bUnit test a component that has a TelerikDropZone

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DropZone General Discussions
Jeremy
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Jeremy asked on 30 Nov 2023, 08:53 PM | edited on 30 Nov 2023, 08:55 PM
Hi,

I am trying to test a component that has a 'TelerikDropZone' inside, I don't need to do any interaction with the drop zone but when I try to render my component (using bUnit)
var myCmp = RenderComponent<MyComponent>();
It gives an error


System.NullReferenceException: Object reference not set to an instance of an object.

System.NullReferenceException
Object reference not set to an instance of an object.
   at Telerik.Blazor.Components.TelerikDropZone..ctor()
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean wrapExceptions)
As best I can tell looking at it, it seems to be coming up from the 'BaseComponent.Localizer'
[Parameter]
    public string HintText { get; set; } = BaseComponent.Localizer["DropZone_Hint"];


And if I just comment out the TelerikDropZone my tests run fine.

DropZone definition if it helps -

<TelerikDropZone Id="myDz">
                <Template>
                    <div class="hint">
                        <i class="far fa-file-plus me-2"></i>
                        <span>
                            Drag and drop file here
                        </span>
                    </div>
                </Template>
            </TelerikDropZone>

Is there some extra setup I need to do here in order to get it to work?

Thanks!

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Dimo
Telerik team
answered on 05 Dec 2023, 10:04 AM

Hello Jeremy,

All our components render UI labels with an ITelerikStringLocalizer, which is initialized in BaseComponent.OnInitializedAsync. Our components use a localization service for consistency even when there is no true localization in the app.

Here is how the BaseComponent localizer is assigned.

(InitLocalizer() is called in OnInitializedAsync)

        protected void InitLocalizer()
        {
            if (Localizer == null)
            {
                var injectedLocalizer = ServiceProvider?.GetService(typeof(ITelerikStringLocalizer)) as ITelerikStringLocalizer;

                if (injectedLocalizer != null) // depends on builder.Services.AddTelerikBlazor(); in Program.cs
                {
                    Localizer = injectedLocalizer;
                }
                else if (RootComponent?.Localizer != null) // depends on <TelerikRootComponent Localizer="..." />
                {
                    Localizer = RootComponent?.Localizer;
                }
                else
                {
                    Localizer = new TelerikStringLocalizer();
                }
            }
        }

 

So, the Localizer should not be null, unless OnInitializedAsync is not executed at all. I am not familiar with the bUnit's internals and how is this even possible. There is a bUnit documentation on a related topic. You can also try setting the HintText parameter explicitly as a workaround, but normally, this shouldn't be necessary and we don't set localization-dependent parameters in our bUnit sample.

Regards,
Dimo
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Jeremy
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commented on 08 Dec 2023, 04:07 PM

Thanks Dimo you are a life-saver!

I "borrowed" the 'TelerikTestContext' here and had my tests inherit from it instead of plain 'TestContext' and that fixed the problem.

I think it was down to the overrides for 'Render'/'RenderComponent' ensuring the 'TelerikRootComponent' is setup when rendering.
Dimo
Telerik team
commented on 08 Dec 2023, 04:33 PM

Yes, that file also creates a localizer. I am glad it works now.
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Dimo
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