anchor.diff:          |> Seq.distinctBy (fun x -> x.Key)
           |> System.Collections.Concurrent.ConcurrentDictionary
   
  -    let langServices = TestHostLanguageServices(this, LanguageNames.FSharp)
  +    let langServices = TestHostLanguageServices(this, LanguageNames.FSharp, exportProvider)
   
       override _.Workspace = workspace
   
  
positive.code:         |> Seq.append MefHostServices.DefaultAssemblies
          |> Array.ofSeq
  
      let exportProvider =
          let resolver = Resolver.DefaultInstance
          let catalog = 
              let asms = getAssemblies()
  
negative.code:                             //"Microsoft.CodeAnalysis.LanguageServer.Protocol.dll"
                             // "Microsoft.CodeAnalysis.Features.dll"
                              "Microsoft.CodeAnalysis.Workspaces.dll"
                             // "Microsoft.CodeAnalysis.EditorFeatures.dll"
                            //  "Microsoft.CodeAnalysis.CSharp.EditorFeatures.dll"
                            //  "Microsoft.CodeAnalysis.EditorFeatures.Text.dll"
  