Using Ivonna and CThru for testing Asp.Net MVC Views, part 1

Wait, isn't MVC testable by design? Yes, most of it is testable, but as for the Views, you have to resort to integration tests (which isn't bad by itself, but sometimes is not enough).

In my recent project, I needed to write a test verifying that if a user is not authenticated, she should see a login form and a registration form. Speaking in terms of implementation, this means that Html.RenderPartial should be invoked with paths to my partial views containing these forms. Looks like a good task for TypeMock Isolator, but I prefer working with CThru. Here's the test code (forgive me for not following the strict rules, such as one assert per test, this is just for clarity):

Imports WebTests.Infrastructure
Imports Ivonna.Framework
Imports MbUnit.Framework
 
Namespace Membership
     _
    Public Class OwnersPage_NotLoggedIn
         _
        Public Sub ContainsLoginPartial()
            'Arrange
            Dim spy As New RenderPartialSpy
            CThru.CThruEngine.AddAspect(spy)
            Dim session As New TestSession
 
            'Act
            session.ProcessRequest(New WebRequest("Owners"))
 
            'Assert
            Assert.Contains(spy.ViewNames, "~/Views/Account/Login.ascx")
            Assert.Contains(spy.ViewNames, "~/Views/Account/Register.ascx")
        End Sub
    End Class
End Namespace

The RenderPartialSpy class can be reused (this is why I prefer CThru), here's the code for it:

Imports CThru
Imports System.Web.Mvc.Html
 
Namespace Infrastructure
  Public Class RenderPartialSpy
    Inherits Aspect
 
 
    Public Overrides Function ShouldIntercept(
      ByVal info As CThru.InterceptInfo) As Boolean
      Return info.TypeName.Contains("RenderPartialExtensions") AndAlso info.MethodName = 
        "RenderPartial"
    End Function
 
 
    Private _viewNames As New List(Of String)
    Public ReadOnly Property ViewNames() As IList(Of String)
      Get
        Return _viewNames
      End Get
    End Property
 
    Public Overrides Sub MethodBehavior(ByVal e As CThru.DuringCallbackEventArgs)
      Me.ViewNames.Add(e.ParameterValues(1))
      MyBase.MethodBehavior(e)
    End Sub
 
  End Class
End Namespace

Here I just set it to intercept all calls on the RenderPartialExtensions class with the method name "RenderPartial". When the call is intercepted, I save the value of the second argument (remember this is an extension method) in my list. At the Assert stage, I'll be able to retrieve all saved values and check them.

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)