Developing Testable Silverlight Applications

Keith JonesSenior SDET - SilverlightMicrosoft Corporation

CL32

When Testability Matters> Your customer’s requirements just

changed> Your management wants a demo at

5:00> It’s the end game and your schedule

is tight

What Is Testability?> An application’s testability is the

inherent ability to efficiently isolate, evaluate, and communicate the application’s quality.

Effects of Poor Testability on Tests> Complicated setup/teardown> Too many points for failure> Too many unrelated verifications> High maintenance costs> Slow

Agenda> Separating concerns with M-V-VM> Decoupling with inversion of control> Using the Silverlight Unit Test

Framework> Leveraging .NET RIA Services> Testing the View

Model-View-ViewModel (M-V-VM)Background> Design pattern optimized for separation of

concerns on WPF and Silverlight> Heavily leverages data-binding> Encourages designers to own user

experience

Model-View-ViewModel (M-V-VM)Defining the pattern for testability

> Contains the controls and behaviors that make up the user interface

> Defined declaratively (if possible)> Adding code-behind is ok, but keep it thin

View ViewModel Model

Model-View-ViewModel (M-V-VM)Defining the pattern for testability

> Maintains View state> Exposes data points> Does not contain UI

View ViewModel Model

Model-View-ViewModel (M-V-VM)Defining the pattern for testability

> Simply data points

View ViewModel Model

Agenda> Separating concerns with M-V-VM> Decoupling with inversion of

control> Using the Silverlight Unit Test

Framework> Leveraging .NET RIA Services> Testing the View

Inversion of ControlSimplest solution> Dependency inversion with

parameterized constructors and interfaces

> Before public class Foo { Bar _bar; public Foo() { this._bar = new Bar(); } }

> After public class Foo { IBar _bar; public Foo(IBar barDependency) { this._bar = barDependency; } }

Inversion of ControlMost complete solution> Dependency injection (DI) containers> Register dependencies at application

startup> Resolve dependencies when needed

Inversion of Control +Model-View-ViewModel +Silverlight 4 = Better Testability

demo

Agenda> Separating concerns with M-V-VM> Decoupling with inversion of control> Using the Silverlight Unit Test

Framework> Leveraging .NET RIA Services> Testing the View

Silverlight Unit Test Framework Basics> Ships with the Silverlight Toolkit> API’s are nearly identical to VS unit

tests> Has some Silverlight specific features

> Tags> Asynchronous execution

Silverlight Unit Test FrameworkAsynchronous testing > Test execution is all on the UI thread> So are several crucial Silverlight operations> [Asynchronous] enables testing those

scenarios> Asynchronous tests are slow

Agenda> Separating concerns with M-V-VM> Decoupling with inversion of control> Using the Silverlight Unit Test

Framework> Leveraging .NET RIA Services> Testing the View

Intro to .NET RIA Services> Mission: Make n-tier RIA development as

easy as two-tier client app development> Prescriptive pattern for business logic on the

middle-tier: query and unit of work> RIA Services creates corresponding types for

your client app to use and handles the communication between the two tiers

> Write validation code once and have it applied on both the client and middle-tier layers

> Tooling to bring together web and Silverlight projects

Mid Tier

N-Tier Application with .NET RIA Services

> A domain model is a subset of the data from the store plus user types and business logic to solve a specific domain problem

Client DB

Domain Model

AppLogi

c

Data Bindable Domain Contexts

and Entities

DataClient and DataService

DataAppUI

Data Binding and Command

Binding

Code Generation

N-Tier Application with .NET RIA ServicesTesting strategy Mid TierClient DB

Domain Model

AppLogi

c

Data Bindable Domain Contexts

and Entities

DataClient and DataService

DataAppUI

Data Binding and Command

Binding

View ViewModel/Model Middle Tier Business Logic

Testing the Tiers with RIA Services and Silverlight 4

demo

Agenda> Separating concerns with M-V-VM> Decoupling with inversion of control> Using the Silverlight Unit Test

Framework> Leveraging .NET RIA Services> Testing the View

Testing the View Trains of thought> Use UIAutomation accessibility hooks to

programmatically control the UI> Send actual mouse clicks and keyboard

presses to simulate actual user actions> Register a browser plug-in to bridge desktop

testing capabilities with the ability to access internal application information

What’s Left To Test?The dirty work> End to end> Globalization> Security> Performance> Stress

Show off what you learned> Use Inversion of Control and M-V-VM

with Silverlight 4> Make use of RIA Services for your n-

tier applications

Resources> Relevant talks

> Building LOB Applications with SL4 [CL19]> Building Amazing Business Applications with Microsoft

Silverlight and Microsoft .NET RIA Services [CL21]> Mastering Microsoft .NET RIA Services [CL07]> Advanced Topics for Building Large-Scale Applications with

Microsoft Silverlight [CL22]> Links

> My Blog – http://blogs.msdn.com/keithjones/ > Silverlight Toolkit - http://www.codeplex.com/Silverlight > Bing – Keywords: Silverlight, MVVM, ViewModel, RIA

Services

Inversion of ControlUnity vs. MEF

Unity> .NET and Silverlight> Default DI container

mechanism for Composite Application Guidance (a.k.a. Prism)

> Supports many DI patterns and discovery and wireup mechanisms

MEF> .NET 4.0 and Silverlight> .NET 4.0 version is used

for new VS 10 extensibility

> Strength lies in extensibility, dynamic discovery, and auto-wireup

> Discovery through attributes limits use with existing assets

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