Stabilize descending threaded-comments integration assertions

WordPressPCL.Tests.Selfhosted/CommentsThreaded_Tests.cs

@@ -244,12 +244,11 @@ public async Task CommentsThreaded_Sort_Extension_Desc()
         {
             // The following comment depth has to be the lower, equal or +1
             int ni = i + 1;
-            System.DateTime idate = threaded[i].Date;
-            System.DateTime nidate = threaded[ni].Date;
+            System.DateTime idate = firstLvl[i].Date;
+            System.DateTime nidate = firstLvl[ni].Date;
 
             // The following comment date has to be older
-            Assert.IsGreaterThan(threaded[ni].Id, threaded[i].Id);
-            Assert.IsLessThanOrEqualTo(nidate, idate);
+            Assert.IsTrue(nidate <= idate);
         }
     }
 

WordPressPCL.Tests.Selfhosted/Utility/ThreadedCommentsHelper_Tests.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using WordPressPCL.Models;
+using WordPressPCL.Utility;
+
+namespace WordPressPCL.Tests.Selfhosted.Utility;
+
+[TestClass]
+public class ThreadedCommentsHelper_Tests
+{
+    [TestMethod]
+    public void ToThreaded_Descending_KeepsTopLevelCommentsInDescendingDateOrder()
+    {
+        DateTime olderRootDate = new(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+        DateTime newerRootDate = new(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc);
+        DateTime newestChildDate = new(2026, 1, 3, 0, 0, 0, DateTimeKind.Utc);
+
+        List<Comment> comments =
+        [
+            new Comment { Id = 1, Date = newerRootDate },
+            new Comment { Id = 2, ParentId = 1, Date = newestChildDate },
+            new Comment { Id = 3, Date = olderRootDate }
+        ];
+
+        List<CommentThreaded>? threaded = comments.ToThreaded(true);
+
+        Assert.IsNotNull(threaded);
+        CollectionAssert.AreEqual(new[] { 1, 2, 3 }, threaded.Select(comment => comment.Id).ToList());
+
+        List<CommentThreaded> firstLevel = threaded.Where(comment => comment.Depth == 0).ToList();
+        CollectionAssert.AreEqual(new[] { 1, 3 }, firstLevel.Select(comment => comment.Id).ToList());
+        Assert.IsTrue(firstLevel[0].Date >= firstLevel[1].Date);
+    }
+}