If you are currently using VS 2008, here is how I compare the products and components you use for load testing.
VS Team System Test Edition
VS Team System Suite
VS Ultimate 2010
Client for developing load tests and web tests, running tests, and analyzing results. Enables limited “local” load generation from the same machine VS is on.
Test Edition is gone, load testing is only available in Ultimate.
Both VS 2008 and VS 2010 limit local load generation to one core. However, VS 2010 has the addition restriction of only allowing 250 virtual users.
Visual Studio Team System 2008 Test Load Agent
Visual Studio Load Test Virtual User Pack 2010
Product required for generating load
VU Packs are installed on the controller, and can be used on any number of agents.
VU Packs are just “paper licenses” that enable load generation.
VU Packs are tied to a controller, much like in VS 2008 Load Agent licenses were tied to the agent machine.
Visual Studio Test Controller
Distributes tests to agents, manages automated test runs, centralizes data collection from agents.
In VS 2008, the test controller is free when you purchase a load agent.
In VS 2010, the test controller is free when you purchase VS Ultimate, Premium, or Test Pro.
The 2010 test controller is used in a number of additional scenarios:
Lab management and provisioning test environment
Manages data collection agents for manual testing
Manages automated runs on Test Agents
Visual Studio Test Agent
The test agent allows distributed, parallel functional and unit test execution, as well as distributed data collection. The agent is also used as a load generator in conjuction with the Virtual User Pack on the controller.
VUser licenses are required on the controller to generate load.
See Test Controller for additional scenarios that are enabled.
If you licensed VS Team System Test Edition 2008 or Suite 2008 under SA, you can transition your license to VS Ultimate 2010 under the SA agreement. Similarly, if you purchased load agent licenses under SA we will also provide a transition from Visual Studio Team System 2008 Test Load Agent to Visual Studio Load Test Virtual User Pack 2010. Please refer to Licensing Whitepaper, EULA and/or Product Use rights for licensing requirements.