Available on Labs.
Info cribbed from the Labs page:
The Flex Data Services Stress Testing Framework helps Flex developers using Flex Data Services load test their Flex 2 applications. Flex Data Services offers a number of data transport channels for communicating between a Flex client and the Flex Data Services server. These channels include RTMP(s), AMF(s) and HTTP(s). Most commercial load testing tools rely on data being sent over HTTP and less performing implementations of the AMF protocol (usually AMF0). Flex Data Services enables developers to leverage HTTP in addition to the latest and highest performing version of AMF (AMF3) and data push with RTMP. As most load testing tool vendors have not yet released support for RTMP(s) or the latest version of AMF(s), the Flex Data Services Stress Testing Framework allows Flex developers to load test their applications that use RTMP and AMF3 without needing to use a commercial testing tool.
Adobe is currently working with a number of testing tool vendors to implement all of the data transport protocols available in Flash. In addition to partnering with testing tool vendors, we are providing the following load testing framework to enable Flex Data Services developers to load test their applications. The Flex Data Services Stress Testing Framework is currently in beta form, but available for testing and evaluation. Please download and test the framework and provide us your feedback.