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Quality AssuranceIntroduction to Part II

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Introduction to Part II

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Christof Lutteroth/2012 • From Berlin, Germany

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y• Some years ago this was the first lecture given by me

(you can watch the old lectures on video)M h i t t HCI SE t l

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• My research interests: HCI, SE tools, …• Contact details:

christof@cs auckland ac nz

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christof@cs.auckland.ac.nzPhone 373-7599 84478Office: 303 - 494 (4th level CompSci building)

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• If you have questions, come to my office at any time

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Introduction to Part II

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Introduction to Part II

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Quality means doing it right h i l ki

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Why not just Dynamic Detection of Defects?

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Detection of Defects?• First half mostly about dynamic detection of defects

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y y• Can be time consuming, costly, complicated…but is

necessary!!!R i ( ti ll ) i t l d

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• Requires a (partially) running system already. What if we don’t have it yet?

• Usually in the implementation stage of a project

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Usually in the implementation stage of a project.What if the defect has its origin in the specification or design?

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• What if our test cases contain defects?

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How can we avoid defects in the first place?

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Static Detection of Defects/2012

• If we cannot avoid defects, detect them as early as

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, ypossible

• “Static” means before runtime

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• Most compilers detect many type errors (type systems), other tools detect even more errors

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• The more specification we give, the more we can verify; formal specification languages (e.g. Z, Alloy, H C l l s)

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e Hoare Calculus)• Sad result from theory:

some errors cannot be detected statically!!!

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prohibit even code that might be an error

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prohibit even code that might be an error

Best Practices/2012 • Avoiding the mistakes that cause defects by “doing

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g y gthe right thing” – Software development processes:

how to undertake a software project

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how to undertake a software project– Software tools:

use the best suitable tools to get the best results

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use the best suitable tools to get the best results– Design & coding guidelines:

how to avoid design/programming mistakes

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• Learn from other’s experience & mistakes (not as effective as learning from own mistakes, but

)

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k saves time )• But: what works for others does not necessarily work

for you (nothing can replace your own experience)

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for you (nothing can replace your own experience)

/2012

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Software Development

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Processes

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“I love it when a plan

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eXtreme Programming (XP)

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(XP) 2

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Don Wells

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• Generic plan of how to conduct a project

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• Relies heavily on feedback about the software

Rational Unified Process (RUP)

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(RUP) 2

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• Comprehensive process framework

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• Comprehensive process framework• Used esp. For large projects

/2012

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Software Development Tools

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Software Development Tools

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First we shape our tools and th t l h

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Software Tools/2012 • Humans are necessary for creative,

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yintelligent tasks

• Tools can support such tasksI d ti it ith f l

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– Increase productivity with useful functionality

– Guide the developer (e g context help)

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Guide the developer (e.g. context help)– Avoid defects

H f h hl

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• Tools can automate such tasks

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creative work

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11– Avoid defects introduced by the human factor

Modeling tools/2012

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GUI Builders/2012

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Version Control Systems/2012

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gy g gdevelopers do on a common repository

• Changes create new version of the changed files

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• Old versions are always accessibleDevelopers

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Developers

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Version 5Working

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Version 2Version 3

Version 4Copy

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Copy

Version Control SystemsExample: Subversion

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Example: Subversion 2

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Build ToolsExample: make

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Example: make 2

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calc: main o math o

Dependency graph

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calc: main.o math.o g++ main.o math.o -o calc calc

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main.o: main.cpp g++ -c main.cpp

main.o math.o

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math.o: math.cpp math.hg++ -c math.cpp

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clean: rm * o

main.cpp math.hmath.cpp

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rm .o

Documentation ToolsExample: JavaDoc

/2012

Example: JavaDocpublic class Stack {/**

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* Pushes an item on to * the top of this stack. * @param item the item to be pushed.

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*/ public void push(Objec item){

this.elements.add(item);}

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/** * Removes the object at the top* of this stack and returns that * object

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e object. * @return The object at the top * of this stack. * @exception NoSuchElementException

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public Object pop() throws NoSuchElementException {

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throws NoSuchElementException { // ...

} }

Generators/2012

JSPGeneration of a web UI

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GeneratorJSP

JSPJSP

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JSP

Generation of Java classes

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ClassClass

Class

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Class

Generation of language parsers

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GeneratorSource code

for parserLanguagegrammar

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grammar

/2012

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Coding Principles

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Coding Principles

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“Use the source, Luke”

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Coding Style/2012

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main(a,b){while((a=getchar())+1)

putchar((b=64^a&223)

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|(b+12)%26+1:a);}

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• International Obfuscated C Code Contest (ioccc.org)• Coding style guidelines help to achieve clear,

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Coding Principles/2012

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vsImplementation

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Today’s summary/2012

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• Dynamic detection of defects (e.g. testing,

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y ( g g,debugging) is necessary, but not enough

• Static checking (e.g. with type systems) can detect

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some defects before runtime • We can avoid defects by following best practices of

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software development and using tools• Software tools support the developer in performing

ti t sks d t t ti t sks

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This week no tutorial, no lab.Friday: Part 4 Exhibition!

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Friday Part 4 Exhibition!

Quiz/2012

Q

1. How can defects be avoided?

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Name and explain 3 examples.

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2. What tools exist for supporting software development? Name 5 examples and explain what they do

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Name 5 examples and explain what they do.

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