Same problem, but i installed EF 6 through Nuget. EntityFramework.SqlServer was missing for another executable. I simply added the nuget package to that project.

Context: I am trying to run my tests on TeamCity which is currently installed on my machine. System.InvalidOperationException : The Entity Framework provider type ' System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer , Version=6.0.0.0, Culture=neutral, PublicKeyToken [your value] for the ' System.Data.SqlClient ' ADO.NET provider could not be loaded. Make sure the provider assembly is available to the running application. See http://go.microsoft.com/fwlink