I was asked by a colleague today how to perform string concatenation in a web test for a query string they were wanting to be built up of some content from the data context and a hardcoded value. They wanted to do this without resorting to code in a plugin.

In order to support this the web test can simply have the hardcoded value next to the datacontextvalue i.e. "MyHardcodedString{{MyDataContextValue}}"

The web test will parse out and replace the data context value for you and do the concatenation. In this case they put this in their query string, but the same principle could be used in other places such as form posts also. Often this principle is used when replacing values from web service calls as the {{MyDataContextValue}} value can be pulled out and replaced with a data context bound value such as something from a datasource. See the docs on MSDN for more information on the seb service databinding: http://msdn2.microsoft.com/en-us/library/ms182546(VS.80).aspx