100 % confident with legacy code

100% Confident with Legacy

Code

Johan MARTINSSON

Developer - Independent

[email protected]

@johan_alps

Rémy SANLAVILLE

Developer - Orange Software Expert

[email protected]

@sanlaville

mailto:[email protected]

https://twitter.com/johan_alps

mailto:[email protected]

https://twitter.com/sanlaville

Working with Legacy Code


Refactoring Legacy Code with Object

Calisthenics2012 - 2013

Anonymous Developers - Season 1


100% Confident with Legacy Code

2014


Testing Legacy Code - Blockers

Integration tests are too long

Unit tests are too coupled to the source code

Hard and long to write tests

Testing Legacy Code

100% Confident with Legacy Code

2014


Testing Legacy Code

Don’t forget to replace

temporary refactoring

tests

by maintainable tests

Trivia Challengehttp://www.hasbro.com/games/en_US/shop/details.cfm?R=93C6EE71-

6D40-1014-8BF0-9EFBF894F9D4:en_US

https://github.com/jbrains/trivia

It simulates a trivia game

using a randomizer

for correct and wrong answers

How long do you need to

reach ~100% code coverage ?

http://www.hasbro.com/games/en_US/shop/details.cfm?R=93C6EE71-6D40-1014-8BF0-9EFBF894F9D4:en_US


Trivia Challengehttps://github.com/jbrains/trivia

http://www.hasbro.com/games/en_US/shop/details.cfm?R=93C6EE71-

6D40-1014-8BF0-9EFBF894F9D4:en_US

It works well because there

are no dependencies

1

1

Serialize game state and

compare it with Approval Tests1

Cover all branches by

variying the results of the

randomizer

2

2


http://www.hasbro.com/games/en_US/shop/details.cfm?R=93C6EE71-6D40-1014-8BF0-9EFBF894F9D4:en_US

Server 1Server 2

EncodeAudioLegacy Challenge

Remote Server 1

Audio File encoding

HTTPS Server 2

Audio File Encoded

Audio File

Audio File available

at Remote Server 1

Encoded Audio File

available

download upload

Encode Audio Engine

Baby Steps

Step0: Development environment validation

Step1: String comparison with ApprovalTests

Step2: Branch coverage by input parameter variation

Step3: Serializing a complex type

Step4: Mocking web services

Step5: Capturing side effects

Step 0: Development environment validation

EclEmmaJUnit

Technical Solution: Unit Testing + Code Coverage Tool + Diff

Tool

Context: Launch UT + Code Coverage + String comparison

Server 1

Remote Server 1

Audio Filedownload

Server 2

encoding

HTTPS Server 2


at Remote Server 1

Encode Audio Engineupload

Audio File Encoded

Audio File

Encoded

Audio File

Encoded Audio File

available

Meld

WinMerge…

Step 1: Method returns a primitive type

Technical Solution: Approval Tests (string comparison)

Context: No side effect + Method returns a primitive type

Server 1

Remote Server 1

Audio Filedownload

Server 2

encoding

HTTPS Server 2


at Remote Server 1


Audio File Encoded

Audio File

Encoded

Audio File

Encoded Audio File

available

Note: encoding issues

Step 2: Branches coverage by input

parameters variation

Technical Solution: Approval Tests (legacyApprovals)

Context: No side effect + Method returns a primitive type

Server 2

encoding

HTTPS Server 2


at Remote Server 1


Audio File Encoded

Audio File

Encoded

Audio File

Encoded Audio File

available

Server 1

Remote Server 1

Audio Filedownload

Step 3: Method returns a complex type

Note: date issues

Context: No side effect + Method returns a complex type

Technical Solution: Approval Tests + XStream

Server 1

Remote Server 1

Audio Filedownload

Server 2

encoding

HTTPS Server 2


at Remote Server 1


Audio File Encoded

Audio File

Encoded

Audio File

Encoded Audio File

available

IFluxTmlg

IBodyTmlg

ITravelInfoTmlg

IAudioAnnounceTmlg

Server 2

encoding

HTTPS Server 2


at Remote Server 1


Audio File Encoded

Audio File

Encoded

Audio File

Encoded Audio File

available

Step 4: Third-party services

Context: WebService difficult to configure or/and not

avalaible

Technical Solution: Moco

Server 1

Remote Server 1

Audio Filedownload

Step 5: Capturing side effects

Note: can be used for context with void methods

not mocking side effect

Context: Side effects

Technical Solution: State, Side Effects Serialization + Approval

Tests

Server 1

Remote Server 1

Audio Filedownload

Server 2

encoding

HTTPS Server 2


at Remote Server 1


Audio File Encoded

Audio File

Encoded

Audio File

Encoded Audio File

available

Conclusion - Why it’s working?

Easy assertion: record and replay

Even ugly tests do the job (Temporary tests)

Fast to execute

Available good libraries:

Approval Tests, XStream, Moco…

Tests are resilient to refactoring

Next…

http://approvaltests.sourceforge.net/

http://martinsson-johan.blogspot.fr/

http://github.com/dreamhead/moco

https://github.com/pearlfish/pearlfish-java

UI visual diffing

https://www.youtube.com/watch?v=UMnZiTL0tUc

Working Effectively with Legacy Code – in particular for

creating “seams”


http://martinsson-johan.blogspot.fr/

http://github.com/dreamhead/moco

https://github.com/pearlfish/pearlfish-java

https://www.youtube.com/watch?v=UMnZiTL0tUc


Approval Tests

only needs 2

lines!



Run your test

Diff Tool (by default TortoiseMerge)

Cf. Using Reporters in Approval Tests

http://blog.approvaltests.com/2011/12/using-reporters-in-approval-tests.html





Result of the current test

named received



Result reference

named approved



Approve result

and save file


BACKUP

Server 1Server 2

EncodeAudioLegacy Challenge

Remote Server 1

Audio File encoding

HTTPS Server 2


at Remote Server 1

download


AudioAnnouceTmlg

URL Remote Server 1

format

filename

audioConfigTmp

target audio file extension

target encoding properties

httpConfigTmp

Local Tempory Folder path,

URL Remote HTTPS Server 2

Local Tempory Folder

Audio File Encoded

Audio File

Local HTTP

Server

Encoded

Audio File

Encoded Audio File

availableAudioFile

name

format