Data Binding in Web Tests
You can use data binding in a Web test to provide the input to HTTP requests in the Web test. For example, you could provide a list of logon names and logon passwords that would be used during the execution of the Web test to try repeated logons.
You can examine your Web tests and decide which part of a test you want to be data-driven. Then you can create a data source for that part of the test. You can bind data in several locations in a Web test. For more information, see About Data Binding in Web Tests.