From 001ebf1e046c202cb337f010026fb5620cbeba6c Mon Sep 17 00:00:00 2001
From: Vinod Kumar <codingkiddo@gmail.com>
Date: Thu, 14 May 2026 21:09:18 +0530
Subject: [PATCH 1/3] Support generic mappings in assertion comparison

---
 src/_pytest/assertion/util.py |  4 ++--
 testing/test_assertion.py     | 30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/src/_pytest/assertion/util.py b/src/_pytest/assertion/util.py
index 07918a66284..d4ff86da52d 100644
--- a/src/_pytest/assertion/util.py
+++ b/src/_pytest/assertion/util.py
@@ -127,8 +127,8 @@ def istext(x: object) -> TypeGuard[str]:
     return isinstance(x, str)
 
 
-def isdict(x: object) -> TypeGuard[dict[object, object]]:
-    return isinstance(x, dict)
+def isdict(x: object) -> TypeGuard[Mapping[object, object]]:
+    return isinstance(x, Mapping)
 
 
 def isset(x: object) -> TypeGuard[set[object] | frozenset[object]]:
diff --git a/testing/test_assertion.py b/testing/test_assertion.py
index 9a7305a2905..2a5a196dbcb 100644
--- a/testing/test_assertion.py
+++ b/testing/test_assertion.py
@@ -1,7 +1,9 @@
 # mypy: allow-untyped-defs
 from __future__ import annotations
 
+from collections.abc import Mapping
 from collections.abc import MutableSequence
+
 import sys
 import textwrap
 from typing import Any
@@ -719,6 +721,34 @@ def test_dict_wrap(self) -> None:
             "  }",
         ]
 
+    def test_Mapping(self) -> None:
+        # Test comparing with a Mapping implementation that is not a dict subclass.
+        class TestMapping(Mapping[str, int]):
+            def __init__(self, values: dict[str, int]) -> None:
+                self.values = values
+
+            def __getitem__(self, key: str) -> int:
+                return self.values[key]
+
+            def __iter__(self):
+                return iter(self.values)
+
+            def __len__(self) -> int:
+                return len(self.values)
+
+        lines = callequal(
+            TestMapping({"a": 0, "b": 1}),
+            TestMapping({"a": 1, "b": 1}),
+        )
+
+        assert lines is not None
+        assert any(
+            line.startswith("Omitting 1 identical item")
+            for line in lines
+        )
+        assert "Differing items:" in lines
+        assert "{'a': 0} != {'a': 1}" in lines
+
     def test_dict(self) -> None:
         expl = callequal({"a": 0}, {"a": 1})
         assert expl is not None

From eac6d11b6f4bf080ab606a1d4c8f8ae5d85a1401 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 14 May 2026 15:40:59 +0000
Subject: [PATCH 2/3] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 testing/test_assertion.py | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/testing/test_assertion.py b/testing/test_assertion.py
index 2a5a196dbcb..4a487a0b7fe 100644
--- a/testing/test_assertion.py
+++ b/testing/test_assertion.py
@@ -3,7 +3,6 @@
 
 from collections.abc import Mapping
 from collections.abc import MutableSequence
-
 import sys
 import textwrap
 from typing import Any
@@ -742,10 +741,7 @@ def __len__(self) -> int:
         )
 
         assert lines is not None
-        assert any(
-            line.startswith("Omitting 1 identical item")
-            for line in lines
-        )
+        assert any(line.startswith("Omitting 1 identical item") for line in lines)
         assert "Differing items:" in lines
         assert "{'a': 0} != {'a': 1}" in lines
 

From 6691904d09cd889aff5e67182a28605bbe558893 Mon Sep 17 00:00:00 2001
From: Vinod Kumar <codingkiddo@gmail.com>
Date: Thu, 14 May 2026 21:17:04 +0530
Subject: [PATCH 3/3] Add changelog entry for generic mapping assertion diffs

---
 changelog/14461.bugfix.rst | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 changelog/14461.bugfix.rst

diff --git a/changelog/14461.bugfix.rst b/changelog/14461.bugfix.rst
new file mode 100644
index 00000000000..01c5f2ec964
--- /dev/null
+++ b/changelog/14461.bugfix.rst
@@ -0,0 +1,2 @@
+Assertion diffs now use mapping-specific output for objects implementing
+:class:`collections.abc.Mapping`, not only concrete :class:`dict` instances.