private IObservable <StateEvent> BuildExampleUseCase(IFakeApi client)
 => client.GetPosts()
 .Select(posts => new ResultState <IEnumerable <Post> >(posts))
 .StartWith <StateEvent>(new LoadingState())
 .Catch <StateEvent, Exception>(e => Observable.Return(new ErrorState()))
 .SubscribeOn(TaskPoolScheduler.Default)
 .ObserveOn(SynchronizationContext.Current);
 public FakeApiTests() : base(Array.Empty <string>())
 {
     _instance = _host.Services.GetRequiredService <IFakeApi>();
 }