Test Driven Developmenthpac.rwth-aachen.de/teaching/sem-lsc-12/TDD.pdfMotivation Test Driven...
35
Test Driven Development Seminar on Languages for Scientific Computing Albert J. Helligrath December 13, 2012
Transcript of Test Driven Developmenthpac.rwth-aachen.de/teaching/sem-lsc-12/TDD.pdfMotivation Test Driven...
Test Driven DevelopmentSeminar on Languages for Scientific Computing
Albert J. Helligrath
December 13, 2012
Motivation Test Driven Development Analysis Conclusion
1 Motivation
2 Test Driven Development
3 Analysis
4 Conclusion
TDD 2 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Costs of Errors
Maiden Flight of Ariane 5 (1996)
unhandled exception duringfloat-int conversion (overflow)
error message misinterpreted ascontrol commands
purposeful blowing-up
costs: 370 Million $
TDD 3 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Software Quality Assurance
increase quality,reduce errors
avoid errors (constructive)orfind and eliminate errors
verification to expensive,practical solution:minimum effort,maximum damage reduction
Quality
The degree to which a system,component, or process meetsspecified requirements.ISO/IEC/IEEE 24765:2010
Error
The difference between acomputed, observed, or measuredvalue or condition and the true,specified, or theoretically correctvalue or condition.ISO/IEC/IEEE 24765:2010
TDD 4 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Software Quality Assurance
increase quality,reduce errors
avoid errors (constructive)orfind and eliminate errors
verification to expensive,practical solution:minimum effort,maximum damage reduction
Quality
The degree to which a system,component, or process meetsspecified requirements.ISO/IEC/IEEE 24765:2010
Error
The difference between acomputed, observed, or measuredvalue or condition and the true,specified, or theoretically correctvalue or condition.ISO/IEC/IEEE 24765:2010
TDD 4 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Test
goal: find an error
effective testing:test frameworktest process
but: tests skipped first,programmers don’t like testing
Testing
The process of operating a system orcomponent under specified conditions,observing or recording the results, andmaking an evaluation of some aspectof the system or component.IEEE-Definition
TDD 5 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Test
goal: find an error
effective testing:test frameworktest process
but: tests skipped first,programmers don’t like testing
Testing
The process of operating a system orcomponent under specified conditions,observing or recording the results, andmaking an evaluation of some aspectof the system or component.IEEE-Definition
TDD 5 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
1 Motivation
2 Test Driven Development
3 Analysis
4 Conclusion
TDD 6 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Test Driven Development
goal: assure testing, avoid defects earlyapproach: ”test first”
TDD introduced as extreme programming practice
iterative steps,short cycle
TDD 7 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Test Driven Development
goal: assure testing, avoid defects earlyapproach: ”test first”
TDD introduced as extreme programming practice
iterative steps,short cycle
TDD 7 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Steps of TDD
1 Identify missing functionalityrequires analysis of specificationsplits the problem into smaller pieces
2 Write a failing unit testguarantees code to be testedgood unit test:fast, runs in isolation,easy to read, uses real datafailing tests the test
3 Write just enough code to pass itfake implementation, inelegant wayonly pass the test, refactor later
4 Refactor and Test againcode smell?make the bar green
TDD 8 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Steps of TDD
1 Identify missing functionalityrequires analysis of specificationsplits the problem into smaller pieces
2 Write a failing unit testguarantees code to be testedgood unit test:fast, runs in isolation,easy to read, uses real datafailing tests the test
3 Write just enough code to pass itfake implementation, inelegant wayonly pass the test, refactor later
4 Refactor and Test againcode smell?make the bar green
TDD 8 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Steps of TDD
1 Identify missing functionalityrequires analysis of specificationsplits the problem into smaller pieces
2 Write a failing unit testguarantees code to be testedgood unit test:fast, runs in isolation,easy to read, uses real datafailing tests the test
3 Write just enough code to pass itfake implementation, inelegant wayonly pass the test, refactor later
4 Refactor and Test againcode smell?make the bar green
TDD 8 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Steps of TDD
1 Identify missing functionalityrequires analysis of specificationsplits the problem into smaller pieces
2 Write a failing unit testguarantees code to be testedgood unit test:fast, runs in isolation,easy to read, uses real datafailing tests the test
3 Write just enough code to pass itfake implementation, inelegant wayonly pass the test, refactor later
4 Refactor and Test againcode smell?make the bar green
TDD 8 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Steps of TDD
1 Identify missing functionalityrequires analysis of specificationsplits the problem into smaller pieces
2 Write a failing unit testguarantees code to be testedgood unit test:fast, runs in isolation,easy to read, uses real datafailing tests the test
3 Write just enough code to pass itfake implementation, inelegant wayonly pass the test, refactor later
4 Refactor and Test againcode smell?make the bar green
TDD 8 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Coding Example
Steps of TDD
1 Identify missing functionality
2 Write a failing unit test
3 Write just enough code to pass it
4 Refactor andTest again
Settlers of Aachen
The class SoA simulates aboard game. Each playercan register his name.
Task
Implement the functionstart().It returns a String namingthe player and telling him,that his turn has begun.
TDD 9 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Code Smells
duplicated code
long methods, classes
complex branches
obscure code
design patternapplicable?
public class q{
static String s="public class q{1}static String s=
{3}{0}{3}; public static void main(String[] a){1}
System.out.println(java.text.MessageFormat.format(
s,s,’’{1}’’,’’{2}’’,’’{3}’’));{2}{2}";
public static void main(String[] a){
System.out.println(java.text.MessageFormat.format(
s,s,’{’,’}’,’"’));
}
}
TDD 10 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Factory
problem of testing:initialize too many classes
solution: introduce factory
public class SoA_Factory{
SoA getNewSoA() {
SoA soa = new SoA();
Player p1 = new Player();
soa.add_player(p1.name);
...
ResourceFields rf = new ResourceFields();
rf.add(new Wool());
..
soa.add_fields(rf);
return soa;
}
}
TDD 11 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Factory
problem of testing:initialize too many classes
solution: introduce factory
public class SoA_Factory{
SoA getNewSoA() {
SoA soa = new SoA();
Player p1 = new Player();
soa.add_player(p1.name);
...
ResourceFields rf = new ResourceFields();
rf.add(new Wool());
..
soa.add_fields(rf);
return soa;
}
}
TDD 11 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Strategy Pattern
test may interact with complexobjects
non-deterministic behavior(camera data, dice)
slow access (database)
critical execution(paypal.sendAllMyMoney(),nuclearMissile.launch())
solution: Strategy Pattern
extract interface
real object implements theinterface
fake object implements theinterface
public interface IDice {
int roll();
}
public class Dice implements IDice {
public int roll() {
return new Random().nextInt(6) + 1;
}
}
public class CheatDice implements IDice {
public int roll() {
return 6; // chosen by fair dice roll.
// guaranteed to be random.
}
}
TDD 12 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Strategy Pattern
test may interact with complexobjects
non-deterministic behavior(camera data, dice)
slow access (database)
critical execution(paypal.sendAllMyMoney(),nuclearMissile.launch())
solution: Strategy Pattern
extract interface
real object implements theinterface
fake object implements theinterface
public interface IDice {
int roll();
}
public class Dice implements IDice {
public int roll() {
return new Random().nextInt(6) + 1;
}
}
public class CheatDice implements IDice {
public int roll() {
return 6; // chosen by fair dice roll.
// guaranteed to be random.
}
}
TDD 12 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Strategy Pattern
test may interact with complexobjects
non-deterministic behavior(camera data, dice)
slow access (database)
critical execution(paypal.sendAllMyMoney(),nuclearMissile.launch())
solution: Strategy Pattern
extract interface
real object implements theinterface
fake object implements theinterface
public interface IDice {
int roll();
}
public class Dice implements IDice {
public int roll() {
return new Random().nextInt(6) + 1;
}
}
public class CheatDice implements IDice {
public int roll() {
return 6; // chosen by fair dice roll.
// guaranteed to be random.
}
}
TDD 12 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Mock Object
Problem: too many different fake implementations
solution: simulate Interface by Mock Objectpublic void test_rollForResources() {
IDice mockDice = EasyMock.createMock(IDice.class);
EasyMock.expect(mockDice.roll()).andReturn(4);
EasyMock.expect(mockDice.roll()).andReturn(3);
EasyMock.replay(mockDice);
SoA soa = new SoA();
soa.dice = mockDice;
assert (soa.rollForResources() == 7); // this function sums two dice rolls
}
TDD 13 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Mock Object
Problem: too many different fake implementations
solution: simulate Interface by Mock Objectpublic void test_rollForResources() {
IDice mockDice = EasyMock.createMock(IDice.class);
EasyMock.expect(mockDice.roll()).andReturn(4);
EasyMock.expect(mockDice.roll()).andReturn(3);
EasyMock.replay(mockDice);
SoA soa = new SoA();
soa.dice = mockDice;
assert (soa.rollForResources() == 7); // this function sums two dice rolls
}
TDD 13 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Steps of TDD - Summary
TDD 14 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
1 Motivation
2 Test Driven Development
3 Analysis
4 Conclusion
TDD 15 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Better Code Testing
high coverage: cover every line of code
defects early found (every effort worth it)
more confidence, buttests cannot prove the absence of errors,false sense of security
tester = programmer, same blind spotindependent testing still necessary
TDD 16 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Requirements and Documentation
tests define requirements:early requirement analysis(increases confidence)concern early about interface
tests = documentationTDD is specification, not validation
more tests than code
TDD 17 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Clean Code
test guides the implementation
modularized, highly cohesive, loosely coupled code
write functions only if needed (YAGNI)
encourages simple designs, inspires confidence
TDD 18 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Scalability
test-runs take time
split into test-suite hierarchy
maintenance overhead, more code
problem if many tests fail simultaneouslye.g. due to elementary design change
TDD 19 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
1 Motivation
2 Test Driven Development
3 Analysis
4 Conclusion
TDD 20 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Studies
how to measure software quality?defect density?
TDD 21 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Literature
David S. Janzen and Hossein Saiedian.Test-Driven Development: Concepts, Taxonomy,andFuture Direction.http://works.bepress.com/djanzen/6
Kent Beck.Test-Driven Development by Example(Addison-Wesley Signature)
Dan Pilone, Russ Miles.Head First Software Development
http://www.agiledata.org/essays/tdd.html
Prof. Lichter.lecture Software Quality Assurance,2012 RWTH
Mark Dowson.The Ariane 5 Software Failure.SIGSOFT Software Engineering Notes,March 1997
TDD 22 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Images
Ariane 5
www.capcomespace.net/dossiers/espace_europeen/ariane/ariane5/AR501/V88_AR501.htm
Money, Time, Quality
www.brucesallan.com/wp-content/uploads/2012/05/ROIdice1.jpg
Kiss
dryinkdesigns.files.wordpress.com/2012/06/062112_kiss.png
Settlers of Catan
www.catan.com
SmellfishProf. Lichter. lecture Software Quality Assurance, 2012 RWTH
Drawing Hands,by M. C. Escher, 1948, Lithograph
Factory
www.clipartheaven.com
Cheat Dice
http://www.slidetoplay.com/game/cheat-dice
Documentation
www.picospin.com/wp-content/uploads/2011/12/documentation1.jpg
TDD 23 A. Helligrath
Motivation Test Driven Development Analysis Conclusion
Summary
TDD 24 A. Helligrath
![Data-Driven and Keyword-Driven Test[1]](https://static.fdocuments.in/doc/165x107/577ce76d1a28abf103951d8d/data-driven-and-keyword-driven-test1.jpg)
