fix: when setting any content header after setting the HttpContent wi…

…th JsonBody (or any other custom IResponseBehavior) it would reset the HttpContent to an empty content. (#99)

src/MockHttp/Language/Flow/Response/EnsureHttpContentBehavior.cs

@@ -0,0 +1,19 @@
+using MockHttp.Responses;
+
+namespace MockHttp.Language.Flow.Response;
+
+internal sealed class EnsureHttpContentBehavior
+    : IResponseBehavior
+{
+    public Task HandleAsync
+    (
+        MockHttpRequestContext requestContext,
+        HttpResponseMessage responseMessage,
+        ResponseHandlerDelegate next,
+        CancellationToken cancellationToken)
+    {
+        // ReSharper disable once NullCoalescingConditionIsAlwaysNotNullAccordingToAPIContract
+        responseMessage.Content ??= new EmptyContent();
+        return next(requestContext, responseMessage, cancellationToken);
+    }
+}

src/MockHttp/Language/Flow/Response/ResponseBuilder.cs

@@ -12,10 +12,12 @@ internal sealed class ResponseBuilder
       IWithContentResult,
       IWithHeadersResult
 {
-    private static readonly Func<CancellationToken, Task<HttpContent>> EmptyHttpContentFactory = _ => Task.FromResult<HttpContent>(new EmptyContent());
-
     /// <inheritdoc />
-    public IList<IResponseBehavior> Behaviors { get; } = new List<IResponseBehavior>();
+    public IList<IResponseBehavior> Behaviors { get; } = new List<IResponseBehavior>
+    {
+        // We're adding this default behavior as the first step, to ensure HttpContent is not null initially.
+        new EnsureHttpContentBehavior()
+    };
 
     /// <inheritdoc />
     public IWithStatusCodeResult StatusCode(HttpStatusCode statusCode, string? reasonPhrase = null)
@@ -56,12 +58,6 @@ public IWithHeadersResult Headers(IEnumerable<KeyValuePair<string, IEnumerable<s
             throw new ArgumentException("At least one header must be specified.", nameof(headers));
         }
 
-        // If no content when adding headers, we force empty content so that content headers can still be set.
-        if (!Behaviors.OfType<HttpContentBehavior>().Any())
-        {
-            Body(EmptyHttpContentFactory);
-        }
-
         Behaviors.Add(new HttpHeaderBehavior(headerList));
         return this;
     }
@@ -157,4 +153,3 @@ int CompareOtherWayAround(int result)
         }
     }
 }
-

test/MockHttp.Json.Tests/Issues/Issue98.cs

@@ -0,0 +1,45 @@
+using System.Net;
+using System.Text;
+using MockHttp.FluentAssertions;
+using Newtonsoft.Json;
+
+namespace MockHttp.Json.Issues;
+
+public class Issue98
+{
+    [Fact]
+    public async Task When_setting_content_header_after_setting_jsonBody_it_should_return_expected_response()
+    {
+        using var mockHttp = new MockHttpHandler();
+        mockHttp
+            .When(m => m
+                .Method(HttpMethod.Post)
+                .RequestUri("api/login")
+                .ContentType("application/json; charset=utf-8")
+                .JsonBody(new { username = @"corp\user", password = "Super.Mari0.Bro$$" })
+            )
+            .Respond(r => r
+                .StatusCode(HttpStatusCode.OK)
+                .JsonBody(new { username = "user@corp" }, Encoding.UTF8)
+                .Header("Set-Cookie",
+                    "session=abcdefghi==; Expires=Tue, 01 Feb 2024 01:01:01 GMT; Secure; HttpOnly; Path=/")
+            )
+            .Verifiable();
+
+        var client = new HttpClient(mockHttp)
+        {
+            BaseAddress = new Uri("http://localhost")
+        };
+        // Act
+        HttpResponseMessage? response = await client.PostAsJsonAsync("api/login", new { username = @"corp\user", password = @"Super.Mari0.Bro$$" });
+
+        // Assert
+        response.Should().HaveStatusCode(HttpStatusCode.OK);
+        response.Headers.Should()
+            .ContainKey("Set-Cookie",
+                "session=abcdefghi==; Expires=Tue, 01 Feb 2024 01:01:01 GMT; Secure; HttpOnly; Path=/");
+        response.Should().HaveContentType("application/json; charset=utf-8");
+        await response.Should().HaveContentAsync(JsonConvert.SerializeObject(new { username = "user@corp" }), Encoding.UTF8);
+        mockHttp.Verify();
+    }
+}