Unit test IStringLocalizer<T>

[jochem4207]

I've made a unit test example for IStringLocalizer. Check the comments inside

using ProjectName.Client.Pages; 
using Bunit;
using Xunit;
using FluentAssertions;
using Microsoft.Extensions.Localization;
using Microsoft.Extensions.DependencyInjection;
using ProjectName.Client.Tests.Attribute;
using AutoFixture.Xunit2;
using FakeItEasy; // Probably possible with Moq to 

namespace ProjectName.Client.Tests.Pages
{
    public class IndexTests : TestContext
    {
        [Theory]
        [AutoFakeItEasyData]
        public void IndexRendersCorrectly([Frozen] IStringLocalizer<App> localize)
        {
            Services.AddSingleton(localize);
            var welcomeKey = "Welcome";  // The key (same as in the .razor file)
            var welcomeResult = "Welkom"; // The result you want to return
            A.CallTo(() => localize[welcomeKey]).Returns(new LocalizedString(welcomeKey, welcomeResult));

            // Act
            var cut = RenderComponent<Index>();

            // Assert
            cut.Markup.Should().Contain(welcomeResult); //  Contains can be changed to anything, just my way of testing
        }
    }
}

using AutoFixture;
using AutoFixture.AutoFakeItEasy;
using AutoFixture.Xunit2;
using System;

namespace ProjectName.Client.Tests.Attribute
{
    [AttributeUsage(AttributeTargets.Method)]
    public class AutoFakeItEasyDataAttribute : AutoDataAttribute
    {
        public AutoFakeItEasyDataAttribute()
        : base(FixtureFactory)
        {
        }

        private static IFixture FixtureFactory()
        {
            return new Fixture().Customize(new AutoFakeItEasyCustomization());
        }
    }
}

The page

@page "/"
@inject IStringLocalizer<App> Localize

<h1>Hello, world!</h1>

<p>@Localize["Welcome"]</p>