IOC Containers and Unit Testing

8/14/2019 IOC Containers and Unit Testing.

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IOC Containers and Unittesting.

How they improve TDD &

Architecture


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Purpose to demonstrate and promote theutility of IOC Containers for improvingprimarily unit testing coverage.


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First must show that containerinjection has advantages over

manual injection wrt to loosercoupling in classes.


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Manual Injection - Is ok. Especially if the dependency (helper)is created and destroyed with the class using it.

In ClassA

public var model:Model;.....

public var helper:Helper;private var helperModel:HelperModel = model.helperModel ;.....helper = new Helper();helper.helperModel =

helperModel;

In Helper

public var helperModel:HelperModel

//Constructor

public function Helper(){.....}

We are defining helperModel and then using

this definition to set helperModel on thehelper.


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But it does couple Model andHelperModel In Class A.

With a container we could have the two classes uncoupled(Sothat ClassA has no reference to her HelperModel) and isolated- especially helpful for unit testing. And preventing even tightercoupling!


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Container Injection - no coupling.

In ClassA

public var model:Model;

.....

public var helper:Helper;......helper = new Helper();

In Helper

[Inject]public var helperModel:

HelperModel

//Constructor

public function Helper(){}


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TDD often requires some form of injection in order to buildeffective unit tests. This is due to the fact that in order to run atest on a piece of code, often the dev will need to pass the code adummy or null object or a stub.


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This dummy null or stub objectneeds to be created somewhere and then injected.

We have various options all ofwhich are valid:

1. Use a StubDelegate with the

same interface as theDelegate.

2. Create the stub in thetestcase class.

3. Have Stubs for a class orsuite in a Config class anduse a container.


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Use a StubDelegate with the sameinterface as the Delegate.If using Cairngorm this usually means that the stub is passedacross several classes (by injection) before it's injected into theclass with the method under test.

This means that all those classes need to be created and workcorrectly before we can do tdd for our method.

This also encourages thetraversal injection approach.


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Create the stub in the testcase class.

Better for unit tests as you avoid passing stub data across (not better for

functional tests).

I could instantiate the stub in the testCase, but it may be used again, provideddevs are aware of it and if I put it in a config file it would make otherdevelopers aware of it more easily. Rather than wasting time searching for it.Without a config file once found this stubdata is often copy pasted into

another test case, potentially duplicating errors and bad coding standardsflagged by FlexCPD.With a central repository of useful objects they can refer to in writing latertests.

It's also good OOP to separate object creation from its use.This is the utility of the container and in doing itthis way we encourage dependency injection rather than proceduralprogramming where it applies.


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With a container this becomes...Context (Config Class) Test Case Class

public var stubMetricData:Array;......stubMetricData = createStubMetricData();private function createStubMetricData():Array{

...as before....

return stubMetricDataArray;

}

//Now this can be easily found and reused.

//constructorTestCase ():void{addContext()

}public function setup(){

addContext()}

......[Inject]public var stubMetricData;

private function addContext():void

{var context : Context = ActionScriptContextBuilder.

build(ExampleASConfig); context.createDynamicContext().addObject(this);}


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What's the difference between all thesetests!

SEE!http://www.javaranch.com/journal/200603/EvilUnitTests.html#toofunc


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Containers for Unit Testing

A Container makes it easier to isolate each class by injectingstubs directly into the class.

Classes with method to test.

class A

model

helperModel


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Rather than this which often arises frommanual dependency injection.

hese 'unit tests' are really functional tests the lines represent theependencies.


Classes depended on thatshould be stubbed.

The lines representdependencies like model.helperModel

class A

model

helperModel


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Nothing wrong with a few of themdone by developers.

... This way these are actuallyfunctional tests.


Classes depended on thatshould be stubbed.


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Thirdly class architecture.

vs

We do it this way. Better this way


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With container injection this isstraightforward.

With the componentizedapproach to the PresentationModel pattern, there is a single

hierarchy of view components butno hierarchy of presentationmodels. Each view componenthas a corresponding presentation

model, but these models areindependent of one another.They do need coordination viaa domain model. See links.


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[Bindable]public var model:MyComponentPM;

...

We do it this way, manualinjection (and coupled).


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[Inject][Bindable]public var model:MyComponentPM;

...

Better this way with container injection looser coupling noreference to child componentPM


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Why use containers - Agility!

A Container allows us to be more agile.Starting TD development before a contract is defined andstubDelegate is complete.

By creating smaller stubs that involve only units under test.Our code may need refactoring to ensure this.


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Container - decoupling

The container promotes decoupling which produces betterstructured code.

Links see other document.


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Containers - Isolation

This leads to a focus on true unit testing and less functionaltesting that passes a stub delegate across the Cairngormsequence if there's a problem with the sequence we have aproblem with our method under test, by passing the

dependency manually.


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Containers - Clarity

Config becomes a central repository of stubs for a particulartest case that other developers can easily be made aware ofand peruse rather than looking through test methods which iswhere they are currently.


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Better Isolation means better methods!

public function testUpdateModel():void{

var childVO:ChildVO = childPM.vo as ChildVO;

childPM.updateModel('@');

assertEquals('This is the

childVO@', childVO.title);}

//really a functional test./* public function testUpdateParentModel():void{

var parentVO:ParentVO = parentPM.vo as ParentVO;

childPM.updateParentModel('@')assertEquals('This is a parentVO it

has the child VO@',parentVO.id);}*/

public function updateModel(value:*='*'):void{

if(value!='*')value='@';childVO.update(value);

//Don't do this its then doing two things atonce implicitly;

//if(parentPM)//parentPM.updateModel('*');

//Instead do this you can test this!!!updateParentModel(value);

}

public function updateParentModel(value:*):void{

if(parentPM)

parentPM.updateModel(value);}

ChildPMTest ChildPM

A setup method that should be made of a context file(s) and


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A setup method that should be made of a context file(s) andinjected.override public function setUp():void

{//This stuff should be in a ContextFile.var localisedSettings:LocalisedSettings = new LocalisedSettings({});localisedSettings.addProperties({'dh_Ranger_Thousand_Separator':','});localisedSettings.addProperties({'dh_Ranger_Decimal_Separator':'.'});var configurationSettings:Object = {'dh.ranger.flex.defaultcurrencysymbol':'','dh.ranger.flex.currencysymbolalign':'L'};

presentationModel = new ProductGroupsModulePM(1, configurationSettings, localisedSettings);presentationModel.dendrogramData = new DendrogramData([],{},[]);

//CREATES SEG DATA ON MODEL.createSegmentationData();

var level1GroupVO:GroupVO = new GroupVO();level1GroupVO.GroupId = 10;

level1GroupVO.GroupProducts = createFourGroupedProductsNoneExcluded();

groupVO = level1GroupVO;presentationModel.groups.addItem(level1GroupVO);

var productDataAttributeVO1:ProductDataAttributeVO = new ProductDataAttributeVO();

productDataAttributeVO1.AttributeValue = "1000";productDataAttributeVO1.ColumnName = "test";productDataAttributeVO1.ProductCode = "12345";

var productDataAttributeVO2:ProductDataAttributeVO = new ProductDataAttributeVO();productDataAttributeVO2.AttributeValue = "2000";productDataAttributeVO2.ColumnName = "test";productDataAttributeVO2.ProductCode = "12346";



var attrs1:Object = { "test": productDataAttributeVO1};var attrs2:Object = { "test": productDataAttributeVO2};var attrs3:Object = { "test": productDataAttributeVO3};var attrs4:Object = { "test": productDataAttributeVO4};

var productCodeReferenced_productDataAttributeVO_ObjectProxies:Array =[

new ObjectProxy({ "12345": attrs1 }), new ObjectProxy({ "12346": attrs2}), new ObjectProxy({ "12347": attrs3 }), new ObjectProxy({ "12348": attrs4 })];var productData:Array = productCodeReferenced_productDataAttributeVO_ObjectProxies;

var productMetaDataVO:ProductMetaDataVO = new ProductMetaDataVO();productMetaDataVO.ColumnName = "test";productMetaDataVO.IsVisible = true;productMetaDataVO.ResourceKey = "test";productMetaDataVO.FormatType = FormatTypeVO.NUMBER;productMetaDataVO.FormatPrecision = 2;

productMetaDataVO.FormatMagnitude = null;productMetaDataVO.VisibleToProductMetrics = true;productMetaDataVO.VisibleToGroupMetrics = true;productMetaDataVO.VisibleToGroupSummary = true;productMetaDataVO.VisibleToProductSubstitutes = true;


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Having a setup with reusable stubs.

override public function setUp() : void{

var context : Context= ActionScriptConte

xtBuilder.build(ExampleASConfig);context.createDynamicContext().addObject(this);

}


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The Container - Formalises DI

One can look at a class and distinguish more easily betweendepended on and composite objects - ones that live and diewith the class as opposed to those that live on (aggregate). The[Inject] metadata tag makes highlight the classes

dependencies.


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Links http://www.spicefactory.org/parsley/

http://opensource.adobe.com/wiki/display/cairngorm/OptionsConstructRetrieveIsolateObjects

http://www.javaranch.com/unit-testing/http://opensource.adobe.com/wiki/display/cairngorm/BestPracticesAgileUnitTestinghttp://www.javaranch.com/unit-testing/too-functional.jsp

http://www.javaranch.com/unit-testing/software-testing-vocabulary.jsp
http://www.javaranch.com/unit-testing/software-testing-vocabulary.jsphttp://www.javaranch.com/unit-testing/too-functional.jsphttp://opensource.adobe.com/wiki/display/cairngorm/BestPracticesAgileUnitTestinghttp://www.javaranch.com/unit-testing/http://opensource.adobe.com/wiki/display/cairngorm/OptionsConstructRetrieveIsolateObjectshttp://opensource.adobe.com/wiki/display/cairngorm/OptionsConstructRetrieveIsolateObjectshttp://opensource.adobe.com/wiki/display/cairngorm/OptionsConstructRetrieveIsolateObjectshttp://www.spicefactory.org/parsley/http://www.javaranch.com/unit-testing/software-testing-vocabulary.jsphttp://www.javaranch.com/unit-testing/software-testing-vocabulary.jsphttp://www.javaranch.com/unit-testing/too-functional.jsphttp://opensource.adobe.com/wiki/display/cairngorm/BestPracticesAgileUnitTestinghttp://opensource.adobe.com/wiki/display/cairngorm/BestPracticesAgileUnitTestinghttp://www.javaranch.com/unit-testing/http://opensource.adobe.com/wiki/display/cairngorm/OptionsConstructRetrieveIsolateObjectshttp://opensource.adobe.com/wiki/display/cairngorm/OptionsConstructRetrieveIsolateObjectshttp://opensource.adobe.com/wiki/display/cairngorm/OptionsConstructRetrieveIsolateObjectshttp://www.spicefactory.org/parsley/http://www.spicefactory.org/parsley/


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Links

The container also facilitates a more decoupledcomponentized structure for presentation models see:http://blogs.adobe.

com/tomsugden/2009/08/applying_the_presentation_mode.htmlhttp://www.adobe.com/devnet/flex/articles/ioc_frameworks.html

http://martinfowler.com/articles/injection.html#ConcludingThoughts
http://www.adobe.com/devnet/flex/articles/ioc_frameworks.htmlhttp://blogs.adobe.com/tomsugden/2009/08/applying_the_presentation_mode.htmlhttp://blogs.adobe.com/tomsugden/2009/08/applying_the_presentation_mode.htmlhttp://blogs.adobe.com/tomsugden/2009/08/applying_the_presentation_mode.htmlhttp://martinfowler.com/articles/injection.html#ConcludingThoughtshttp://martinfowler.com/articles/injection.html#ConcludingThoughtshttp://www.adobe.com/devnet/flex/articles/ioc_frameworks.htmlhttp://blogs.adobe.com/tomsugden/2009/08/applying_the_presentation_mode.htmlhttp://blogs.adobe.com/tomsugden/2009/08/applying_the_presentation_mode.htmlhttp://blogs.adobe.com/tomsugden/2009/08/applying_the_presentation_mode.html

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IOC Containers and Unit Testing