Value cannot be null, Parameter 'jsObjectReference' when using AspNetCore Title component

[dawidr]

I've a problem writing test for a page which is using Microsoft.AspNetCore.Components.Web.Extensions.Head.Title component.
No issues when I remove the Title. The page looks like this:

@page "/sample"

<Title Value="Sample"></Title>

<div>@Text</div>

@code {
    [Parameter]
    public string Text { get; set; } = string.Empty;
}

And here is the test:

using Bunit;
using Bunit.TestDoubles;
using Xunit;

namespace Tests
{
    public class SampleTests
    {
        private TestContext _context;

        public SampleTests()
        {
            _context = new TestContext();
            _context.Services.AddMockJSRuntime();
        }

        [Fact]
        public void PageShouldRender()
        {
            var html = _context.RenderComponent<Sample>(parameters =>
                parameters.Add(p => p.Text, "Sample"));
        }

    }
}

Error:
{"Value cannot be null. (Parameter 'jsObjectReference')"}

[egil]

Hi @dawidr

Please provide the following info:

• bUnit library version:
• .NET Core/Blazor version:

[dawidr]

@egil After your comment, I noticed that I've outdated bUnit. So right now I'm on bUnit 1.0.0-preview-01 and .Net Core 5.0.1.
I removed line _context.Services.AddMockJSRuntime(); as it is obsolete.

The error is different right now:

Bunit.JSRuntimeUnhandledInvocationException: 'The invocation of 'import' with the argument [./_content/Microsoft.AspNetCore.Components.Web.Extensions/headManager.js] was not expected.'

To put more light on the <Title> component. It requires <script src="_content/Microsoft.AspNetCore.Components.Web.Extensions/headManager.js"></script> in the layout file.

[egil]

The alternative to the previous suggestion is to setup handling of the headManager.js module explicitly. Something like this should work:

var headManagerModule = _context.JSInterop.SetupModule("./_content/Microsoft.AspNetCore.Components.Web.Extensions/headManager.js");
headManagerModule.Mode = JSRuntimeMode.Loose;

[egil]

Try settting JSRuntimeMode to Loose, see here for more details: https://bunit.egilhansen.com/docs/test-doubles/emulating-ijsruntime.html