Angular 9 TestBed.inject & Provider Overrides

let valueServiceSpy: jasmine.SpyObj<ValueService>;

beforeEach(() => {
  const spy = jasmine.createSpyObj('ValueService', ['getValue']);

  TestBed.configureTestingModule({
    providers: [
      { provide: ValueService, useValue: spy }
    ]
  });
  // This is new way to inject Spied Service
  valueServiceSpy = TestBed.inject(ValueService) as jasmine.SpyObj<ValueService>; 
});

and then in tests

it('#getValue should return stubbed value from a spy', () => {
  valueServiceSpy.getValue.and.returnValue(yourValue);
  ...
});

Ref

For all intents and purposes, your MyStub should at least be a Partial or a class that extends the class it's trying to mock, otherwise your tests are kinda 'wrong', so if that's the case you can just do:

const obj = TestBed.inject(MyClass);

If you somehow will have different properties or different function signatures on your stub, you can also do this:

const obj = TestBed.inject<MyStub>(MyClass as any);

But generally speaking, your mocks should (partially) share the same signature as the thing it's mocking, which also means there is no need for casting