createStubInstance is not recognizing imported Angular typescript class constructor

[Rich Franzmeier]

I have a situation where I need to create an Angular component that has services to inject.  So I add providers using createStubInstance as shown:

        TestBed.configureTestingModule({

           imports: [DashboardModule, RouterTestingModule.withRoutes([{ path:'dashboard',component:DashboardComponent}])],

           providers: [

               { provide: UserProfileService, useValue: sinon.createStubInstance(UserProfileService) },

               { provide: NavService, useValue: sinon.createStubInstance(NavService) }

           ]

       }).compileComponents();

Enter code here...
This was working fine for me and then 'something' happened and now I get the error:  The constructor should be a function.

createStubInstance@http://localhost:9876/_karma_webpack_/vendor.bundle.js:351093:69

I don't know what that 'something' is and am wondering why it fails now. I debugged into it and the constructor parm is undefined

for UserProfileService in the createStubInstance method.

[Rich Franzmeier]

This turned out to be an issue in how I was using barrels (index.ts files) for exporting.  If I imported from the exact directory it worked.  If I imported from that parent directory (which had an index.ts file which also exported the child directory) it didn't work.  Not sure why.