Added/Updated JsonPatchExtensionsTest

test/Microsoft.AspNetCore.Mvc.Test/JsonPatchExtensionsTest.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Linq;
 using Microsoft.AspNetCore.JsonPatch;
 using Microsoft.AspNetCore.JsonPatch.Operations;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
@@ -46,7 +47,51 @@ namespace Microsoft.AspNetCore.Mvc
             Assert.Equal("The target location specified by path segment 'CustomerId' was not found.", error.ErrorMessage);
         }
 
-        public class Customer
+        [Fact]
+        public void ApplyTo_ValidPatchOperation_NoErrorsAdded()
+        {
+            // Arrange
+            var patch = new JsonPatchDocument<Customer>();
+            patch.Operations.Add(new Operation<Customer>("replace", "/CustomerName", null, "James"));
+            var model = new Customer();
+            var modelState = new ModelStateDictionary();
+
+            // Act
+            patch.ApplyTo(model, modelState);
+
+            // Assert
+            Assert.Equal(0, modelState.ErrorCount);
+            Assert.Equal("James", model.CustomerName);
+        }
+
+        [Theory]
+        [InlineData("test", "/CustomerName", null, "James", "The test operation is not supported.")]
+        [InlineData("invalid", "/CustomerName", null, "James", "Invalid JsonPatch operation 'invalid'.")]
+        [InlineData("", "/CustomerName", null, "James", "Invalid JsonPatch operation ''.")]
+        public void ApplyTo_InvalidPatchOperations_AddsModelStateError(
+            string op,
+            string path,
+            string from,
+            string value,
+            string error)
+        {
+            // Arrange
+            var patch = new JsonPatchDocument<Customer>();
+            patch.Operations.Add(new Operation<Customer>(op, path, from, value));
+            var model = new Customer();
+            var modelState = new ModelStateDictionary();
+
+            // Act
+            patch.ApplyTo(model, modelState);
+
+            // Assert
+            Assert.Equal(1, modelState.ErrorCount);
+            Assert.Equal(nameof(Customer), modelState.First().Key);
+            Assert.Equal(1, modelState.First().Value.Errors.Count);
+            Assert.Equal(error, modelState.First().Value.Errors.First().ErrorMessage);
+        }
+
+        private class Customer
         {
             public string CustomerName { get; set; }
         }