RecyclableList.Insert fixed to allow inserting at the end.

Recyclable.Collections/RecyclableList.cs

@@ -385,7 +385,7 @@ namespace Recyclable.Collections
 				_capacity = RecyclableListHelpers<T>.ResizeAndCopy(this, checked((int)BitOperations.RoundUpToPowerOf2((uint)oldCount + 1)));
 			}
 
-			if (oldCount > 0)
+			if (index < oldCount)
 			{
 				new Span<T>(_memoryBlock, index, oldCount)
 					.CopyTo(new Span<T>(_memoryBlock, index + 1, oldCount));

Recyclable.CollectionsTests/RecyclableListTests.cs

@@ -471,6 +471,21 @@ namespace Recyclable.CollectionsTests
 			_ = list.Should().ContainInConsecutiveOrder(testData.Reverse());
 		}
 
+		[Theory]
+		[MemberData(nameof(RecyclableLongListTestData.SourceTargetDataVariants), MemberType = typeof(RecyclableLongListTestData))]
+		public void InsertAtTheEndShouldAppend(string testCase, IEnumerable<long> testData, long itemsCount, int targetBlockSize)
+		{
+			// Prepare
+			using var list = new RecyclableList<long>(testData);
+
+			// Act
+			list.Insert((int)itemsCount, -1);
+
+			// Assert
+			_ = list.Count.Should().Be((int)itemsCount + 1);
+			_ = list[^1].Should().Be(-1);
+		}
+
 		[Theory]
 		[MemberData(nameof(RecyclableLongListTestData.SourceDataVariants), MemberType = typeof(RecyclableLongListTestData))]
 		public void RemoveAtFromTheBeginningShouldSucceed(string testCase, IEnumerable<long> testData, long itemsCount)