Strange issue with Razor not updating in Tests

[oatsoda]

I've got a strange issue which seems to be occurring within bUnit tests, but which does not occur when running in Blazor.

I've got a Component whose Razor doesn't appear to update.

The (simplified) situation is this (in actuality, this Component is not the Subject Under Test, but actually one of the child components rendered as part of the Component Under Test).

Razor

<p>@Profile.FirstName</p>

Code-behind

public UserProfile Profile { get; set; }

override OnInitialized() 
{
    FluxorStore.StateChanged += OnStateChanged;
}

private async void OnStateChanged(object? sender, EventArgs e)
{
     UserProfile = FluxorStore.Value.Profile;  // Profile has a populated FirstName when Fluxor store changes, I have logged to output to check
     await InvokeAsync(StateHasChanged);
}

public record UserProfile(Guid Id, string FirstName);

When I run the test, then I use a WaitForState() call to check that the <p> value updates, but it never updates; the HTML rendered is <p></p>.

But if I run in Blazor then it works fine.

However, if I make a change, and add a this property to the Razor and code behind

<p>@FirstName</p>

public string FirstName { get; set; }

and change the OnStateChanged to set that value before the StateHasChanged is triggered:

FirstName = UserProfile.FirstName;

Then it correctly renders!

Any ideas what could be happening here?

[linkdotnet]

Hey,

without your test code it is really hard to tell. Could your provide that to have a better understanding?

On top of my head you have an asynchronous action, so depending on the circumstances you have to await some state in the test.

[oatsoda]

@linkdotnet Changing it to private void OnStateChanged and using StateHasChanged() doesn't impact the result.

I have logging in the handler which prints out UserProfile.FirstName to prove that it has the correct value (and that it doesn't subsequently get overwritten).

But still the razor does not display the UserProfile.FirstName value - yet it will display the copied value in FirstName.

Does bUnit have it's own custom rendering code, or does it use the actual Blazor rendering?

I can't share my code yet. I'm trying to reproduce in a simpler scenario, but unsuccessfully so far...

[linkdotnet]

I am not sure what you mean with "changing it to private void OnStateChanged.

Could you provide some test code to have a common ground for discussions?

It uses actual Blazor pipeline. But bUnit tries to be very sychrnonous like Blazor itself, that can lead to "problems" with async code.
In those scenarios we have to use WaitFor stuff.

[oatsoda]

@linkdotnet Thanks for the reply. I meant even if I change it to be sync instead of async.

I think I may have actually just found my issue. It looks like the OnParametersSet had functionality which during Tests executed so fast that it overwrote the data set in the OnStateChanged :(