VSTS 2010 Feature: Making it easy to debug web tests using Fiddler

VSTS 2010 Beta2 is out and there are a number of blog posts I want to write on the features now available to you.  Check out Ed Glas’s blog post on the full set: Beta2 Features

The first small feature that I am going to talk about is better integration with Fiddler.  If you are not familiar with Fiddler, it is Web Debugging Proxy and is very useful when debugging web tests.  You can find Fiddler here: Fiddler  There are times when debugging a web test that it is helpful to get another view of the data that is being sent to the servers you are testing.  It has been possible to use fiddler for these purposes since VS 2005, but we have made it much easier.  In VS 2005 or VS 2008 or even VS 2010 Beta1, you had to write a small bit of code to correctly hook up to fiddler.  The code you would have to add looked like the following and needed to be added in the constructor of a coded test or a in a web test plug-in:

this.Proxy = “http://localhost:8888“;
WebProxy webProxy = (WebProxy)this.WebProxy;
webProxy.BypassProxyOnLocal = false;


With the beta2 release we have made this even easier.  Now to get Fiddler to capture the traffic from your web tests, you just need to do the following:

  1. Launch Fiddler
  2. Play your web test

That is it.  No code to write or any extra configuration.  We have only made this work when you are running a web test by itself.  If the web test is running as part of a load test, the traffic will not be routed through fiddler.  You could still use the old method to get this to work if needed.

I will be writing a few more blog posts in the coming weeks on the new features, so please try them out and let us know what you think.

Comments (2)

  1. Running web Test as part of load Test says:


    my web test is running as part of a load test and i have to use fiddler to debug the test for monitoring the http traffic.

    When i run only web performance test then i can see all the http request and response but when i run the actual load test then i can not see actual http traffic in fiddler debugger.

    i have checked capture traffic from File menu.

    can u please provide me steps if i missed anything??

  2. Mishal says:

    Hey, I am using VSTS 2010 and when I tried to replay a recorded script, while fiddler is on, I got 'Access Denied' / 'Authentication'error ; when I replayed the same script, after closing the Fiddler, it ran successfully.

    Do anyone know how to solve this issue??