Fix #2793: Use proper FQN in VS Test Explorer to avoid hierarchy split (#2978)

When job display name contains '.' (e.g., '.NET 8.0.6'), VS Test Explorer
interprets it as a namespace separator, causing incorrect hierarchy grouping.

Detect Visual Studio environment via VSAPPIDNAME env variable and use
the benchmark method FQN instead of displayName for the test case.

Co-authored-by: Shrinidhi203 <[email protected]>

Author: Shrinidhi203

src/BenchmarkDotNet.TestAdapter/BenchmarkCaseExtensions.cs

@@ -35,6 +35,15 @@ internal static TestCase ToVsTestCase(this BenchmarkCase benchmarkCase, string a
             // See: https://github.com/dotnet/BenchmarkDotNet/issues/2494
             var fullyQualifiedName = displayName;
 
+            // Use benchmark method FQN on Visual Studio environment to avoid TestExplorer hierarchy split
+            // when job display name contains '.' which is interpreted as a namespace separator by VS.
+            // See: https://github.com/dotnet/BenchmarkDotNet/issues/2793
+            if (Environment.GetEnvironmentVariable("VSAPPIDNAME") != null)
+            {
+                var benchmarkMethodName = benchmarkMethod.Name;
+                fullyQualifiedName = $"{fullClassName}.{benchmarkMethodName}";
+            }
+
             var vsTestCase = new TestCase(fullyQualifiedName, VsTestAdapter.ExecutorUri, assemblyPath)
             {
                 DisplayName = displayName,