Web Performance Test Engine Overview
Understanding how the Web performance test engine works can help you correctly create and configure your Web performance tests.
A key concept to understand about the Web Performance Test Engine is that Web Performance Tests work at the HTTP layer. Web Performance Tests contain a list of HTTP requests; each of these requests is primarily made up of querystring parameters, form parameters, and a URL that targets a Web server. The Web Performance Test Engine executes these HTTP requests, retrieves the responses from the server or servers, and collects timing data.
A common misconception is that because recording occurs in Internet Explorer, and the Web Performance Test Result Viewer displays results in a browser control, Web performance tests must somehow execute using Internet Explorer. This is not the case. All requests are executed directly using the Web Performance Test Engine; no interaction with Internet Explorer or any other browser occurs. The Web Performance Test Engine communicates directly with the target Web server using standard HTTP request/response messages.
Another source of confusion is that different browser templates can be selected when you run Web load tests. These browser templates only affect the default set of HTTP headers sent with each request. The key header that Web servers use to determine the browser type is the UserAgent header. The Web Performance Test Engine issues requests directly using standard HTTP protocol regardless of which browser template is selected.