[ProjectTemplates/SolutionTemplates][Testing] Add xUnit Testing Project to options for Wizard to include in new Uno Apps

[DevTKSS]

What would you like to be added:

xUnit is commonly preffered for .Net 6+, provides parralel testing by default, uses DI better and avoides static Methods for Tests. Additionally the test runtime is shorter because it requires less Setup and Cleanup.

Why is this needed:

From Wizard its only possible to choose NUnit for testing in Uno Projects

For which Platform:

• iOS
• Android
• WebAssembly
• WebAssembly renders for Xamarin.Forms
• Windows
• Build tasks

Anything else we need to know?

[DevTKSS]

this here I would propose this:

optional just provide a option that would execute a dotnet new xunit --output Tests with maybe required prefix, for the solution structure

Diff comparison against a NUnit Test we are currently getting as option:

.csproj File

    <ItemGroup>
-      <PackageReference Include="FluentAssertions" /> // !!!
        <PackageReference Include="Microsoft.NET.Test.Sdk" />
-      <PackageReference Include="NUnit" />
-      <PackageReference Include="NUnit3TestAdapter" />
+     <PackageReference Include="xunit" />
+      <PackageReference Include="xunit.runner.visualstudio">
+          <PrivateAssets>all</PrivateAssets>
+         <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+       </PackageReference>
-      <PackageReference Include="coverlet.collector" />
  </ItemGroup>

Removed the coverlet.collector as I do not see by nature a requirement for this to have included. If there is any, please let me know!

For the Removement of FluentAssertions please see this Idea Discussion on the Uno Repository
I do not want to sue a not payed License Right, by unpurposely having it upgraded to latest, so would same time vote this up to let us opt into this on purpose especially when using the CI/CD pipeline options on the templates!

AppInfoTests.cs File

public class AppInfoTests
{
-    [SetUp]
-    public void Setup()
-    {
-    }

-    [Test]
+   [Fact]
-    public void AppInfoCreation()
+   public void AppInfo_ShouldNotBeNull_AfterCreation() // renaming to follow common test naming standards
    {
        var appInfo = new AppConfig { Environment = "Test" };

-        appInfo.Should().NotBeNull();
+       Assert.NotNull(appInfo);
-        appInfo.Environment.Should().Be("Test");
+       Assert.Equal("Test",appInfo.Environment);
    }
}

GlobalUsings.cs

- global using NUnit;
+ global using Xunit;