Only verify VS 18 major version in tests (#1281)

Author: lbussell

manifest.versions.json

@@ -13,7 +13,7 @@
     "referenceassemblies|version": "1.0.3",
     "servicemonitor|version": "2.0.1.10",
     "servicemonitor|url": "https://github.com/microsoft/IIS.ServiceMonitor/releases/download/v$(servicemonitor|version)/ServiceMonitor.exe",
-    "vs|version": "18.0",
+    "vs|version": "18",
     "vs|buildToolsUrl": "https://aka.ms/vs/stable/vs_BuildTools.exe",
     "vs|ltsc2016|version": "17.14",
     "vs|ltsc2016|testAgentUrl": "https://aka.ms/vs/17/release/vs_TestAgent.exe",

tests/Microsoft.DotNet.Framework.Docker.Tests/ImageDescriptorExtensions.cs

@@ -30,7 +30,16 @@ public static Version GetExpectedVsVersion(this ImageDescriptor imageDescriptor)
             _ =>                      "vs|version",
         };
 
-        return Version.Parse((string)manifestVariables[vsVersionVariable]);
+        string versionString = (string)manifestVariables[vsVersionVariable];
+
+        // Version.Parse requires at least major.minor format.
+        // If the version string is just a single number, append ".0".
+        if (!versionString.Contains('.'))
+        {
+            versionString += ".0";
+        }
+
+        return Version.Parse(versionString);
     }
 
     /// <summary>

tests/Microsoft.DotNet.Framework.Docker.Tests/SdkOnlyImageTests.cs

@@ -114,8 +114,14 @@ public void VerifyVsWhereOperability(ImageDescriptor imageDescriptor)
             Version actualVsVersion = Version.Parse(json[0]["catalog"]["buildVersion"].ToString());
             Version expectedVsVersion = imageDescriptor.GetExpectedVsVersion();
 
+            // For VS 18 and later, only verify the major version since new minor versions release monthly.
+            // See https://learn.microsoft.com/visualstudio/releases/2026/release-notes#december-update-1810
             Assert.Equal(expectedVsVersion.Major, actualVsVersion.Major);
-            Assert.Equal(expectedVsVersion.Minor, actualVsVersion.Minor);
+            // For VS versions < 18, continue to verify the minor version.
+            if (expectedVsVersion.Major < 18 || actualVsVersion.Major < 18)
+            {
+                Assert.Equal(expectedVsVersion.Minor, actualVsVersion.Minor);
+            }
         }
 
         [SkippableTheory]