Found the solution in the comments section of the same blog post. As I cannot link directly, it is quoted below:
BillyboyD
In case anyone needs to do something similar, I have managed to set this up so I can test my controllers in an ASP.NET Core project that targets the .NET Framework 4.6.1 and also references class libraries that are standard .NET, not .NET core (we will have this hybrid situation for some time!). I am using VS2015 update 3 and .NET Core 1.0. My project.json is:
{
"version": "1.0.0-*",
"testRunner": "mstest",
"dependencies": {
"dotnet-test-mstest": "1.0.1-preview",
"MSTest.TestFramework": "1.0.0-preview",
"MyASP.NetCoreProject": "1.0.0-*"
},
"frameworks": {
"net461": {
"dependencies": {
"MyClassLibrary": {
"target": "project"
}
}
}
}
}