Scott Hanselman

NUnit Unit Testing of ASP.NET Pages, Base Classes, Controls and other widgetry using Cassini (ASP.NET Web Matrix/Visual Studio Web Developer)

December 01, 2004 Comment on this post [6] Posted in ASP.NET | NUnit | Bugs
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There's a lot of info out there on how to cobble together NUnit Unit Testing of ASP.NET Pages and assorted goo. NUnitASP is a nice class library to facilitate this kind of testing, but it doesn't solve a few problems:

  • Do you have/want a Web Server on your Test/Build machine?
  • How do you get your Test Pages and such over to the Web Server? Just automatically copy them?
  • Are your Test cases self-contained? That is, do they require external files and other stuff to be carried along with them?

I have a need to test a number of utility classes, base classes for System.Web.UI.Page and other miscellany and I'd like the tests to be entirely self contained and runnable only with NUnit as a requirement.

So, here's a small solution we use at Corillian. I use Cassini, the tiny ASP.NET Web Server that brokers HTTP Requests to System.Web.Hosting and the ASP.NET Page Renderer. You may know Cassini as the precursor to the Visual Developer Web Server from Visual Studio "Whidbey" 2005. Cassini usually comes with two parts, CassiniWebServer.exe and Cassini.dll.  However, I don't want to launch a executables, so I'll just refer to Cassini.dll as that is the main engine.

using Cassini;



    public class WebTests


        private Server webServer;

        private readonly int webServerPort = 8085;

        private readonly string webServerVDir = "/";

        private string tempPath = AppDomain.CurrentDomain.BaseDirectory;

        private string tempBinPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory,"bin");

        private string webServerUrl; //built in Setup

Cassini is the 'private Server webServer' in the code above. I'm using a fairly random port, but you could certainly scan for an open port if you like. Note that I'm building a /bin folder, as Cassini's own ASP.NET Hostingn AppDomain will look for DLLs to load in /bin.

Cassini starts up another AppDomain, and that AppDomain then loads Cassini.dll AGAIN, except the new AppDomain has a different search path that includes /bin, so it won't find Cassini.dll in the current directory. Usually this problem is solved by putting Cassini.dll in the GAC, but I want this test to be self-contained, and since I'll need my other DLLs in /bin anyway...


public void Setup()


    //Extract the web.config and test cases (case sensitive!)





    //NOTE: Cassini is going to load itself AGAIN into another AppDomain,

    // and will be getting it's Assembliesfrom the BIN, including another copy of itself!

    // Therefore we need to do this step FIRST because I've removed Cassini from the GAC


    //Copy our assemblies down into the web server's BIN folder


    foreach(string file in Directory.GetFiles(tempPath,"*.dll"))


        string newFile = Path.Combine(tempBinPath,Path.GetFileName(file));

        if (File.Exists(newFile)){File.Delete(newFile);}




    //Start the internal Web Server

    webServer = new Server(webServerPort,webServerVDir,tempPath);

    webServerUrl = String.Format("http://localhost:{0}{1}",webServerPort,webServerVDir);



    //Let everyone know

    Debug.WriteLine(String.Format("Web Server started on port {0} with VDir {1} in physical directory {2}",webServerPort,webServerVDir,tempPath));


A couple of important things to note here. 

  • This method is marked [TestFixtureSetup] rather than [Setup] as we want it to run only once for this whole Assembly, not once per test.
  • We're copying all the DLLs in the current directory down to /bin for Cassini's use during the test, but we'll delete them in [TestFixtureTearDown] after Cassini's AppDomain.Unload.
  • We build webServerUrl and start Cassini (remember, it's the "webServer" variable).
  • At this point we are listing on http://localhost:8085/

Additionally, I've snuck a new method in, ExtractResource(). This takes the name of an Embedded Resource (one that is INSIDE our test assembly) and puts it into a directory. In this case, I'm using the current AppDomain's directory, but you could certainly use Path.GetTempPath() if you like.

private StringCollection extractedFilesToCleanup = new StringCollection();

private string ExtractResource(string filename, string directory)


    Assembly a = Assembly.GetExecutingAssembly();

    string filePath = null;

    string path = null;

    using(Stream stream = a.GetManifestResourceStream("Corillian.Voyager.Web.Test." + filename))


        filePath = Path.Combine(directory,filename);

        path = filePath;

        using(StreamWriter outfile = File.CreateText(filePath))


            using (StreamReader infile = new StreamReader(stream))







    return filePath;


The ExtractResource method takes a filename and directory (and could, if you like, take a namespace, although I've hardcoded mine) and pulls a file as a Stream of bytes that was embedded as a resource in our Assembly and puts it into a directory. Hence the name, ExtractResource(). There is a StringCollection called extractedFilesToCleanup that keeps track of all the files we'll want to delete at the end of these tests, in [TestFixtureTearDown].

At this point, I've got a web.config (which was important to my tests, and will be looked at by Cassini/System.Web.Hosting) and a test1.aspx and test2.aspx in my current directory. The Cassini Web Server is started up and listing on port 8085 for HttpRequests. I also turned Page Tracing on in the web.config which will allow me to make certain Assertions about what kinds of code were called by the Page and helper classes within the Cassini ASP.NET context.

I'll add a helper method to create HttpRequests and return the response as a string:

private string GetPage(string page)


    WebClient client = new WebClient();

    string url = new Uri(new Uri(webServerUrl),page).ToString();

    using (StreamReader reader = new StreamReader(client.OpenRead(url)))


        string result = reader.ReadToEnd();

        return result;



Now I can write some tests! My tests need to test things like the overridden behavior of custom BasePages (derived from System.Web.UI.Page) as well as some helper functions that require (to be TRULY tested) an HttpContext. However, I don't want the hassle of a CodeBehind or a lot of other files, and certainly not the effort of a whole separate test project, so I'll make my ASPX pages self contained using <% @Assembly %> directives. So, for example: 

<%@ Assembly Name="Corillian.Voyager.Web.Common" %>
<%@ Page Language="C#" Inherits="Corillian.Voyager.Web.Common.SharedBasePage" %>
<script runat="server">
    public void Page_Load(object sender, EventArgs e )
        Label1.Text = "Hello";
    <form runat="server">
            <asp:Label id="Label1" runat="server">Label

A test to determine if this page executed successfully might look like:


public void BasicSmokeTestOfWebServer()


    string result = GetPage("test1.aspx");

    Assert.IsTrue(result.IndexOf("Hello") != -1,"Basic smoke test of test1.aspx didn't find 'Hello' in response!");


You could easily expand your tests to include NUnitASP, or continue to use WebClient with specific HttpHeaders like accept-language or user-agent. One of our QA guys uses NUnit to automate the IE WebServer Control, the manipulates the DHTML DOM to make Assertions.

Finally, my cleanup code is simple, deleting all the files we extracted as well as toasting the /bin folder.


public void TearDown()




        if (webServer != null)



            webServer = null;








private void CleanupResources()




        foreach(string file in extractedFilesToCleanup)





    catch (Exception ex)





Now the WebServer, Test Cases and Test are nicely self-contained and can be moved to the CruiseControl.NET Continuous Integration Build Server. 

Enjoy. I did.

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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December 01, 2004 16:38
Well, I haven't tried running this code yet but it looks very useful. I would also be interested in hearing more about your "QA guys uses NUnit to automate the IE WebServer Control, the manipulates the DHTML DOM to make Assertions".

December 02, 2004 4:37
Sounds like a lot of work. Why not just dump that ASP.NET stuff and do smart client?

(Yes, I'm joking. I've considered establishing a screen name of "SmartClientTroll" and hitting every ASP.NET blog I can find with similar comments. But (1) I don't have the time, and (2) too many people would not appreciate the humor.)

December 02, 2004 18:52
Have you looked at NUnitASP? Pretty similar functionality to what you described.
December 23, 2004 4:23
Do you have/want a Web Server on your Test/Build machine?

If I am testing the aspx site, then yes I want to have a server on the Test/Build/Integration machine.

How do you get your Test Pages and such over to the Web Server? Just automatically copy them?

"Get and Build", just like the class libraries.

Are your Test cases self-contained? That is, do they require external files and other stuff to be carried along with them?

No, they are not an island, they explicitly depend on the presence of that which they must test.

Did you know you can do lots of stuff with nUnitAsp? Not just smoke tests for the content, but actualy click buttons and test the results; validation controls redirection etc. The bigest issue I have had with it is simple smoke tests and the constant churn from the html folks.

January 09, 2005 14:11
March 23, 2005 6:49
Have you seen SWExplorerAutomation( The tool allows to create Automation API for any Web application. The API can be used for writing nUnit tests.

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Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.