All Hail Fiddler v1.2.2.2 Beta!

The long and short of this post is that if you want to use the VSTS web tests from Fiddler with ASP.NET AJAX applications, use the beta, not the v1.2 release. You can find the beta at

www.fiddlertool.com/dl/fiddlerbetasetup.exe

In case you haven't heard of it before, Fiddler is a tool that records HTTP requests and responses.

It is similiar in concept to the web test recorder that is part of VSTS, but it ties into the Internet Explorer object model much closer. The most obvious benefit to doing so is that it can record ASP.NET AJAX requests.

In terms of ASP.NET, the VSTS web test recorder will only capture HTTP traffic when it is sent 'properly' by the browser. That is an ASP.NET full postback or a browser refresh.

Of course, the whole idea of AJAX is to minimize full postbacks. The ASP.NET AJAX toolkit does a remarkable job of writing AJAX enabled web applications.

The problem that this causes for VSTS is that VSTS can't pick up the AJAX requests back to the server; so these types of applications are very hard to test.

This is where Fiddler comes into play. Fiddler can pick up the AJAX requests and emit a VSTS web test from it.

Now, the version of Fiddler that I used was the release version v1.2. That version has a bug where form field names are not recorded properly. Not sure what all the scenarios are that cause this, but ASP.NET AJAX applications are definitely one of them.

The version that you want is here www.fiddlertool.com/dl/fiddlerbetasetup.exe.

Fiddler does a really nice job of emiting a VSTS web test that you can put into a test project.

Thanks!

Eric.