Expand test harness (#6)

WoofWare.PawPrint/AbstractMachine.fs

@@ -470,7 +470,12 @@ module IlMachineState =
                     with :? FileNotFoundException ->
                         None
                 )
-                |> Seq.exactlyOne
+                |> Seq.toList
+
+            match assy with
+            | [] -> failwith $"Could not find a readable DLL in any runtime dir with name %s{assemblyName.Name}.dll"
+            | _ :: _ :: _ -> failwith $"Found multiple DLLs in runtime dirs with name %s{assemblyName.Name}.dll"
+            | [ assy ] ->
 
             state.WithLoadedAssembly assemblyName assy, assy, assemblyName