Testing in Legacy: From Rags to Riches

About me

{

“First name”: “Taras”,

“Last name”: “Slipets”,

“E-mail”: “taras.slipets@gmail.com”,

“LinkedIn Profile”: “http://www.linkedin.com/

pub/taras-slipets/

48/466/516”,

“Interests”: [

“Software Engineering”,

“Music”

]

}

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About presentation

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I’d like to share our experience

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What does it mean – Legacy system?

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Ask expert

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Legacy system is…

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Just long-term project

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What we’ve received

• 11-years old system SUCCESSFULLY running on production servers

• Written in Java 1.4

• No frameworks usage

• No documentation

• No developers who has worked on it

• Impatient customers

• Pantient management

• other surprises…

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Bus factor

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What we’d like to have?

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What we’d like to have?

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Shiny system with all cutting-edge frameworks

Reduce pain of maintenance and support

What we’d like to have?

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Shiny system with all cutting-edge frameworks

Reduce pain of maintenance and support

So, how we did it?

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Logs, logs, logs

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Domain model – classes level

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Domain model – database level

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Domain model – workflows

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Peer review VERY often

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Before changing code

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We need to ensure it works

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Testing

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Testing levels

• Unit tests

• Integration tests

• System tests

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Unit tests

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Integration tests

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System tests

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Test existing and expected behavior

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System testing (feature testing)

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Application under testing

System tests

Process Process

External world communication

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External world communication - mocks

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External world communication - mocks

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External world communication - mocks

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External world communication - mocks

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System tests automation

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Finally – let’s touch code!

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Top occurring issues

• “do-stuff” methods

• “I’m aware of everything” classes

• “Celebrities” classes/interfaces

• “Magic goes here” blocks without comments

• Just obsolete code

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What to do?

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How about

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Refactoring facilities

• Extract method

• Extract interface

• Parameter object

• Method object

• Replace type-checking code with State/Strategy

• Move method/field

• …

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Unit tests jumps into

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Frameworks

• EasyMock

• Mockito

• PowerMock

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Indication

After initial tests are written, use PowerMock as indicator of bad system design

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What is next?

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Most used in our case

• Template method

• Strategy

• State

• Visitor

• Command

• Chain of Responsibility

• Observer

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And again - logs, logs, logs

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Hey, where are new features?

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Extend functionality AFA it’s possible

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How deep refactoring should be?

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Theory the Godmother

• S.O.L.I.D.

• D.R.Y.

• K.I.S.S.

• …

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In real world

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Now we can add integration tests

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What about build/deployment time?

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Simple rule

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But for us it hurt

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Remedy?

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Remedy

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• Make app self-contained

• Simplify manual installation

Operations are happy

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If it steal hurts - automate deployment

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Complete features list + tests for them

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The winner takes it all

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The dreams come true - build-pipeline!

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A-team!

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Links

• http://www.amazon.com/Working-Effectively-Legacy-Michael-Feathers/dp/0131177052

• http://xpdays.com.ua/archive/xp-days-ukraine-2011/materials/legacy/

• http://xpdays.com.ua/archive/xp-days-ukraine-2012/materials/code-story/

• http://jeeconf.com/archive/materials-2014/legacy-projects/

• http://jeeconf.com/materials/web-application-i-have-always-dreamt-of/

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Thanks for your attention!

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