bUnit WaitForAssertion passing on partial state during multiple render cycles

I have a Blazor component that performs multiple validations on an uploaded file. If both validations fail, it should show two separate alerts. In my bUnit test, I mock both validations to fail, yet Assert.Equal(1, alerts.Count())passes, even though I expect it to find 2 and fail.

It appears WaitForAssertion resolves as soon as the first error renders, rather than waiting for the logic to finish.

The Logic (Code Behind):

private void AddFilesToQueue(InputFileChangeEventArgs e){    try    {        var files = e.GetMultipleFiles();        foreach (var file in files)        {            if (!fileValidator.IsSizeValid(file.Size, ...)) {                filesOverMaxSize.Add(file);            }            if (!fileValidator.IsTypeValid(file.Name, ...)) {                filesWrongType.Add(file);            }        }        if (filesOverMaxSize.Count > 0)        {            foreach (var file in filesOverMaxSize)                FileSizeErrors?.Add($"Size error for {file.Name}");        }        if (filesWrongType.Count > 0)        {            foreach (var file in filesWrongType)                FileTypeErrors?.Add($"Type error for {file.Name}");        }        StateHasChanged();    }    catch (InvalidOperationException ex) { ErrorMessage = ex.Message; }}

The Markup:

@if (!string.IsNullOrEmpty(ErrorMessage)){<div class="alert">@ErrorMessage</div>}@foreach (string message in FileSizeErrors ?? new()){<div class="alert">@message</div>}@foreach (string message in FileTypeErrors ?? new()){<div class="alert">@message</div>}

The Test:

[Fact]public void SingleErrorShown_WhenSingleFileHasMultipleFailures(){    AddInjectedServices();    var serviceMock = new Mock<IFileValidator<FilingSettingsClient>>();    serviceMock.SetupProperty(m => m.FilingSettings, new FilingSettingsClient());    // Mock BOTH to fail    serviceMock.Setup(m => m.IsSizeValid(It.IsAny<long>(), It.IsAny<long>())).Returns(false);    serviceMock.Setup(m => m.IsTypeValid(It.IsAny<string>(), It.IsAny<string[]>())).Returns(false);    Services.AddSingleton(serviceMock.Object);    var component = Render<FileUploader>();    var fileToUpload = InputFileContent.CreateFromBinary(new byte[100], "invalid-type.exe");    // Act    component.FindComponent<InputFile>().UploadFiles(fileToUpload);    // Assert - This SHOULD fail because 2 alerts should exist, but it PASSES.    component.WaitForAssertion(() =>    {        var alerts = component.FindAll(".alert");        Assert.Equal(1, alerts.Count());     }, TimeSpan.FromSeconds(3));    serviceMock.Verify(m => m.IsTypeValid(It.IsAny<string>(), It.IsAny<string[]>()), Times.AtLeastOnce());}

Observations:

• Verify confirms both validation methods are called.

• If I change the assertion to Assert.Equal(2, alerts.Count()), the test also passes, proving the second alert eventually appears.

• It seems WaitForAssertion exits as soon as the first if block triggers a render, ignoring the subsequent state changes.

How do I ensure bUnit waits for the final render state before completing the assertion?