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In the following example I will show how easy it is to isolate your client code from ASP.NET code, using the Moles Isolation Framework, in order to test that your code performs as intended.
The example should not be seen as an encouragement to use bad design. On the contrary, I urge you to use Moles to get that ugly, old legacy code you’ve got, and put it under test such that you will have the freedom to rip it apart and improve it.
Now Moles will generate an assembly with mocks and stubs of the target assembly (System.Web) and add it to the test project. Your references should look like this:
Now you are ready to start writing tests. First we take a look at our sample application. It is a simple ASPX-page which calls Server.MapPath() in the Page_Load method:
public partial class ServerUsageExamplePage : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { //... Server.MapPath("...");
//... } }
In our unit test we want to be able to replace the call to Server.MapPath() such that
The following test method will fake the call to Server.MapPath() and assert that it was actually called by the method under test:
[TestMethod] [HostType("Moles")] public void MapPath_WhenCalledWithProperContext_ShouldInvokeServerMethod() { // Arrange var mapPathWasCalled = false; MHttpContext.CurrentGet = () => new MHttpContext { ServerGet = () => new MHttpServerUtility { MapPathString = path => { mapPathWasCalled = true; return string.Empty; } } };
// Act var page= new ServerUsageExamplePage(); page.Page_Load(this, EventArgs.Empty);
// Assert Assert.IsTrue(mapPathWasCalled); }
To accomplish this we need to understand what is going on. “Server” is an instance property on the System.Web.UI.Page class which eventually will invoke the HttpContext.Current.Server property. Thus, to fake the method call we need to fake several things:
Finally, to be able to execute the method under test (Page_Load), we need to change its accessibility from protected to public.
I've shown how easy it is to get started covering your ASP.NET codebehinds with unit tests utilizing Moles Isolation Framework. This article will be followed up with more examples on how to leverage Moles. Please leave feedback and any questions you might have. Good luck testing!
Moles is a new framework from Microsoft Research for isolating objects in unit tests. With the framework you create test stubs by using delegates and you can route any .NET method you want, including non-virtual and static methods in sealed classes. In addition, the framework is free, making it a major competitor to TypeMock Isolator that has been alone on this functionality for a long time.
Moles automatically generates stubs for all classes in one assembly. Here is an example of how easy it is to change the behavior of the static DateTime.Now property:
// change the value of DateTime.Now MDateTime.NowGet = () => new DateTime(2000,1,1); if (DateTime.Now == new DateTime(2000,1,1)) throw new Y2KBugException();
Mole’s strength to fake and reroute static methods and the like makes it a very powerful tool for isolating and unit testing code developed for SharePoint. Microsoft Research has a whitepaper that describes how to get started:
Unit Testing SharePoint with Microsoft Foundation Pex and Moles
Here is a video that introduces Moles: