Error "The expression ['$Agent.NUnit.3.0.Path$' exists] evaluated False" when trying to run NUnit from final builder?

I'm trying to run some unit tests using Final Builder Continua but nothing I try seems to work. I've configured a Unit test stage:

But everytime I run the build I get the error:

The expression ['$Agent.NUnit.3.0.Path$' exists] evaluated False

then the whole thing hangs. There are several issues reported on the final builder forums but the soliutions all relate to older versions or various other fixes none of which seem to apply to my situation.

I'm guessing it doesn't know where the NUnit console is. I have tried specifying the missing parameter in the build config for the agent:

I've tried installing NUnit from nuget

nuget install nunit

Has anyone any experince of this or solutions to this issue?

I'm using continua 1.8.1.277

It's not practical for Continua CI to know all possible installation locations for NUnit. If installed using NuGet then it will be installed under the current directory by default - this installation folder can be changed using the OutputDirectory parameter for NuGet.

Editing the property collector search path is not considered to be a hack - it is actually a recommended solution if you know the path of the executable.

Another equally valid solution would be to add the path to the executable to the PATH environment variable on your agent. As of v1.8.1.556, Continua CI will automatically pick up changes to the PATH variable without restarting agent service.

Note that the NUnit action also provides a option to install the executable using NuGet as part of the build:

Ticking the "Install NUnit on agent using NuGet" will show a NuGet tab allowing you to enter the NuGet install parameters.

You can also choose "Custom" in the Using drop-down. This allows you to specify the path to the executable to use for this action.