From 58e9ab54cf111dbf393763625702ffd5a2f0f098 Mon Sep 17 00:00:00 2001
From: Giancarlo Cicellyn Comneno <126195429+gcomneno@users.noreply.github.com>
Date: Fri, 2 Oct 2026 08:34:11 +0200
Subject: [PATCH 1/3] test: cover insertion sort stability with equal-priority
 items

---
 sorts/insertion_sort.py | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/sorts/insertion_sort.py b/sorts/insertion_sort.py
index e339e5062a27..95709c5cd65c 100644
--- a/sorts/insertion_sort.py
+++ b/sorts/insertion_sort.py
@@ -56,6 +56,17 @@ def insertion_sort[T: Comparable](collection: MutableSequence[T]) -> MutableSequ
     True
     >>> values
     [1, 2, 4, 7]
+
+    Equal-priority items retain their original relative order:
+    >>> from dataclasses import dataclass, field
+    >>> @dataclass(order=True)
+    ... class Item:
+    ...     priority: int
+    ...     label: str = field(compare=False)
+    >>> items = [Item(2, "A"), Item(1, "X"), Item(2, "B"), Item(1, "Y")]
+    >>> [(item.priority, item.label) for item in insertion_sort(items)]
+    [(1, 'X'), (1, 'Y'), (2, 'A'), (2, 'B')]
+
     >>> import random
     >>> collection = random.sample(range(-50, 50), 100)
     >>> insertion_sort(collection) == sorted(collection)

From e9bd4668d078947dce578a75cc45181244e7c540 Mon Sep 17 00:00:00 2001
From: Giancarlo Cicellyn Comneno <126195429+gcomneno@users.noreply.github.com>
Date: Sat, 3 Oct 2026 07:59:47 +0200
Subject: [PATCH 2/3] test: simplify insertion sort stability doctest output

---
 sorts/insertion_sort.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sorts/insertion_sort.py b/sorts/insertion_sort.py
index 95709c5cd65c..03bfe4ec1a0d 100644
--- a/sorts/insertion_sort.py
+++ b/sorts/insertion_sort.py
@@ -64,8 +64,9 @@ def insertion_sort[T: Comparable](collection: MutableSequence[T]) -> MutableSequ
     ...     priority: int
     ...     label: str = field(compare=False)
     >>> items = [Item(2, "A"), Item(1, "X"), Item(2, "B"), Item(1, "Y")]
-    >>> [(item.priority, item.label) for item in insertion_sort(items)]
-    [(1, 'X'), (1, 'Y'), (2, 'A'), (2, 'B')]
+    >>> insertion_sort(items)  # doctest: +NORMALIZE_WHITESPACE
+    [Item(priority=1, label='X'), Item(priority=1, label='Y'),
+     Item(priority=2, label='A'), Item(priority=2, label='B')]
 
     >>> import random
     >>> collection = random.sample(range(-50, 50), 100)

From 3e020fd5089813a8fcc2c1653c35e80906425659 Mon Sep 17 00:00:00 2001
From: Giancarlo Cicellyn Comneno <126195429+gcomneno@users.noreply.github.com>
Date: Sat, 3 Oct 2026 08:34:43 +0200
Subject: [PATCH 3/3] test: verify insertion sort ignores labels when ordering

---
 sorts/insertion_sort.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sorts/insertion_sort.py b/sorts/insertion_sort.py
index 03bfe4ec1a0d..ae5edca3f60f 100644
--- a/sorts/insertion_sort.py
+++ b/sorts/insertion_sort.py
@@ -67,6 +67,10 @@ def insertion_sort[T: Comparable](collection: MutableSequence[T]) -> MutableSequ
     >>> insertion_sort(items)  # doctest: +NORMALIZE_WHITESPACE
     [Item(priority=1, label='X'), Item(priority=1, label='Y'),
      Item(priority=2, label='A'), Item(priority=2, label='B')]
+    >>> other = [Item(2, "B"), Item(1, "Y"), Item(2, "A"), Item(1, "X")]
+    >>> insertion_sort(other)  # doctest: +NORMALIZE_WHITESPACE
+    [Item(priority=1, label='Y'), Item(priority=1, label='X'),
+     Item(priority=2, label='B'), Item(priority=2, label='A')]
 
     >>> import random
     >>> collection = random.sample(range(-50, 50), 100)