Where is the Visual Studio test playlist schema?

I'm running tests in Visual Studio 2017 from the Test Explorer window using the NUnit Test Adapter. I use a test playlist file which contains the tests I want to run. The contents of that file look like this:

<Playlist Version="1.0">
    <Add Test="MyAssemblyName.MyTestFixture.MyTestMethod()" />
</Playlist>

Is there a schema for these Visual Studio playlist files? If so, where is it? If not, can you provide a list here of valid XML attributes for a Playlist file (other than <Add>)?

Solution

I tried to find an XSD too, but I didn't, so I dug on Visual Studio dlls and found this one Microsoft.VisualStudio.TestWindow.Core.dll I used dnSpy to look the C# code, and I found this class PropertyRule in namespace Microsoft.VisualStudio.TestWindow.Internal.Playlists

For the property names all those are valid

PropertyRule.properties = ImmutableArray.Create<ValueTuple<string, TestPropertyType, string>>(new ValueTuple<string, TestPropertyType, string>[]
{
    new ValueTuple<string, TestPropertyType, string>("Solution", TestPropertyType.Solution, string.Empty),
    new ValueTuple<string, TestPropertyType, string>("Project", TestPropertyType.ProjectName, "TestWindow_ProjectName"),
    new ValueTuple<string, TestPropertyType, string>("Namespace", TestPropertyType.NamespaceName, "TestWindow_NamespaceName"),
    new ValueTuple<string, TestPropertyType, string>("Class", TestPropertyType.ClassName, "TestWindow_ClassName"),
    new ValueTuple<string, TestPropertyType, string>("TargetFramework", TestPropertyType.TargetFramework, "TestWindow_TargetFramework"),
    new ValueTuple<string, TestPropertyType, string>("Outcome", TestPropertyType.Outcome, "TestWindow_Outcome"),
    new ValueTuple<string, TestPropertyType, string>("Trait", TestPropertyType.Trait, "TestWindow_Traits"),
    new ValueTuple<string, TestPropertyType, string>("Test", TestPropertyType.FullyQualifiedName, "TestWindow_FullyQualifiedName"),
    new ValueTuple<string, TestPropertyType, string>("TestWithNormalizedFullyQualifiedName", TestPropertyType.NormalizedFullyQualifiedName, "TestWindow_TestGroup"),
    new ValueTuple<string, TestPropertyType, string>("DisplayName", TestPropertyType.DisplayName, "TestWindow_DisplayName")
});

Look the code for the Match attribute

using System;
    
namespace Microsoft.VisualStudio.TestWindow.Internal.Playlists
{
  [Flags]
  public enum PropertyRuleMatchFlags
  {
    Contains = 0,
    Not = 1,
    Equals = 2,
    Subset = 4
  }
}

Reading the code I was able to edit my playlist XML to ignore some project, so all others are added automatically!