The Performance Test is a great new feature for determining how an Azure Web App will perform under pressure by simulating workloads. This feature is in preview and is being developed by the Azure Websites and Visual Studio Load Testing teams.
For an introduction please see the Public preview for Performance Test on web and mobile apps post.
As a summary, the Performance Test feature can be accessed in the Tools section of an Azure Web App in the Azure Portal. At the moment it supports running a simple load test against a specified url. For example performing a load of 250 concurrent users over 5 minutes.
The performance test is being run from a Visual Studio Online account. From within Visual Studio Online more sophisticated tests can be run including those defined using the Visual Studio Test Suite and JMeter scripts.
Another great feature added to Web Apps