Skip h2spec test enumeration on unsupported platforms dotnet#38794 (dotnet#38799)

Author: Tratcher

src/Servers/Kestrel/test/Interop.FunctionalTests/H2SpecCommands.cs

@@ -45,12 +45,18 @@ public static class H2SpecCommands
 
     private static string GetToolLocation()
     {
+        if (RuntimeInformation.OSArchitecture != Architecture.X64)
+        {
+            // This is a known, unsupported scenario, no-op.
+            return null;
+        }
+
         var root = Path.Combine(Environment.CurrentDirectory, "h2spec");
         if (OperatingSystem.IsWindows())
         {
             return Path.Combine(root, "windows", "h2spec.exe");
         }
-        else if (OperatingSystem.IsLinux() && (RuntimeInformation.OSArchitecture == Architecture.X64))
+        else if (OperatingSystem.IsLinux())
         {
             var toolPath = Path.Combine(root, "linux", "h2spec");
             chmod755(toolPath);
@@ -67,10 +73,17 @@ private static string GetToolLocation()
 
     public static IList<Tuple<string, string>> EnumerateTestCases()
     {
+        // The tool isn't supported on some platforms (arm64), so we can't even enumerate the tests.
+        var toolLocation = GetToolLocation();
+        if (toolLocation == null)
+        {
+            return null;
+        }
+
         var testCases = new List<Tuple<string, string>>();
         var processOptions = new ProcessStartInfo
         {
-            FileName = GetToolLocation(),
+            FileName = toolLocation,
             RedirectStandardOutput = true,
             Arguments = "--strict --dryrun",
             WindowStyle = ProcessWindowStyle.Hidden,

src/Servers/Kestrel/test/Interop.FunctionalTests/H2SpecTests.cs

@@ -63,9 +63,20 @@ public static TheoryData<H2SpecTestCase> H2SpecTestCases
             var dataset = new TheoryData<H2SpecTestCase>();
             var toSkip = new string[] { "http2/6.9.1/2" };
 
+            var testCases = H2SpecCommands.EnumerateTestCases();
+
+            if (testCases == null || !testCases.Any())
+            {
+                dataset.Add(new H2SpecTestCase()
+                {
+                    Skip = "Unable to detect test cases on this platform.",
+                });
+                return dataset;
+            }
+
             var supportsAlpn = Utilities.CurrentPlatformSupportsHTTP2OverTls();
 
-            foreach (var testcase in H2SpecCommands.EnumerateTestCases())
+            foreach (var testcase in testCases)
             {
                 string skip = null;
                 if (toSkip.Contains(testcase.Item1))