ReactiveUI Testing - reactiveui

Question

I am attempting to see if the results of a view model are performing the correct actions.
My observables are setup as follows:
public FilterBoxViewModel()
{
var asyncFilterResults = this.filterItemsCommand.RegisterAsyncTask(x =>
this.PerformFilter(x as string));
this.filteredItems = new ObservableAsPropertyHelper<IEnumerable<IFilterBoxItem>>(
asyncFilterResults, _ => this.RaisePropertyChanged("FilteredItems"));
this.WhenAnyValue(x => x.SearchTerm)
.Throttle(TimeSpan.FromMilliseconds(50))
.Skip(1)
.Subscribe(this.filterItemsCommand.Execute);
}
Then further down I have
private async Task<IEnumerable<IFilterBoxItem>> PerformFilter(string searchTerm)
{
if (string.IsNullOrWhiteSpace(searchTerm))
{
return Enumerable.Empty<IFilterBoxItem>();
}
// Perform getting the items on the main thread and async await the results.
// This is provide a immutable version of the results so we don't cause
// threading issues.
var items = await Observable.Start(
() => this.FilterBoxManager.RootElements.GetAllItemsEnumerable()
.ToList().Select(x => new { Name = x.Name, Item = x }),
RxApp.MainThreadScheduler);
return
items.Where(x =>
x.Name.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0)
.Select(x => x.Item);
}
In my test, I am running the test schedular and advancing it, however, I am getting the PerformFilter performing at different times than I expect
eg my test is:
(new TestScheduler()).With(scheduler =>
{
var viewModel = new FilterBoxViewModel();
var testManager = new TestManager { RootElements = this.sampleItems };
viewModel.FilterBoxManager = testManager;
viewModel.SearchTerm = "folder";
scheduler.AdvanceBy(TimeSpan.FromMilliseconds(51).Ticks);
Assert.AreEqual(viewModel.FilteredItems.Select(x => x.Name), folderSearchResults);
viewModel.SearchTerm = "apple";
Assert.AreEqual(viewModel.FilteredItems.Select(x => x.Name), appleSearchResults);
});
How do I make the tester more predictable?
I am running ReactiveUI 5.5.1 and in a XAML application.

Answer 1

Your Throttle doesn't set a scheduler, this is a classic TestScheduler mistake