Testing

Steve LoughranHP LaboratoriesJune 9th, 2008

About me* I break things for a

living* this is because I am

clumsy* breaking other people’s

code is fun* sometimes it is really

hard

Ant in Action* the problems of complex

builds in big teams* not for this course* stay in the IDE* testing is key to getting

big projects out the door* automation comes next

your code doesn't work

I know this because...

my code doesn't work

it's OK to write code that doesn’t work

but not to ship it

especially when it matters

how do you get from "broken" to "shipping"?

Device Drivers

ship and see

test it!

Test-Driven

x: y : f(y, x)>0

Formal Methods

prove it works

proofs of correctness

+shows an algorithm really works+good for concurrency+and other things you can’t test

- makes assumptions about system- needs lots of maths/CS skills

(Pi-Calculus, The HOL System)- how do you do regression proofs?

Testing: code that breaks

* unit test: test classes, libraries* functional test: test the application* system test: test a deployed system* performance test: simulate load.* acceptance tests: is it ready for use?

a good test breaks the build!

Test Driven Development

any feature without a test doesn’t exist

Lots of unit test frameworks

* Java: JUnit, TestNG* Python: PyUnit* Ruby: Test::Unit * .NET: NUnit* PHP: PHPUnit* C++ (CppUnit)

JUnit

* main unit test framework in Java (see also TestNG)

* simple to learn* good tool support* somewhat low-level* extensions for system testing

+count Test Cases( )+r un( )

«i nt er f ace»Test

+asser t Tr ue( )+asser t Fal se( )+f ai l ( )+asser t Equal s( )+asser t Same( )+asser t Not Same( )+asser t Nul l ( )+asser t Not Nul l ( )

Assert

+set Up( )+t earDown( )

TestCaseTestSui te

1

*

public class LessSimpleTest extends TestCase {

public LessSimpleTest(String s) { super(s); }

public void testAssignment() { final Date date = new Date(); Event event = new Event(UUID.randomUUID(),

date, "now", "Text"); assertEquals("self equality failed", event, event); assertEquals(date, event.getDate()); assertNotNull(date.getID()); }}

swing GUI TestRunner

Ant-generated report

scales better; reports published

Continuous Integration

see: CruiseControl, Hudson, LuntBuild

==> blame assignment

whose change broke the build?

System Testing

* deploy, then:HtmlUnit, XmlUnit, Cactus, Selenium

* needs automated deployment, database setup, teardown

* performance testing by comparing timings w.r.t. old runs

* simulate entire behaviour of the client user/application

Distributed Systems

testing is still a research topic

* set up complex configurations* run tests on remote machines* collect results and log data* post-mortem analysis* virtualization can help

see http://tinyurl.com/y99tez

limitations of testing

- good tests are hard to write- distributed tests very hard- different system configurations are still a

problem- status of "tester" below "coder"

A good test breaks the application

politics:resistance to change

developers: ignorance, fear

E.E.E. Educate, Evangelise, Encourage

* gently show benefits* use testing to track down a bug* retain test for regression testing* add tests for new code and old problems, not

existing codebase* adopt cruise control, reporting

management: ignorance

"too much time spent on testing"

* out of date with modern processes* belief that testing slows the schedule (it does

on the ship-and-see process)

E.E.E., then D.D.D: Distract, Dissemble, Defeat

call to action

* write tests* use a CI tool: Hudson,

Luntbuild,Cruise Control