Fix representation of tuples in approx

Closes #9917

AUTHORS

@@ -361,5 +361,6 @@ Yoav Caspi
 Yuval Shimon
 Zac Hatfield-Dodds
 Zachary Kneupper
+Zachary OBrien
 Zoltán Máté
 Zsolt Cserna

changelog/9917.bugfix.rst

@@ -0,0 +1 @@
+Fixed string representation for :func:`pytest.approx` when used to compare tuples.

src/_pytest/python_api.py

@@ -133,9 +133,11 @@ def _check_type(self) -> None:
         # raise if there are any non-numeric elements in the sequence.
 
 
-def _recursive_list_map(f, x):
-    if isinstance(x, list):
-        return [_recursive_list_map(f, xi) for xi in x]
+def _recursive_sequence_map(f, x):
+    """Recursively map a function over a sequence of arbitary depth"""
+    if isinstance(x, (list, tuple)):
+        seq_type = type(x)
+        return seq_type(_recursive_sequence_map(f, xi) for xi in x)
     else:
         return f(x)
 
@@ -144,7 +146,9 @@ class ApproxNumpy(ApproxBase):
     """Perform approximate comparisons where the expected value is numpy array."""
 
     def __repr__(self) -> str:
-        list_scalars = _recursive_list_map(self._approx_scalar, self.expected.tolist())
+        list_scalars = _recursive_sequence_map(
+            self._approx_scalar, self.expected.tolist()
+        )
         return f"approx({list_scalars!r})"
 
     def _repr_compare(self, other_side: "ndarray") -> List[str]:
@@ -164,7 +168,7 @@ def get_value_from_nested_list(
             return value
 
         np_array_shape = self.expected.shape
-        approx_side_as_list = _recursive_list_map(
+        approx_side_as_seq = _recursive_sequence_map(
             self._approx_scalar, self.expected.tolist()
         )
 
@@ -179,7 +183,7 @@ def get_value_from_nested_list(
         max_rel_diff = -math.inf
         different_ids = []
         for index in itertools.product(*(range(i) for i in np_array_shape)):
-            approx_value = get_value_from_nested_list(approx_side_as_list, index)
+            approx_value = get_value_from_nested_list(approx_side_as_seq, index)
             other_value = get_value_from_nested_list(other_side, index)
             if approx_value != other_value:
                 abs_diff = abs(approx_value.expected - other_value)
@@ -194,7 +198,7 @@ def get_value_from_nested_list(
             (
                 str(index),
                 str(get_value_from_nested_list(other_side, index)),
-                str(get_value_from_nested_list(approx_side_as_list, index)),
+                str(get_value_from_nested_list(approx_side_as_seq, index)),
             )
             for index in different_ids
         ]
@@ -326,7 +330,7 @@ def _repr_compare(self, other_side: Sequence[float]) -> List[str]:
                 f"Lengths: {len(self.expected)} and {len(other_side)}",
             ]
 
-        approx_side_as_map = _recursive_list_map(self._approx_scalar, self.expected)
+        approx_side_as_map = _recursive_sequence_map(self._approx_scalar, self.expected)
 
         number_of_elements = len(approx_side_as_map)
         max_abs_diff = -math.inf

testing/python/approx.py

@@ -2,12 +2,14 @@
 from contextlib import contextmanager
 from decimal import Decimal
 from fractions import Fraction
+from math import sqrt
 from operator import eq
 from operator import ne
 from typing import Optional
 
 import pytest
 from _pytest.pytester import Pytester
+from _pytest.python_api import _recursive_sequence_map
 from pytest import approx
 
 inf, nan = float("inf"), float("nan")
@@ -133,6 +135,18 @@ def test_error_messages_native_dtypes(self, assert_approx_raises_regex):
             ],
         )
 
+        assert_approx_raises_regex(
+            (1, 2.2, 4),
+            (1, 3.2, 4),
+            [
+                r"  comparison failed. Mismatched elements: 1 / 3:",
+                rf"  Max absolute difference: {SOME_FLOAT}",
+                rf"  Max relative difference: {SOME_FLOAT}",
+                r"  Index \| Obtained\s+\| Expected   ",
+                rf"  1     \| {SOME_FLOAT} \| {SOME_FLOAT} ± {SOME_FLOAT}",
+            ],
+        )
+
         # Specific test for comparison with 0.0 (relative diff will be 'inf')
         assert_approx_raises_regex(
             [0.0],
@@ -878,3 +892,31 @@ def test_allow_ordered_sequences_only(self) -> None:
         """pytest.approx() should raise an error on unordered sequences (#9692)."""
         with pytest.raises(TypeError, match="only supports ordered sequences"):
             assert {1, 2, 3} == approx({1, 2, 3})
+
+
+class TestRecursiveSequenceMap:
+    def test_map_over_scalar(self):
+        assert _recursive_sequence_map(sqrt, 16) == 4
+
+    def test_map_over_empty_list(self):
+        assert _recursive_sequence_map(sqrt, []) == []
+
+    def test_map_over_list(self):
+        assert _recursive_sequence_map(sqrt, [4, 16, 25, 676]) == [2, 4, 5, 26]
+
+    def test_map_over_tuple(self):
+        assert _recursive_sequence_map(sqrt, (4, 16, 25, 676)) == (2, 4, 5, 26)
+
+    def test_map_over_nested_lists(self):
+        assert _recursive_sequence_map(sqrt, [4, [25, 64], [[49]]]) == [
+            2,
+            [5, 8],
+            [[7]],
+        ]
+
+    def test_map_over_mixed_sequence(self):
+        assert _recursive_sequence_map(sqrt, [4, (25, 64), [(49)]]) == [
+            2,
+            (5, 8),
+            [(7)],
+        ]