Transcript The Road To Test-Driven Development By Christopher Paulicka Software Engineering Manager Copyright Oversee.net 2008 11/6/2015

The Road To Test-Driven
Development
By Christopher Paulicka
Software Engineering Manager
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Introduction
Not just what Test-Driven Development
is…
 But also how to get to Test-Driven
Development

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Agenda
What is Test-Driven Development
 One (Abstract) Road to Test-Driven
Development
 Your Road to Test-Driven Development
 My Road to Test-Driven Development

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Vocabulary
Test-Driven Development – TDD
 Extreme Programming - XP

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Thanks

Perl Mongers for showing up!
Oversee.net for the nice space
 Michael Lee, Director of Engineering, for
“volunteering” me
 All the development team here at Oversee
for feedback

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The Three Participants
Christopher Paulicka
 Oversee.net
 Perl Mongers

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Christopher Paulicka
Software Development – 16 years
 Testing – 10 years
 Perl – 4 years
 Test-Driven Development – 1 year

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Oversee Development
Environment
Agile/Scrum
 Perforce
 Linux/Apache/MySQL/Perl, RPM
 Mason/Catalyst, DBI
 Test::More, Test::MockObject
 Test::Unit, Test::WWW::Selenium
 Module::Build, CPAN2RPM

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Perl Mongers
Perl aficionados
 Please ask questions at any time
 What’s your testing experience?

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What is TDD
TDD is old, but kind of new
 Test first, but still follow requirements
 Part of Agile/XP, but reusable anywhere

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Important to Know
History of TDD in Extreme Programming
 History of Scrum at Oversee

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Software Development
Methodologies
Hack
 Waterfall
 Agile

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Waterfall Development
Requirements
 Design
 Implement
 Test
 Maintain

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Waterfall Costs
Rigid design
 High change costs
 Requires expert designers up front

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Examples of Agile
Methodologies
Extreme Programming
 Scrum
 Crystal Clear
 Feature Driven Development
 Adaptive Software Development
 DSDM

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Extreme Programming
Test-Driven Development
 Continuous Integration
 Pair Programming
 Refactoring

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Cost of Feedback
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Test-Driven Development
Pick a Feature
 Write a Test for that Feature
 Run all Tests and see new Test Fail
 Write Code for Feature
 Run all Tests and see all Tests Pass
 Refactor
 Repeat
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A Bit More About Refactoring
Refactor the Code
 Refactor the Tests
 Refactor the Documentation
 Refactor the Design

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Who owns testing?
QA
 Deploy
 Systems
 Development

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Types of Testing
Requirements Tests
 Integration Tests
 System Tests
 Development Tests
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Types of Development Testing
Unit Tests
 Regression Tests

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One Possible Road to TDD
Test to Verify
 Test for Regression
 Test for Design
 Test-Driven Development

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Test To Verify
Problem arises
 Write throw away test
 Disposable code modifications

– Logging
– Dumping, etc
Simple and Fast
 Gone forever…

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Why Do We Do That?
Habit
 Speed
 Anticipation (almost done…)

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Test for Regression
Problem arises
 Write reusable test that duplicates problem
 Keep regression test
 Run regressions anytime

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Good, but Good enough?
Bug driven
 Prevents regressions
 Run tests anytime in development
 Focused late in the curve
 Expects test framework

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Test for Design
Design API
 Write Code
 Write Tests
 Refactor

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Development Test Processes
Piece-wise Test Last
 Lump-sum Test Last
 Test First aka TDD

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Test-Driven Development

As Beck said in XP
– Good Rules, lead to
– Good Behavior, which give
– Good Unit Tests
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Rules
Write code only when test fails
 Eliminate duplication afterwards

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Behaviors
Organic Design
 Writing own tests
 Rapid response
 Modular Design

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Good Unit Tests
Run fast
 Run in isolation
 Easy to understand
 Use real data
 Incremental step (not too large)

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Your Road To TDD
Why TDD
 Cost/Benefit Analysis
 How To Start

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Why Test Driven Design
Tests as Use Cases
 Tests as Documentation
 Tests as Design
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Possible reasons to avoid TDD
Tests are programmer focused
 May not be requirement focused
 Running all tests are slow
 Sprinting
 Refactoring
 Comparing
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Cost/Benefit of TDD
Industry Analysis
 Personal Analysis

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Benefits - Industry Analysis
Reduce development lead-time
significantly
 Programmers that write tests are more
productive
 Rarely use a debugger
 Easy to revert on test failure
…

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Benefits – Industry Analysis (cont)
Programmers tests interface first, then
code
 Shorter implementation time
 High Code coverage
 Regressions
 More modular code

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Costs – Industry Analysis

More code
– Though higher productivity with TDD

Costly test setup
– UI
– DB
– Multithreaded

Large legacy code bases
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Metrics – Industry Analysis
TDD code passed 18 - 50% more external
test cases than control group code
 TDD code had 10 – 50% less time spent
debugging code
 TDD had from 0 - 16% decrease in
productivity (in lines of non-test code)
…

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Metrics – Industry Analysis (cont)
TDD has 163% more asserts/module
 TDD 2-3x higher test coverage

– line and condition coverage near 100%

TDD coders spent 13% less time
producing solutions that were 12% larger
then control (including tests!)
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Subjective – Industry Analysis
After the study, when asked:
 TDD would stick with TDD
 TLD would go to TDD (60%+)
 No tests would go to TLD
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Benefits – Personal Analysis

Senior/Junior Developer Interaction
– Senior approve tests/API
– Junior implements API
– Senior code reviews, done
Tests as Use Cases
 Test Documentation more stable then Code
Documentation

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Costs – Personal Analysis

More code
– Though happier with more feedback

Costly test setup
– UI - WWW::Mechanize
– DB – Test::MockObject
– Multithreaded - …heh…yes.

Large Legacy Codebases are painful, but
TDD may be very beneficial…it’s a start!
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How To Start
Believe in Testing
 Test Framework
 Test Coverage
 Write Tests First

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Believe in Testing
If it's worth building, it's worth testing.
 If it's not worth testing, why are you
wasting your time working on it?

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Test Frameworks
Perl has a lot…
 Test::Simple
 Test::More
 Test::Unit
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Test Coverage
Provide metrics
 Devel::Cover

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Write Tests First
Code review tests
 Pair program tests
 Always ask, “Where’s the test?”
 Help make tests easier

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Be Aware!
You are now becoming a test expert!
 TDD Antipatterns
 Don’t test just to test…

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My Road To Test-Driven
Development
Hewlett-Packard EMSO
 Idealab

– X1
– Energy Innovations
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Lessons from Hewlett-Packard
Tests are nowhere near perfect
 Tests can prove your point
 Believe in tests!

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Tests are nowhere near perfect
500000 lines of code
 Hundreds of feature tests working
 Applications run for 3 days
 I knew it was broken

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Tests can prove your point
No one wanted to believe it
 The product needed to ship
 Wrote random component
creator/messenger/destroyer
 Core dump in less then a millisecond
 Created tests from random iterations
 Fixed hundreds of memory leaks and
contention issues

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Lessons from X1
Good Test Framework
 Keep each other honest

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Good Test Framework
Test::Unit
 WWW::Mechanize
 DBI

– No MockObjects
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Keep each other honest
Test First, not test eventually
 Everybody Writes Tests…
 …but feel free to ask for help

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Lessons from Energy
Innovations
Cost of Refactoring
 Beware Gold Plating
 It’s easy to get lazy…

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Summary
Learned about TDD
 Learned about benefits (and costs) of TDD
 Learned first steps towards TDD

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Q&A
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Bibliography

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I would highly recommend “The Object Primer”
by Scott W. Ambler, now in it’s third edition.
http://www.agiledata.org/essays/tdd.html
http://en.wikipedia.org/wiki/Testdriven_development
http://en.wikipedia.org/wiki/Agile_software_dev
elopment
http://en.wikipedia.org/wiki/Continuous_integrati
on
http://en.wikipedia.org/wiki/Refactoring
…
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Bibliography (cont)
 http://blog.james-carr.org/?p=44
http://www.ipd.uka.de/Tichy/uploads/publi
kationen/136/MuellerHoefer2007.pdf
 http://www.acm.org/src/subpages/gf_entrie
s_06/DavidJanzen_src_gf06.pdf
 http://utopia.csis.pace.edu/dps/2008/mcape
llan/projects/TDD/TDD_Idea_Paper_V0403.doc
…

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Bibliography (cont)
http://www.sciencedirect.com/science?_ob
=ArticleURL&_udi=B75H1-4FC40MJ2&_user=10&_rdoc=1&_fmt=&_orig=sea
rch&_sort=d&view=c&_acct=C00005022
1&_version=1&_urlVersion=0&_userid=1
0&md5=fbd92b394263506930dfafb31003
a916
 http://aegis.sourceforge.net/

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