From ca40380e99c2cdaab1d0c041f9f28cff37ef8ff9 Mon Sep 17 00:00:00 2001
From: Jay <43951088+jayendra-patil33@users.noreply.github.com>
Date: Tue, 24 Jan 2023 15:37:42 +0530
Subject: [PATCH] Add check for zero denominator in approx (#10624)

Closes #10533
---
 changelog/10533.bugfix.rst |  1 +
 src/_pytest/python_api.py  | 14 ++++++++++----
 testing/python/approx.py   | 13 +++++++++++++
 3 files changed, 24 insertions(+), 4 deletions(-)
 create mode 100644 changelog/10533.bugfix.rst

diff --git a/changelog/10533.bugfix.rst b/changelog/10533.bugfix.rst
new file mode 100644
index 000000000..c49e4c3aa
--- /dev/null
+++ b/changelog/10533.bugfix.rst
@@ -0,0 +1 @@
+Fix :func:`pytest.approx` handling of dictionaries containing one or more values of `0.0` in class ApproxMapping.
diff --git a/src/_pytest/python_api.py b/src/_pytest/python_api.py
index 4bc934861..e1cbce210 100644
--- a/src/_pytest/python_api.py
+++ b/src/_pytest/python_api.py
@@ -269,10 +269,16 @@ class ApproxMapping(ApproxBase):
                 max_abs_diff = max(
                     max_abs_diff, abs(approx_value.expected - other_value)
                 )
-                max_rel_diff = max(
-                    max_rel_diff,
-                    abs((approx_value.expected - other_value) / approx_value.expected),
-                )
+                if approx_value.expected == 0.0:
+                    max_rel_diff = math.inf
+                else:
+                    max_rel_diff = max(
+                        max_rel_diff,
+                        abs(
+                            (approx_value.expected - other_value)
+                            / approx_value.expected
+                        ),
+                    )
                 different_ids.append(approx_key)
 
         message_data = [
diff --git a/testing/python/approx.py b/testing/python/approx.py
index 6acb466ff..631e52b56 100644
--- a/testing/python/approx.py
+++ b/testing/python/approx.py
@@ -630,6 +630,19 @@ class TestApprox:
     def test_dict_vs_other(self):
         assert 1 != approx({"a": 0})
 
+    def test_dict_for_div_by_zero(self, assert_approx_raises_regex):
+        assert_approx_raises_regex(
+            {"foo": 42.0},
+            {"foo": 0.0},
+            [
+                r"  comparison failed. Mismatched elements: 1 / 1:",
+                rf"  Max absolute difference: {SOME_FLOAT}",
+                r"  Max relative difference: inf",
+                r"  Index \| Obtained\s+\| Expected   ",
+                rf"  foo   | {SOME_FLOAT} \| {SOME_FLOAT} ± {SOME_FLOAT}",
+            ],
+        )
+
     def test_numpy_array(self):
         np = pytest.importorskip("numpy")