taming the monster legacy code beast
Post on 10-May-2015
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Taming Legacy Code Monsters
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Caleb *
* I’m here to help.
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10 Reasons your software Sucks(and the 10 practices to fix it)
Last year
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DevelopmentObject Orientation
SOLID
Patterns
Secure Coding
Team WorkAutomated Tests
Source Control
Automated Builds
ProcessAgile, Lean, XP
Team Dynamics
Continuous Learning
Bui ld ing teams that engineer better software
Development ∙ Team Work ∙ Process
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back to…
Taming Legacy Code Monsters
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back to…
Taming Legacy Code Monsters
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Definition “Legacy”n. Software that I’m afraid to maintain,
extend, or change it actually scares me to
touch that code.
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What’s the difference between an application and
UI Auth Validation
Rules Workflow Processor
Services Data Cache
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Legacy Monster
UI Auth Validation
Rules Workflow Processor
Services Data Cache
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Legacy MonsterStatic ConfigStatic ProxyProcessor SettingsData ConnectionsRules Configurations
Rules
Processor
Data
Coupling
Cou
plin
g
Coupling
Coupling
CouplingCoupling
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Legacy MonsterSolution contained over 68 projects.
Most of which were not used.
No horizontal layers.
Required IIS 6 / legacy URL rewriter / 32 bit C Lib / IIS Rules export/import /
Database Connections / Proper Configuration X 3
To run or test ANY part on a dev box…
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Know your FoeStra
tegy #1
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nDepend
Strategy #1
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Visual Studio Dependency Graph
Strategy #1
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Strategy #1
DemoUsing theVisual Studio Dependency Graph
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Pro tip:Look for big blobs & thick lines to concrete types
Strategy #1
Demo
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Strategy #2
Create a
Safety Net
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Strategy #2
Source Control+ Test
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Strategy #2
Source Control+ Test
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Strategy #2
Source Control
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// source// trunk
// r1 // r2 // r3
// r1.1
// trunk
//
// svn / git / tfs ..
Branching for FUN!
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Strategy #2
Tests
Unit TestsIntegrationRegressionLoad TestsEtc…
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Isolation and White box Unit Testing for .NET
Legacy MonsterStatic ConfigStatic IProxyProcessor SettingsData ConnectionsRules Configurations
Rules
Processor
Data
“Pex automatically generates test suites with high code coverage. …[and] finds interesting input-output values of your methods, which you can save as a small test suite with high code coverage. Microsoft Pex is a Visual Studio add-in for testing .NET Framework applications.”
http://research.microsoft.com/en-us/projects/pex/
Demo: Safety Net
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what about hard to test code?refactoring testability
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private IList<Bean> goodBeans { get; set;}private IList<Bean> badBeans { get; set;}
public void AddBean(Bean bean){
if (bean.size > 10)goodBeans.Add(bean);
elsebadBeans.Add(bean);
}public void UpdateBeans(){ BeanData.Update(goodBeans); goodBeans.Clear(); badBeans.Clear();}
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Clearly an arbitrary example1Does represent actual production code that I have worked with
Usage scenario is2AddBean(b); AddBean(b), UpdateBeans();
How can we test the AddBean() Logic?3
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private IList<Bean> goodBeans { get; set;}private IList<Bean> badBeans { get; set;}
public void AddBean(Bean bean){
if (bean.size > 10)goodBeans.Add(bean);
elsebadBeans.Add(bean);
}public void UpdateBeans(){ BeanData.Update(goodBeans); goodBeans.Clear(); badBeans.Clear();}
public IList<Bean> GoodBeans { get; private set;}private Ilist <Bean>badBeans { get; set;}
public void AddBean(Bean bean){
if (bean.size > 10)GoodBeans.Add(bean);
elsebadBeans.Add(bean);
}public void UpdateBeans(){ BeanData.Update(goodBeans); GoodBeans.Clear(); badBeans.Clear();}
A: create a readonlyaccessor to “sense” thegoodBean state externally
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public void UpdateBeans(){ BeanData.Update(goodBeans);
goodBeans.Clear(); badBeans.Clear();
}
What about the UpdateBeans() method?public void UpdateBeans(){ BeanData.Update(goodBeans);
goodBeans.Clear(); badBeans.Clear();
if (OnBeansUpdate != null) OnBeansUpdate();}
public event Action OnBeansUpdate;
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Not a silver bullet
still need to make sure that we are testing “the right” things, and not just hitting some magical number
still need to make sure we have healthy tests
Code Coverage + Continuous Integration
Pro tip
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Code Coverage + Continuous IntegrationCreates a base line or smoke test to look for
Watch trends over magic percent numbers
Pro tip
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Code Coverage + Continuous IntegrationTeam City Code Coverage
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Code Coverage + Continuous IntegrationSonar
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Strategy #3
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Strategy #3
Divide and Conquer
(pick your battles)
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Commitment
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Commitment Raise your hand and repeat after me,
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Commitment Raise your hand and repeat after me,
I will not practice bad code.
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“Resist Legacy Coupling”
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“Resist Legacy Coupling”Legacy Monster
Static ConfigStatic ProxyProcessor SettingsData ConnectionsRules Configurations
Rules
Processor
Data
Coupling
Cou
plin
g
CouplingC
oupling CouplingCoupling
tight coupling = change anywhereaffects everything
New Functionality
Needs IProxy
don’t reference Config Monster
use DI for only what you need (IProxy)
static Config class leads to Heavy Weight testing
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Introduce SOLID principals on new development… gradually improve code over time
http://developingux.com/di/
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wrap up
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wrap upKnow your Foe
Use a Safety Net
Divide and Conquer
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@calebjenkins
@proactionmentor
http://developingux.com
caleb@proactionmentors.com
Thank you!
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Photo Credits
http://www.flickr.com/photos/boogeyman13/2432667459/
http://www.flickr.com/photos/stopthegears/50553611/
http://www.flickr.com/photos/pochateca/324414459
http://www.flickr.com/photos/27620885@N02/2594362917
© Michael Cummings - http://dreaminpictures.com
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http://www.flickr.com/photos/flyingturtle/3976070342/
http://www.lostechies.com/blogs/derickbailey/archive/2009/02/11/solid-development-principles-in-motivational-pictures.aspx
http://www.flickr.com/photos/jfravel/1001472806/
http://www.flickr.com/photos/flyingturtle/3976076272/
http://www.flickr.com/photos/27620885@N02/2594363003
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