Check unit test

Author: huulinhnguyen-dev

src/Build.UnitTests/BackEnd/SdkResolverLoader_Tests.cs

@@ -414,30 +414,37 @@ public void LoadResolverAssembly_MSBuildSdkResolver_WithAndWithoutFallback(bool
 
                 var assemblyFile = Path.Combine(resolverFolder, "Microsoft.DotNet.MSBuildSdkResolver.dll");
 
+                // Create file based on test scenario
                 if (shouldSucceed)
                 {
-                    // For fallback test: create a valid assembly file
-                    var sourceAssembly = typeof(SdkResolverLoader).Assembly;
-                    File.Copy(sourceAssembly.Location, assemblyFile, true);
+                    // For fallback test: copy test assembly (which is already loaded) instead of Microsoft.Build.dll
+                    // This reduces side effects because the test assembly is already in the load context
+                    var testAssembly = typeof(SdkResolverLoader_Tests).Assembly;
+                    File.Copy(testAssembly.Location, assemblyFile, true);
                 }
                 else
                 {
                     // For no-fallback test: create invalid assembly content to force Assembly.Load to fail
                     File.WriteAllText(assemblyFile, "invalid assembly content");
                 }
 
-                // Use MockSdkResolverLoader to simulate behavior without modifying global state
+                // Use MockSdkResolverLoader to test actual Assembly.LoadFrom behavior
+                // but with test assembly (already loaded) instead of Microsoft.Build.dll to reduce side effects
                 var loader = new MockSdkResolverLoader
                 {
                     FindPotentialSdkResolversFunc = (_, __) => new List<string> { assemblyFile },
+                    GetResolverTypesFunc = assembly => new[] { typeof(MockSdkResolverWithAssemblyPath) },
                     LoadResolverAssemblyFunc = (resolverPath) =>
                     {
                         string resolverFileName = Path.GetFileNameWithoutExtension(resolverPath);
                         if (resolverFileName.Equals("Microsoft.DotNet.MSBuildSdkResolver", StringComparison.OrdinalIgnoreCase))
                         {
-                            if (isRunningInVS)
+                            // Capture test parameters via closure
+                            bool simulatedIsRunningInVS = isRunningInVS;
+
+                            if (simulatedIsRunningInVS)
                             {
-                                // Simulate VS: use Assembly.Load directly, no fallback
+                                // VS behavior: try Assembly.Load directly, no fallback
                                 AssemblyName assemblyName = new AssemblyName(resolverFileName)
                                 {
                                     CodeBase = resolverPath,
@@ -447,8 +454,23 @@ public void LoadResolverAssembly_MSBuildSdkResolver_WithAndWithoutFallback(bool
                             }
                             else
                             {
-                                // Simulate non-VS: try Assembly.Load first, fallback to LoadFrom if it fails
-                                return Assembly.LoadFrom(resolverPath);
+                                // Non-VS behavior: try Assembly.Load first, fallback to LoadFrom if it fails
+                                // We actually call Assembly.LoadFrom here but with test assembly (already loaded)
+                                // to reduce side effects compared to loading Microsoft.Build.dll copy
+                                try
+                                {
+                                    // Try Assembly.Load first (will fail for invalid file, succeed for valid)
+                                    AssemblyName assemblyName = new AssemblyName(resolverFileName)
+                                    {
+                                        CodeBase = resolverPath,
+                                    };
+                                    return Assembly.Load(assemblyName);
+                                }
+                                catch (Exception)
+                                {
+                                    // Fallback to LoadFrom
+                                    return Assembly.LoadFrom(resolverPath);
+                                }
                             }
                         }
                         return Assembly.LoadFrom(resolverPath);
@@ -515,7 +537,13 @@ private sealed class MockSdkResolverWithAssemblyPath : SdkResolverBase
         {
             public string AssemblyPath;
 
-            public MockSdkResolverWithAssemblyPath(string assemblyPath = "")
+            // Parameterless constructor for reflection-based instantiation
+            public MockSdkResolverWithAssemblyPath()
+                : this("")
+            {
+            }
+
+            public MockSdkResolverWithAssemblyPath(string assemblyPath)
             {
                 AssemblyPath = assemblyPath;
             }