Software Testing JUnit Testing - Team Project 2016mmk/teaching/tp/09-Junit.pdf · Software Testing { JUnit Testing Team Project 2016 Presented by Manfred Kerber slides adapted from

Software Testing – JUnit TestingTeam Project 2016

Presented by Manfred Kerberslides adapted from slides by Christoph Lange

(reusing material from Chris Bowers)

Version: 22 January 2016

1 / 29 c©Manfred Kerber, 2016

Testing Methods

White box

Test the code explicitly, “from within”Cover all possible paths of execution“Does this method do what I intended?”

Black box

Independent of code, “like an outsider”Specification based“Does this software fulfil my requirements?”

Both can be automated


Purpose of black-box testing

User testing

UsabilityUser experienceUser acceptance testing

Security

Ethical hacking – penetration testsIdentify vulnerabilities

Performance

Load, stress testing becomes soak testing


Purpose of white-box testing

“Defensive programming”

Test all paths through the code

e.g. both branches of an if-then-elseTools exist to check test coverage


Test-driven development (1)

A programmer has to be able to demonstrate that his programhas the required properties. If this comes as an afterthought, it isall but certain that he won’t be able to meet this obligation onlyif he allows this obligation to influence his design, there is hopethat he can meet it. Pure a posteriori verification denies you thatwholesome influence and is therefore putting the cart before thehorse ... –E. W. Dijkstra (2000)

You don’t write code with its purpose as an afterthought. You thinkabout it first. Right?

But ... the “purpose” can change frequently.

Need a formal, precise and verifiable way to define purpose.



Program by intent1 Start by defining a set of test cases

Pay attention to border cases!

2 Write code that passes the tests

public class TestWordStemmer {

public void testStemmer() {

WordStemmer stemmer = new WordStemmer ();

assert stemmer.stem("helping") == "help";

assert stemmer.stem("hungrily") == "hungry";

assert stemmer.stem("friendliness") == "friend";

assert stemmer.stem("play") == "play";

assert stemmer.stem("playing") == "play";

assert stemmer.stem("player") == "play";

// ...

}

}



Use tests as a template to create code

public class WordStemmer {

public String stem(String word) {

String stemmed_word;

// do stemming

return stemmed_word;

}

}




Design patterns

Abstraction of approach to solving common problems

Can define:

High level strategySoftware architectureWork flow (events)

Finding the right pattern can make defining test cases easier


Unit testing

Unit – small functional part of application that can be testedindependently

A unit could be an individual class or method

A set of test cases are constructed to form a test harness


JUnit testing with Eclipse

JUnit: unit testing library for Java

Integrated into NetBeans/Eclipse/XCode/... IDEs

Separates source code from testing code

IDEs provide lots of nifty inspection tools

Well documented


Live Eclipse example (1)

Outline:

1 creating JUnit test

2 writing test cases3 coding by intent

1 getting it wrong ⇒ test fails2 getting it right ⇒ test passes


Live Eclipse example (2): Creating JUnit test










Live Eclipse example (7): Writing test cases


Live Eclipse example (8): Running a test


Live Eclipse example (9): Running a test


Live Eclipse example (10): Test-driven development








JUnit assertions

Statement What it does

fail() Lets the test fail. Useful for checking codeis not reached under certain conditions.

assertTrue(boolCond) Checks that a condition is trueassertEquals(expected, Checks that two values are the same. Not a deepactual, [tolerance]) check, i.e., be careful with non-primitive values.assertNull(object) Check that an object is nullassertNotNull(object) Check that an object is not nullassertSame(expected, Check that both object references are the same.actual)assertNotSame(expected, Check that both object references are not the same.actual)

All methods take an optional first argument message.

Tolerance is for floating point numbers.


JUnit annotations

Statement What it does

@Test Marks a test method@Test(timeout=1000) Test fails if timeout (in ms) exceeded@Test(expException) Test fails if defined exception is not thrown@Before @After Code that should be executed before or

after every test@BeforeClass @AfterClass One-off setup/teardown code (e.g.

database login)@Ignore Ignore this test

Usage:

@Test(timeout=1000)

public void underOneSecond() {}


JUnit can’t test everything

Input/output is hard to test

need to maintain separate test filesor prepare strings/arrays that simulate file contents (if code to betested supports streams)

GUIs are even harder to test

separation of GUI and underlying logic helps (e.g. model-view-controllerdesign pattern)JUnit extensions (e.g. Abbot) facilitate GUI testing


Just getting you started

Some useful resources:

JUnit homepage

http://junit.org

2-page summary (includes Eclipse basics)

https://www.cs.bham.ac.uk/internal/courses/java/msc/resources/junit-

basics.pdf

NetBeans JUnit tutorialhttp://netbeans.org/kb/docs/java/junit-intro.html

Eclipse JUnit tutorial

http://www.vogella.com/articles/JUnit/article.html


http://junit.org

https://www.cs.bham.ac.uk/internal/courses/java/msc/resources/junit-basics.pdf

https://www.cs.bham.ac.uk/internal/courses/java/msc/resources/junit-basics.pdf

http://netbeans.org/kb/docs/java/junit-intro.html

http://www.vogella.com/articles/JUnit/article.html

Final comments

Four take home points:

Keep it simple, Stupid!

Design by contract.

Use design patterns.

Write beautiful code.


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Software Testing JUnit Testing - Team Project 2016mmk/teaching/tp/09-Junit.pdf · Software Testing { JUnit Testing Team Project 2016 Presented by Manfred Kerber slides adapted from