To create an external scriptable variable, in Visual Studio create a new class library project. Then add a reference to StresStimulus extensibility API located in the  StresStimulus.Extensibility  namespace using the following assembly:

  • In standalone version, use namespace is located in the  StresStimulus.Core  assembly
  • In Fiddler add-on version, use namespace is located in  StresStimulus.Core.Fiddler  assembly


If you wish to use your custom External Scriptable Variables with both StresStimulus versions, create/compile two versions of the extensions using the same codebase, but referencing two different StresStimulus assemblies.

Your assembly should be stored into the Bin subfolder in the test folder. For example, for the test MyTest.ssconfig, copy the assembly dll to MyTest\bin folder.

Programming of the External Scriptable Variables is similar to programming the Internal Scriptable Variables. 

.NET versions

StresStimulus is built on .NET 3.5, however, it runs seamlessly on machines that have .NET 3.5 and/or .NET 4 Framework. However, this becomes important when building external StresStimulus extensions. Particularly, extensions built in .NET 4 will not load on .NET 3.5. If you built an extension in .NET 4 and have .NET 3.5 and .NET 4 installed on your machine then do the following:

Standalone Version:

In StresStimulus install directory, find file StresStimulus.Application.exe.config.  Open and remove the line <supportedRuntime version="v2.0.50727"/> and save it. After that, StresStimulus will launch under .NET 4.0.  You would need to make this change again after every StresStimulus reinstall/update.

Fiddler addon:

Use Fiddler4 (not Fiddler2). StresStimulus will run inside Fiddler process under .NET 4.0. This workaround does not require you to make any changes after StresStimulus reinstall/update. StresStimulus add-on version has all features of the standalone version plus Fiddler integration.

Distributed Testing:

If using external variables in a distributed testing environment, it's important to consider what version of StresStimulus is running on the controller and agents being used.

  • If the controller is running standalone version, the agents must be running a standalone version or as a Windows service.
  • If the controller is running Fiddler add-on version, the agents must be running Fiddler add-on version.


External Components

The information provided in this section also pertains to external components.

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