Testing: the more you do it, the more you'll like it

Testen: Je mehr Du es tust,
desto mehr wirst Du es lieben
“I can’t believe we’re still talking about this!”

Testen: Je mehr Du es liebst,
desto mehr wirst Du es tun
“I can’t believe we’re still talking about this!”

Sebastian Bergmann
@s_bergmann
sebastian@thephp.cc
27 years programming experience
19 years PHP experience
Co-Founder of thePHP.cc

Jeffrey A. "jam" McGuire
Evangelist, DevRel Acquia
dev.acquia.com/podcast
@horncologne
jam@acquia.com
horncologne@gmail.com

Acquia Podcast:
dev.acquia.com/podcast

Introduction
Why testing? What’s the problem?
Benefits of testing.
Addressing roadblocks and
objections to testing.
Result!
Outline

Why testing?
“The software team not only has to ensure that it makes a
positive contribution to the business goals; it must also ensure
that it makes as few negative contributions … as possible.” -
Andresen.

Benefits of testing
(business cases)
“Testing solves many problems, the least of which is being
sure the code does what it is supposed to do.”

The Phoenix Project: A Novel About
IT, DevOps, and Helping Your
Business Win
Gene Kim, Kevin Behr, George
Spafford
https://en.wikipedia.org/wiki/
The_Phoenix_Project_(novel)

The Four Types of Work
1. Business project
2. IT (Infrastructure/Internal) project
3. Changes (Operational/Maintenance)
4. Unplanned work

TDD & the Four Types of Work
TDD helps focus on delivering
features/value through business and
IT projects.
TDD makes changes (Operational/
Maintenance) faster, more secure
TDD reduces unplanned work

Time out!
State-of-play?
Do you even test?

I find your lack of tests disturbing.

http://dl.acm.org/citation.cfm?id=952753
SAC '03 Proceedings of the 2003 ACM
symposium on Applied computing
Pages 1135-1139
ACM New York, NY, USA ©2003
ISBN:1-58113-624-2
1

ISESE '06 Proceedings of the 2006 ACM/IEEE
international symposium on Empirical software
engineering, Pages 356-363
ACM New York, NY, USA ©2006
ISBN:1-59593-218-6
2

IEEE Transactions on Software Engineering
Volume 31 Issue 3, March 2005
Page 226-237
3

ISSRE'09 Proceedings of the 20th IEEE
international conference on software reliability
engineering, Pages 81-89
IEEE Press Piscataway, NJ, USA ©2009
ISBN: 978-1-4244-5375-7
4

ICSE '03 Proceedings of the 25th International
Conference on Software Engineering,
Pages 564-569, IEEE Computer Society
Washington, DC, USA ©2003
ISBN:0-7695-1877-X
5

Pro
1. 18% more functional tests passed
2. More than 2X increase in code quality, 
tests served as “auto documentation”
3. more tests == more productivity 
more productivity == better quality
4. 20.9% decrease in defects, 
decrease in defects found by customers 
5. 50% reduction in defect rate, 
the test suite “will improve quality over
lifetime of the software system”, “quality
contract” between team members
6. TDD ROI … Show me the money!
Con
1. 16% more development time
2. 15% more development time 
3. - 
4. 30% more development time 
non-iterative testing (improvement
possible)
5. (“minimal development productivity
impact”) 
 
6. - 
 
Summary

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.7.4232
About the Return on Investment of Test-Driven Development (2003)
Matthias M. Müller , Frank Padberg
International Workshop on Economics-Driven Software Engineering
Research EDSER-5
6

Conventional
TDD
Development Quality Assurance
Development
Investment
Life Cycle Benefit
Net Return
Müller / Radberg - TDD Benefit/Cost Ratio Calculation

“In most cases, a client will not
state how long a comparable
previous system functioned …
Request this information and use it
in relation to test-driven
development.” - Andresen.
Photo by CEphoto, Uwe Aranas

Developers!
This book is your friend!
https://leanpub.com/
SellingTestDrivenProjects

Boehm - Relative cost of a bug-fix
0
40
80
120
160 150X
50X
20X
10X5X1X
Requirements Design Code Developer
Tests
Acceptance
Tests
Operations

Delivering the project
is only the beginning
of delivering value.
“Many software teams present quality assurance as a
separate item in their offer … This gives clients the impression
that it is an element that can be eliminated.” - Andresen.

Roadblocks,
Questions,
Objections
Getting to testing

Objections &
Questions
1. What can developers get out
testing?
2. How does testing save time and
frustration?
3. But I’m writing the software twice!
That’s twice as much work!
4. What’s the most important tip you
can give about testing?

“Die Hauptaufgabe eines Entwicklers
ist nicht das Schreiben von Code,
sondern das Verstehen eines
Problems. Das Formulieren von Tests,
also der Zielvorgaben, hilft, ein
Problem Schritt für Schritt zu
durchdringen. Die Tests treiben die
Entwicklung also nicht als
Selbstzweck, sondern tun dies, indem
sie die notwendigen Denkprozesse
anstoßen.”
https://thephp.cc/neuigkeiten/2017/02/testen-haelt-mich-von-der-arbeit-ab

class AuctionTest extends PHPUnitFrameworkTestCase
{
private $auction;
protected function setUp()
{
$this->auction = new Auction(
new User(
new Name('Tess Tester'),
new Email('tester@example.com')
),
new Description('...'),
new DateTimeImmutable('2017-04-07'),
new DateTimeImmutable('2017-04-15'),
EUR::fromCents(100)
);
}
// ...
}

class AuctionTest extends PHPUnitFrameworkTestCase
{
// ...
public function testUserCannotBidOnOwnAuction()
{
$this->expectException(
CannotBidOnOwnAuctionException::class
);
$this->auction->bid(
new Bid(
new DateTimeImmutable(‘2017-04-08'),
$this->auction->getUser(),
EUR::fromCents(100)
)
);
}
}

$ phpunit --testdox AuctionTest
PHPUnit 6.0.13 by Sebastian Bergmann and contributors.
Runtime: PHP 7.1.2 with Xdebug 2.5.1
Configuration: /home/sb/example/phpunit.xml
Auction
[x] Has description
[x] Has start date
[x] Has end date
[x] Has initial price
[x] User can bid on auction created by another user
[x] User cannot bid on own auction
[x] User cannot bid on auction that has not yet started
[x] User cannot bid on auction that has already ended

Introduction
Why testing? What’s the problem?
Benefits of testing.
Addressing roadblocks and
objections to testing.
Result!
Recap

Photo Credits
https://creativecommons.org/licenses/by-nc-sa/2.0/:
Sebastian Bergmann https://www.flickr.com/photos/stuartherbert/
6231499431
Locomotive spec https://www.flickr.com/photos/
12567713@N00/281324130
Steam engine https://www.flickr.com/photos/lofink/445470024
Train maintenance https://www.flickr.com/photos/kheelcenter/
5279863818/
Motorcycle rider https://www.flickr.com/photos/conner395/8339912312
https://creativecommons.org/licenses/by-nc-sa/2.0/:
Köln/Bonn Flughafen night https://www.flickr.com/photos/top10-flickr/
8676295874/
Köln/Bonn Flughafen day https://www.flickr.com/photos/
dirkvorderstrasse/10583451894/
Flughafen Köln/Bonn ceiling https://www.flickr.com/photos/
fridgemonkey/4262843982/
—————
Köln Musical Dome photo by CEphoto, Uwe Aranas https://
commons.wikimedia.org/wiki/File:Cologne_Germany_Musical-
Dome-01.jpg

Thank you!
Questions?
Sebastian Bergmann
@s_bergmann

sebastian@thephp.cc

Jeffrey A. "jam" McGuire
@horncologne

jam@acquia.com

horncologne@gmail.com

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