I'm using Visual Studio 2015
I have a Shared Project as an Independent Solution (A collection of Extensions used in several others Solutions).
I want to TEST the Shared Project (Independently any other solution).
So, I add a new TEST Project.
But, in my TEST Project I can't add ANY reference to the Shared Project (No option).
Since a shared project can't be compiled on its own it cannot be added as a reference directly to a unit test project.
However, a work-around I've used is to create a helper class library and use that as a reference in the test project. In your case, create a new class library and call it RobHelperTest.Helper. This project won't contain any code on its own, so delete the class1.cs file. Since this is a class library, you can reference shared projects so simply add a reference to all your shared projects to RobHelperTest.Helper and then create a reference to RobHelperTest.Helper in your unit test project RobHelperTest.
Now you have full access to all your objects within the shared projects.
You can edit the project's csproj file and at end of imports add an entry like
<Import Project="..\SharedProject\SharedProject.projitems" Label="Shared" />
changing path & SharedProject as appropriate
probably best adding it to another project and copying the row created there (assuming same path depths)