Recording VS.NET Web Performance Test for Flex

We are building a web application that integrates with a third party software by embedding their Flex objects in our ASPX pages. When we started using VS.NET 2010 Web Performance Test, everything worked fine except for the weborb requests made by the Flex objects to the server. Basically, the requests recorded by the web test, when played back and sent to the server, were causing the server to respond with errors. From googling, it looks like that the same issue has been experienced by other folks as well. At this point, it would be easy to simply dismiss VS.NET 2010 Web Performance Test as a viable tool for Flex. What a costly mistake this would have been if we had stopped doing more analysis!

Looking at the initially recorded tests, I found out that all the data posted by the Flex objects was recorded and played back as string data type. Examining the payload in Fiddler, however, showed that the data is obviously binary. So our recorded test was sending the data with lost fidelity and the server just choked.

Thinking that there must be configuration to tweak to make our tests record binary data, I started searching MSDN for documentation. Sure enough, I found this link. I went ahead and added "application/x-amf" as the content type. Then I recorded the test again and ran the scripts.

Voila, everything worked like a charm!