Fixing location header not respecting custom value

src/Teapot.Web.Tests/IntegrationTests/CustomHeaderTests.cs

@@ -1,22 +1,35 @@
 using Microsoft.AspNetCore.Mvc.Testing;
+using System.Net.Http;
 
 namespace Teapot.Web.Tests.IntegrationTests;
 
 public class CustomHeaderTests
 {
+    [OneTimeSetUp]
+    public void OneTimeSetUp()
+    {
+        _httpClient = new WebApplicationFactory<Program>().CreateDefaultClient();
+    }
+
+    [OneTimeTearDown]
+    public void OneTimeTearDown()
+    {
+        _httpClient.Dispose();
+    }
+
+    private HttpClient _httpClient = null!;
 
     [Test]
     public async Task CanSetCustomHeaders()
     {
-        HttpClient httpClient = new WebApplicationFactory<Program>().CreateDefaultClient();
         string uri = "/200";
         string headerName = "Foo";
         string headerValue = "bar";
 
         using HttpRequestMessage request = new(HttpMethod.Get, uri);
         request.Headers.Add($"{StatusExtensions.CUSTOM_RESPONSE_HEADER_PREFIX}{headerName}", headerValue);
 
-        using HttpResponseMessage response = await httpClient.SendAsync(request);
+        using HttpResponseMessage response = await _httpClient.SendAsync(request);
 
         System.Net.Http.Headers.HttpResponseHeaders headers = response.Headers;
         Assert.Multiple(() =>
@@ -28,4 +41,27 @@ public async Task CanSetCustomHeaders()
             Assert.That(values!.First(), Is.EqualTo(headerValue));
         });
     }
+
+    [Test]
+    public async Task Redirects302ToCorrectLocation()
+    {
+        string uri = "/302";
+        string headerName = "Location";
+        string headerValue = "example.com";
+
+        using HttpRequestMessage request = new(HttpMethod.Get, uri);
+        request.Headers.Add($"{StatusExtensions.CUSTOM_RESPONSE_HEADER_PREFIX}{headerName}", headerValue);
+
+        using var response = await _httpClient.SendAsync(request);
+
+        var headers = response.Headers;
+        Assert.Multiple(() =>
+        {
+            Assert.That(headers.Contains(headerName), Is.True);
+            Assert.That(headers.TryGetValues(headerName, out var values), Is.True);
+            Assert.That(values, Is.Not.Null);
+            Assert.That(values!.Count(), Is.EqualTo(1));
+            Assert.That(values!.First(), Is.EqualTo(headerValue));
+        });
+    }
 }

src/Teapot.Web/CustomHttpStatusCodeResult.cs

@@ -4,6 +4,7 @@
 using Microsoft.Net.Http.Headers;
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Text.Json;
 using System.Threading.Tasks;
 using Teapot.Web.Models;
@@ -19,6 +20,7 @@ public class CustomHttpStatusCodeResult(
 {
     private const int SLEEP_MIN = 0;
     private const int SLEEP_MAX = 5 * 60 * 1000; // 5 mins in milliseconds
+    private static readonly string[] onlySingleHeader = ["Location"];
 
     private static readonly MediaTypeHeaderValue jsonMimeType = new("application/json");
 
@@ -51,7 +53,14 @@ public async Task ExecuteAsync(HttpContext context)
 
         foreach ((string header, StringValues values) in customResponseHeaders)
         {
-            context.Response.Headers.Append(header, values);
+            if (onlySingleHeader.Contains(header))
+            {
+                context.Response.Headers[header] = values;
+            }
+            else
+            {
+                context.Response.Headers.Append(header, values);
+            }
         }
 
         if (metadata.ExcludeBody || suppressBody == true)