Fix NullReferenceException in test mock creation

Updated CreateMockExternalLink to handle cases where RegisteredLinkType constructors may have changed. The method now tries multiple constructor signatures and provides better error handling when reflection fails to find a suitable constructor.

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

Author: Copilot

src/MigrationTools.Clients.TfsObjectModel.Tests/Tools/TfsGitRepositoryInfoTests.cs

@@ -16,14 +16,58 @@ public class TfsGitRepositoryInfoTests
         /// </summary>
         private ExternalLink CreateMockExternalLink(string uri)
         {
-            // Create a mock RegisteredLinkType using reflection
+            // Try to create a mock RegisteredLinkType using reflection
+            // First try the two-parameter constructor
             var linkTypeConstructor = typeof(RegisteredLinkType).GetConstructor(
                 BindingFlags.NonPublic | BindingFlags.Instance,
                 null,
                 new Type[] { typeof(string), typeof(string) },
                 null);
 
-            var linkType = (RegisteredLinkType)linkTypeConstructor.Invoke(new object[] { "MockLinkType", "Mock Link Type" });
+            RegisteredLinkType linkType = null;
+            
+            if (linkTypeConstructor != null)
+            {
+                linkType = (RegisteredLinkType)linkTypeConstructor.Invoke(new object[] { "MockLinkType", "Mock Link Type" });
+            }
+            else
+            {
+                // Try alternative constructors if the two-parameter one doesn't exist
+                var constructors = typeof(RegisteredLinkType).GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public);
+                
+                foreach (var ctor in constructors)
+                {
+                    var parameters = ctor.GetParameters();
+                    if (parameters.Length == 1 && parameters[0].ParameterType == typeof(string))
+                    {
+                        linkType = (RegisteredLinkType)ctor.Invoke(new object[] { "MockLinkType" });
+                        break;
+                    }
+                    else if (parameters.Length == 0)
+                    {
+                        linkType = (RegisteredLinkType)ctor.Invoke(new object[] { });
+                        break;
+                    }
+                }
+                
+                // If still null, try to find any constructor with minimal parameters
+                if (linkType == null && constructors.Length > 0)
+                {
+                    var simplestCtor = constructors[0];
+                    var ctorParams = simplestCtor.GetParameters();
+                    var args = new object[ctorParams.Length];
+                    for (int i = 0; i < ctorParams.Length; i++)
+                    {
+                        args[i] = ctorParams[i].ParameterType.IsValueType ? Activator.CreateInstance(ctorParams[i].ParameterType) : null;
+                    }
+                    linkType = (RegisteredLinkType)simplestCtor.Invoke(args);
+                }
+            }
+
+            if (linkType == null)
+            {
+                throw new InvalidOperationException("Could not create RegisteredLinkType instance via reflection. Available constructors may have changed.");
+            }
 
             // Create ExternalLink using the mock link type
             return new ExternalLink(linkType, uri);