How to execute method on component?

[robalexclark]

What is the correct way to execute a method on a component? For example I have a MessageBox component, which builds on the Blazorise Modal dialog.

@code {
    private string title;
    private string message;

    // reference to the modal component
    private Modal messageBoxModal;

    public void ShowMessageBox(string title, string message)
    {
        this.title = title;
        this.message = message;

        messageBoxModal.Show();
    }

    private void CloseMessageBox()
    {
        messageBoxModal.Hide();
    }
}

I'm trying to test "ShowMessageBox" as follows:

....
            var mb = cut.Instance;
            mb.ShowMessageBox("Test Title", "Test message");

But this results in the following error:
'The current thread is not associated with the Dispatcher. Use InvokeAsync() to switch execution to the Dispatcher when triggering rendering or component state.'

Is this a issue with the way I am testing, the bUnit library or the fact that the Blazorise modal probably uses some fancy async / Invoke methodology?

[egil]

@robalexclark good question.

Right now with beta-6, you can do the following (I think, not tested):

public void Test()
{
    var cut = RenderComponent<MessageBox>();
    
    Renderer.Dispatcher.InvokeAsync(() => cut.Instance.ShowMessageBox("Test Title", "Test message"));

    // ... do assertions
}

Alternatively, I think you can change your component to do the following:

    public void ShowMessageBox(string title, string message)
    {
        this.title = title;
        this.message = message;
        InvokeAsync(() => messageBoxModal.Show());
    }

A little background: The reason this problem shows up is because the renderer, which re-renders the component when you ShowMessageBox, runs on a different thread than the test runs. The same problem can occur in a production environment, e.g. if you have a timer that triggers something in a component. Here is a bit more background on this: https://cloudscopeph.com/blazor-exception-current-thread-is-not-associated-with-the-renderers-synchronization-context/

In a future version of the library, I think it would be a good idea to add the InvokeAsync method to e.g. the test context you are executing the tests in, making it easier to do what I show in the test example above.

If this solves the problem, please let me know and close the issue if you are happy with the solution.

[robalexclark]

Renderer.Dispatcher.InvokeAsync does resolve the issue - thank you.