From baad8c07045fc3365aef52ed63ca3d4591798fcb Mon Sep 17 00:00:00 2001
From: croc100 <croc100100@gmail.com>
Date: Mon, 8 Jun 2026 20:15:27 +0900
Subject: [PATCH 1/3] Fix isset() to include dict.items() and dict.keys() in
 set comparisons

isset() was limited to set/frozenset, so assert expressions like
dict.items() >= other.items() fell through without any diff output.

dict.items() and dict.keys() both implement collections.abc.Set, so
widening the check to isinstance(x, AbstractSet) is enough.

Fixes #12860
---
 src/_pytest/assertion/_guards.py |  5 +++--
 testing/test_assertion.py        | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/src/_pytest/assertion/_guards.py b/src/_pytest/assertion/_guards.py
index bb9fedd6e65..d8d786ece6f 100644
--- a/src/_pytest/assertion/_guards.py
+++ b/src/_pytest/assertion/_guards.py
@@ -2,6 +2,7 @@
 
 import collections.abc
 from collections.abc import Mapping
+from collections.abc import Set as AbstractSet
 import dataclasses
 from typing import TypeGuard
 
@@ -18,8 +19,8 @@ def ismapping(x: object) -> TypeGuard[Mapping[object, object]]:
     return isinstance(x, Mapping)
 
 
-def isset(x: object) -> TypeGuard[set[object] | frozenset[object]]:
-    return isinstance(x, set | frozenset)
+def isset(x: object) -> TypeGuard[AbstractSet[object]]:
+    return isinstance(x, AbstractSet)
 
 
 def isnamedtuple(obj: object) -> bool:
diff --git a/testing/test_assertion.py b/testing/test_assertion.py
index c25487bdf33..e68a4c6132a 100644
--- a/testing/test_assertion.py
+++ b/testing/test_assertion.py
@@ -1870,6 +1870,38 @@ def test_hello():
             ]
         )
 
+    @pytest.mark.parametrize("op", [">=", "<="])
+    def test_dict_items_view_subset(self, op, pytester: Pytester) -> None:
+        """dict.items() supports set-like comparisons; assert diff should show the missing items."""
+        if op == ">=":
+            pytester.makepyfile(
+                """
+                def test_hello():
+                    x = {"a": 1, "b": 2}
+                    y = {"a": 1, "b": 2, "c": 3}
+                    assert x.items() >= y.items()
+            """
+            )
+        else:
+            pytester.makepyfile(
+                """
+                def test_hello():
+                    x = {"a": 1, "b": 2, "c": 3}
+                    y = {"a": 1, "b": 2}
+                    assert x.items() <= y.items()
+            """
+            )
+        result = pytester.runpytest()
+        side = "right" if op == ">=" else "left"
+        result.stdout.fnmatch_lines(
+            [
+                "*def test_hello():*",
+                f"*assert x.items() {op} y.items()*",
+                f"*E*Extra items in the {side} set:*",
+                "*E*('c', 3)*",
+            ]
+        )
+
 
 def test_assertrepr_loaded_per_dir(pytester: Pytester) -> None:
     pytester.makepyfile(test_base=["def test_base(): assert 1 == 2"])

From 97a1d3d809bf4260320800ea566e9ea70da58a34 Mon Sep 17 00:00:00 2001
From: croc100 <croc100100@gmail.com>
Date: Mon, 8 Jun 2026 20:17:33 +0900
Subject: [PATCH 2/3] Add changelog fragment for #12860

---
 changelog/12860.improvement.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog/12860.improvement.rst

diff --git a/changelog/12860.improvement.rst b/changelog/12860.improvement.rst
new file mode 100644
index 00000000000..2ea7492bc10
--- /dev/null
+++ b/changelog/12860.improvement.rst
@@ -0,0 +1 @@
+Assertion diffs for ``dict.items()`` and ``dict.keys()`` comparisons (``>=``, ``<=``, ``>``, ``<``, ``==``) now show which items are missing, the same way set comparisons do.

From 451cfdcfe2ea07ebf3f9454169ce8c8b0b4198c7 Mon Sep 17 00:00:00 2001
From: croc100 <croc100100@gmail.com>
Date: Mon, 8 Jun 2026 20:19:03 +0900
Subject: [PATCH 3/3] Add croc100 to AUTHORS

---
 AUTHORS | 1 +
 1 file changed, 1 insertion(+)

diff --git a/AUTHORS b/AUTHORS
index 27c0b3ac408..9ab7b823945 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -80,6 +80,7 @@ Brian Okken
 Brianna Laugher
 Bruno Oliveira
 Cal Jacobson
+croc100
 Cal Leeming
 Carl Friedrich Bolz
 Carlos Jenkins