Fix: assertrepr_compare respects dict insertion order

changelog/14050.bugfix.rst

@@ -0,0 +1 @@
+Assertion comparison output now preserves dictionary insertion order instead of sorting keys.

src/_pytest/_io/saferepr.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from itertools import islice
 import pprint
 import reprlib
 
@@ -77,8 +78,32 @@ def repr_instance(self, x: object, level: int) -> str:
             s = _format_repr_exception(exc, x)
         if self.maxsize is not None:
             s = _ellipsize(s, self.maxsize)
+
         return s
 
+    def repr_dict(self, x: dict[object, object], level: int) -> str:
+        """Represent a dict while preserving its insertion order.
+
+        Differs from ``reprlib.Repr.repr_dict`` by iterating directly over ``x``
+        rather than using the stdlib's sorting helper.
+        """
+        fillvalue = "..."
+        n = len(x)
+        if n == 0:
+            return "{}"
+        if level <= 0:
+            return "{" + fillvalue + "}"
+        newlevel = level - 1
+        repr1 = self.repr1
+        pieces = []
+        for key in islice(x, self.maxdict):
+            keyrepr = repr1(key, newlevel)
+            valrepr = repr1(x[key], newlevel)
+            pieces.append(f"{keyrepr}: {valrepr}")
+        if n > self.maxdict:
+            pieces.append(fillvalue)
+        return "{" + ", ".join(pieces) + "}"
+
 
 def safeformat(obj: object) -> str:
     """Return a pretty printed string for the given object.

testing/io/test_saferepr.py

@@ -192,3 +192,31 @@ def __repr__(self):
     assert saferepr_unlimited(A()).startswith(
         "<[ValueError(42) raised in repr()] A object at 0x"
     )
+
+
+def test_saferepr_dict_preserves_insertion_order():
+    d = {"b": 1, "a": 2}
+    assert saferepr(d, maxsize=None) == "{'b': 1, 'a': 2}"
+
+
+def test_saferepr_dict_truncation_preserves_insertion_order():
+    from _pytest._io.saferepr import SafeRepr
+
+    d = {"b": 1, "a": 2}
+    s = SafeRepr(maxsize=None)
+    s.maxdict = 1
+    assert s.repr(d) == "{'b': 1, ...}"
+
+
+def test_saferepr_dict_fillvalue_when_level_is_zero():
+    from _pytest._io.saferepr import SafeRepr
+
+    s = SafeRepr(maxsize=None)
+    assert s.repr_dict({"a": 1}, level=0) == "{...}"
+
+
+def test_saferepr_dict_empty():
+    from _pytest._io.saferepr import SafeRepr
+
+    s = SafeRepr(maxsize=None)
+    assert s.repr_dict({}, level=1) == "{}"

testing/test_assertion.py

@@ -129,7 +129,7 @@ def test_dummy_failure(pytester):  # how meta!
             [
                 ">       r.assertoutcome(passed=1)",
                 "E       AssertionError: ([[][]], [[][]], [[]<TestReport *>[]])*",
-                "E       assert {'failed': 1,... 'skipped': 0} == {'failed': 0,... 'skipped': 0}",
+                "E       assert {'passed': 0,...*'failed': 1} == {'passed': 1,...*'failed': 0}",
                 "E         Omitting 1 identical items, use -vv to show",
                 "E         Differing items:",
                 "E         Use -v to get more diff",