Complete implementation of global.json --test-runner option with valid JSON output

Co-authored-by: Youssef1313 <[email protected]>

Author: Copilot

template_feed/Microsoft.DotNet.Common.ItemTemplates/content/GlobalJson/global.json

@@ -4,10 +4,12 @@
     "rollForward": "ROLL_FORWARD_VALUE",
     //#endif
     "version": "SDK_VERSION"
-  }//#if (TestRunner!="")
-,
+  }
+  //#if (TestRunner=="")
+  //#else
+  ,
   "test": {
     "runner": "TEST_RUNNER_VALUE"
   }
-//#endif
+  //#endif
 }

test/dotnet-new.IntegrationTests/CommonTemplatesTests.cs

@@ -29,9 +29,15 @@ public CommonTemplatesTests(SharedHomeDirectory fixture, ITestOutputHelper log)
         [InlineData("global.json file", "globaljson", null)]
         [InlineData("global.json file", "globaljson", new[] { "--sdk-version", "6.0.200" })]
         [InlineData("global.json file", "globaljson", new[] { "--sdk-version", "6.0.200", "--roll-forward", "major" })]
+        [InlineData("global.json file", "globaljson", new[] { "--TestRunner", "VSTest" })]
+        [InlineData("global.json file", "globaljson", new[] { "--TestRunner", "Microsoft.Testing.Platform" })]
+        [InlineData("global.json file", "globaljson", new[] { "--sdk-version", "6.0.200", "--TestRunner", "VSTest" })]
+        [InlineData("global.json file", "globaljson", new[] { "--roll-forward", "major", "--TestRunner", "Microsoft.Testing.Platform" })]
         [InlineData("global.json file", "global.json", null)]
         [InlineData("global.json file", "global.json", new[] { "--sdk-version", "6.0.200" })]
         [InlineData("global.json file", "global.json", new[] { "--sdk-version", "6.0.200", "--roll-forward", "major" })]
+        [InlineData("global.json file", "global.json", new[] { "--TestRunner", "VSTest" })]
+        [InlineData("global.json file", "global.json", new[] { "--TestRunner", "Microsoft.Testing.Platform" })]
         [InlineData("NuGet Config", "nugetconfig", null)]
         [InlineData("NuGet Config", "nuget.config", null)]
         [InlineData("dotnet gitignore file", "gitignore", null)]