Add WithBody(object) overload to RequestMockBuilder for JSON body matching

Mockly.ApiVerificationTests/ApprovedApi/net47.verified.txt

@@ -104,6 +104,7 @@ namespace Mockly.Http
         public Mockly.Http.RequestMockBuilder Twice() { }
         public Mockly.Http.RequestMockBuilder With(System.Func<Mockly.Http.RequestInfo, System.Threading.Tasks.Task<bool>> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
         public Mockly.Http.RequestMockBuilder With(System.Func<Mockly.Http.RequestInfo, bool> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
+        public Mockly.Http.RequestMockBuilder WithBody(object body) { }
         public Mockly.Http.RequestMockBuilder WithBody(string wildcardPattern) { }
         public Mockly.Http.RequestMockBuilder WithBodyMatchingJson(string json) { }
         public Mockly.Http.RequestMockBuilder WithBodyMatchingRegex(string regex) { }

Mockly.ApiVerificationTests/ApprovedApi/net472.verified.txt

@@ -129,6 +129,7 @@ namespace Mockly
         public Mockly.RequestMockBuilder With(System.Func<Mockly.RequestInfo, System.Threading.Tasks.Task<bool>> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
         public Mockly.RequestMockBuilder With(System.Func<Mockly.RequestInfo, bool> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
         public Mockly.RequestMockBuilder WithAnyQuery() { }
+        public Mockly.RequestMockBuilder WithBody(object body) { }
         public Mockly.RequestMockBuilder WithBody(string wildcardPattern) { }
         public Mockly.RequestMockBuilder WithBodyMatchingJson(string json) { }
         public Mockly.RequestMockBuilder WithBodyMatchingRegex(string regex) { }

Mockly.ApiVerificationTests/ApprovedApi/net8.0.verified.txt

@@ -132,6 +132,7 @@ namespace Mockly
         public Mockly.RequestMockBuilder With(System.Func<Mockly.RequestInfo, System.Threading.Tasks.Task<bool>> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
         public Mockly.RequestMockBuilder With(System.Func<Mockly.RequestInfo, bool> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
         public Mockly.RequestMockBuilder WithAnyQuery() { }
+        public Mockly.RequestMockBuilder WithBody(object body) { }
         public Mockly.RequestMockBuilder WithBody(string wildcardPattern) { }
         public Mockly.RequestMockBuilder WithBodyMatchingJson(string json) { }
         public Mockly.RequestMockBuilder WithBodyMatchingRegex([System.Diagnostics.CodeAnalysis.StringSyntax("Regex")] string regex) { }

Mockly.ApiVerificationTests/ApprovedApi/netstandard2.0.verified.txt

@@ -104,6 +104,7 @@ namespace Mockly.Http
         public Mockly.Http.RequestMockBuilder Twice() { }
         public Mockly.Http.RequestMockBuilder With(System.Func<Mockly.Http.RequestInfo, System.Threading.Tasks.Task<bool>> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
         public Mockly.Http.RequestMockBuilder With(System.Func<Mockly.Http.RequestInfo, bool> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
+        public Mockly.Http.RequestMockBuilder WithBody(object body) { }
         public Mockly.Http.RequestMockBuilder WithBody(string wildcardPattern) { }
         public Mockly.Http.RequestMockBuilder WithBodyMatchingJson(string json) { }
         public Mockly.Http.RequestMockBuilder WithBodyMatchingRegex(string regex) { }

Mockly.ApiVerificationTests/ApprovedApi/netstandard2.1.verified.txt

@@ -104,6 +104,7 @@ namespace Mockly.Http
         public Mockly.Http.RequestMockBuilder Twice() { }
         public Mockly.Http.RequestMockBuilder With(System.Func<Mockly.Http.RequestInfo, System.Threading.Tasks.Task<bool>> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
         public Mockly.Http.RequestMockBuilder With(System.Func<Mockly.Http.RequestInfo, bool> matcher, [System.Runtime.CompilerServices.CallerArgumentExpression("matcher")] string? matcherText = null) { }
+        public Mockly.Http.RequestMockBuilder WithBody(object body) { }
         public Mockly.Http.RequestMockBuilder WithBody(string wildcardPattern) { }
         public Mockly.Http.RequestMockBuilder WithBodyMatchingJson(string json) { }
         public Mockly.Http.RequestMockBuilder WithBodyMatchingRegex(string regex) { }

Mockly.Specs/HttpMockSpecs.cs

@@ -605,6 +605,55 @@ await act.Should().ThrowAsync<RequestMatchingException>().WithMessage(
                 "Could not parse the request body as JSON*");
         }
 
+        [Fact]
+        public async Task Can_match_the_body_against_a_serialized_object()
+        {
+            // Arrange
+            var mock = new HttpMock();
+
+            mock.ForPost()
+                .WithPath("/api/json")
+                .WithBody(new { name = "John", age = 30 })
+                .RespondsWithStatus(HttpStatusCode.NoContent);
+
+            var client = mock.GetClient();
+
+            // Act
+            var response = await client.PostAsync("https://localhost/api/json", new StringContent(
+                """
+                {
+                "name" : "John",
+                "age" : 30
+                }
+
+                """));
+
+            // Assert
+            response.StatusCode.Should().Be(HttpStatusCode.NoContent);
+        }
+
+        [Fact]
+        public async Task Will_report_the_expected_json_for_serialized_object()
+        {
+            // Arrange
+            var mock = new HttpMock();
+
+            mock.ForPost()
+                .WithPath("/api/json")
+                .WithBody(new { name = "John", age = 30 })
+                .RespondsWithStatus(HttpStatusCode.NoContent);
+
+            var client = mock.GetClient();
+
+            // Act
+            var action = async () => await client.PostAsync("https://localhost/api/json",
+                new StringContent("{\"name\": \"Jane\", \"age\": 25}"));
+
+            // Assert
+            await action.Should().ThrowAsync<UnexpectedRequestException>()
+                .WithMessage("*body matches JSON*\"name\"*\"John\"*");
+        }
+
         [Fact]
         public async Task Can_match_body_against_a_regex_pattern()
         {

Mockly/RequestMockBuilder.cs

@@ -177,6 +177,27 @@ public RequestMockBuilder WithBodyMatchingJson(string json)
             }, $"body matches JSON {json}");
     }
 
+    /// <summary>
+    /// Configures the request mock to match requests whose body contains the JSON equivalent to the specified object,
+    /// serialized using <see cref="JsonSerializer"/>, ignoring differences in whitespace and layout.
+    /// </summary>
+    /// <param name="body">The object to serialize to JSON and compare against the request body.</param>
+    /// <remarks>
+    /// The <paramref name="body"/> is serialized using <see cref="JsonSerializer.Serialize(object?, System.Type, JsonSerializerOptions?)"/>
+    /// with the default <see cref="JsonSerializerOptions"/>. The comparison is then performed by comparing the serialized JSON
+    /// with the request body using JSON equivalence, ignoring differences in whitespace and layout.
+    /// </remarks>
+    public RequestMockBuilder WithBody(object body)
+    {
+        if (body is null)
+        {
+            throw new ArgumentNullException(nameof(body));
+        }
+
+        var json = JsonSerializer.Serialize(body);
+        return WithBodyMatchingJson(json);
+    }
+
     /// <summary>
     /// Configures the request mock to match requests whose body content satisfies the specified wildcard pattern.
     /// </summary>

website/docs/advanced.md

@@ -58,7 +58,7 @@ mock.ForPost()
 
 ### JSON Equivalence
 
-Layout and whitespace independent:
+Layout and whitespace independent, using a raw JSON string:
 
 ```csharp
 mock.ForPost()
@@ -71,6 +71,23 @@ mock.ForPost()
 If the body cannot be parsed as JSON for `WithBodyMatchingJson`, a `RequestMatchingException` is thrown.
 :::
 
+### Object Serialized to JSON
+
+Pass an object directly and let Mockly serialize it to JSON for matching. This is useful when you have a strongly-typed request body:
+
+```csharp
+mock.ForPatch()
+    .WithPath("/api/relationships/42")
+    .WithBody(new
+    {
+        EntityKey = "TheRuleKey",
+        RepresentativeId = "abc123"
+    })
+    .RespondsWithStatus(HttpStatusCode.NoContent);
+```
+
+The object is serialized using `JsonSerializer` with default options and compared to the request body using JSON equivalence, ignoring differences in whitespace and layout.
+
 ### Regular Expression
 
 ```csharp