When running a fixture without a corresponding specification, I see the error:

no specification extensions defined for: Concordion.NET.Internal.SpecificationConfig

I found this confusing. It would be better to display an error that the specification could not be found, and list the specificiation file that we are trying to open.

Note: there are some changes in this area for Concordion 2.0.0, since we now try to open a number of different specification types.