing…:

Testing is easy: (e.g., ”random experimentation”)

Testing well is not easy; requires: A SYSTEMATIC approach Test case…:

production evaluation documentation


Representative?

Comprehensive?

Quality?

Quantity?

…?

Appropriate Test Cases?


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


a) destructive vs. constructive modeb) can be overall misunderstandings

also wrt. program parts

instead: systematic”regression testing”!

a) …b) …


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(?)


Groups

FAAP’09 Project Groups


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)


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 )

S N

T F T

I

E

P

J

J


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)

claus brabrand, itu, denmark feb 03, 2009testing testing claus brabrand [ [email protected] ] (...

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