Migrate Unit Tests to Xunit

[TheCodeTraveler]

Description

Migrating to Xunit is the first step towards adding Device Tests to the MAUI Community Toolkit.

To run Device Tests, XHarness is required, which uses Xunit. Writing both device and non-device unit tests with Xunit also allows us to re-use code between the testing projects.

Note: There is a known-issue with using dotnet test with a Unit Test that also includes `true in its csproj. The .NET MAUI team is aware of this and are targeting a fix for .NET MAUI Preview 10 in November.

Details

• Remove NUnit NuGet Package
• Add xunit NuGet Package
• Convert NUnit attributes to xunit attributes, e.g. [Test] -> [Fact]
• Remove Directory.Build.targets
  • This was causing an error because testhost.runtimeconfig.json was not included in the bin output
  • Directory.Build.targets was only necessary in earlier previews of .NET MAUI

[TheCodeTraveler]

@jfversluis Could you take a look at why the PR Feed is failing?

[pictos]

I've just two comments here, but I think that doesn't block this PR

[pictos]

This is something that I'm not 100% sure about, should we call this method just if we implement the destructor (`~ BaseTest() {}`)?

[TheCodeTraveler]

I added IDisposible because it is recommended by Xunit as the replacement for [TearDown] in Nunit:
https://xunit.net/docs/comparisons

[TheCodeTraveler]

Other tests that also want to include [TearDown] code can override protected virtual void Dispose(bool isDisposing)

public class ExampleTest : BaseTest
{
    [Fact]
    public void ExampleTest()
    {
      // Test code
    }

    protected override void Dispose(bool isDisposing)
    {
        // Teardown test
        base.Dispose(isDisposing);
    }
}

[pictos]

I'm sorry, I was talking about the GC.SuppressFinalize(this); It's fine to implement the Dispose method without that GC method, I guess. As I mentioned I need to review the pattern, but this shouldn't be a blocker anyway.

[TheCodeTraveler]

Ah - gotchya.

Yea, GC.SupressFinalize was new to me too!

I found it recommended in the docs: https://docs.microsoft.com/en-us/dotnet/standard/garbage-collection/implementing-dispose#the-dispose-method

[jfversluis]

@jfversluis Could you take a look at why the PR Feed is failing?

This one should be fixed from here on out!

[pictos]

LGTM!