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))
{
    
@ErrorMessage
}
@foreach (string message in FileSizeErrors ?? new())
{
    
@message
}
@foreach (string message in FileTypeErrors ?? new())
{
    
@message
}

The Test:

[Fact]
public void SingleErrorShown_WhenSingleFileHasMultipleFailures()
{
    AddInjectedServices();
    var serviceMock = new Mock>();
    serviceMock.SetupProperty(m => m.FilingSettings, new FilingSettingsClient());

    // Mock BOTH to fail
    serviceMock.Setup(m => m.IsSizeValid(It.IsAny(), It.IsAny())).Returns(false);
    serviceMock.Setup(m => m.IsTypeValid(It.IsAny(), It.IsAny())).Returns(false);

    Services.AddSingleton(serviceMock.Object);
    var component = Render();

    var fileToUpload = InputFileContent.CreateFromBinary(new byte[100], "invalid-type.exe");

    // Act
    component.FindComponent().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(), It.IsAny()), 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?