fix: tests

Author: maurei

src/JsonApiDotNetCore/Middleware/IncomingTypeMatchFilter.cs

@@ -37,19 +37,31 @@ public void OnActionExecuting(ActionExecutingContext context)
 
             if (request.Method == HttpMethods.Patch || request.Method == HttpMethods.Post)
             {
-                var deserializedType = context.ActionArguments.Last().Value.GetType();
-                var targetType = (_jsonApiRequest.SecondaryResource ?? _jsonApiRequest.PrimaryResource).ResourceType;
+                var deserializedType = context.ActionArguments.LastOrDefault().Value?.GetType();
+                var expectedType = GetExpectedType();
 
-                if (deserializedType != targetType)
+                if (deserializedType != null && expectedType != null && deserializedType != expectedType)
                 {
-                    ResourceContext resourceFromEndpoint = _provider.GetResourceContext(targetType);
+                    ResourceContext resourceFromEndpoint = _provider.GetResourceContext(expectedType);
                     ResourceContext resourceFromBody = _provider.GetResourceContext(deserializedType);
 
                     throw new ResourceTypeMismatchException(new HttpMethod(request.Method), request.Path, resourceFromEndpoint, resourceFromBody);
                 }
             }
         }
-        
+
+        private Type GetExpectedType()
+        {
+            if (_jsonApiRequest.Kind == EndpointKind.Primary)
+            {
+                return _jsonApiRequest.PrimaryResource?.GetType();
+            }
+            else
+            {
+                return _jsonApiRequest.SecondaryResource?.GetType();
+            }
+        }
+
         public void OnActionExecuted(ActionExecutedContext context) { /* noop */ }
     }
 }