There are many advantages for unit testing Silverlight with Typemock Isolator. These include shortening the development cycle, reducing the development costs, increasing code coverage, releasing a product with less bugs, providing good documentation and more...

Microsoft Silverlight runs with its own version of .Net runtime. Up until now, it was not possible to isolate Silverlight code in tests. But now, thanks to SilverUnit, built on top of Typemock Isolator, it is possible to test Silverlight with ease.

SilverUnit does not require that you run your tests inside the Silverlight runtime. You can run your regular NUnit or MSTest tests only in-memory. The CThru engine underneath SilverUnit takes care of intercepting and “skipping” all calls to the Silverlight runtime. SilverUnit does its part and mimics the missing pieces (Dependency Properties, RoutedEvents, and so on), so you wouldn't need to write them yourself.

SilverUnit is the first implementation of CThru, targeted specifically at testing Silverlight applications. CThru is an AOP (Aspect Oriented-Programming) open source project based on a new Typemock Isolator feature set called "Open AOP" that allows you to intercept any call in a precompiled system (SharePoint, Silverlight, etc.) and change its behavior.  

The following video shows the differences between silverunit and the MS silverlight test framework. SilverUnit is shown in the second half of the presentation.

Unit Testing Silverlight Code Sample VB.NET

Below you can see a unit testing Silverlight code sample. This test sets dependency properties and checks what happens when an Invalid value is set on them. The next one uses two controls with each other.

<SilverlightUnitTest(), Test()> _
        Public Sub MinimumPrefixLength_SetToLessThanMinusOne_ResetsToMinusOne()
        Dim box As AutoCompleteBox = New AutoCompleteBox
        box.MinimumPrefixLength = -3
        Assert.AreEqual(-1, box.MinimumPrefixLength)
    End Sub
 
  <SilverlightUnitTest(), Test()> _
    Public Sub SetTextBox_SetTextOnCompleteBox_TextBGoxIsUpdatedWithCompleteBox()
        Dim txt As TextBox = New TextBox()
        Dim box As AutoCompleteBox = New AutoCompleteBox()
        txt.SelectionStart = 0
        txt.SelectionLength = 0
 
        box.TextBox = txt
        box.Text = "a"
        Assert.AreEqual("a", box.Text)
        Assert.AreEqual(box.Text, txt.Text)
 
    End Sub
      

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Resources

• Silverlight Unit testing - SilverUnit and CThru on codeplex.com with code sample
• SilverUnit source code - Testing Silverlight-Source code for SilverUnit
• Unit testing Silverlight - Silverlight unit testing - Silverlight tutorial
• Silverlight Tutorial - Silverlight tutorial for Silverlight unit testing
• Tutorial Silverlight - Tutorial Silverlight unit testing