From 7d84878b84dd7f1ce346af783987eaf721185647 Mon Sep 17 00:00:00 2001
From: shteken <barshteken@gmail.com>
Date: Sun, 30 Apr 2023 11:03:31 +0200
Subject: [PATCH 1/2] add test_multiindex_with_na

---
 pandas/tests/test_multilevel.py | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/pandas/tests/test_multilevel.py b/pandas/tests/test_multilevel.py
index 199307dd138ca..7ae4411754d7b 100644
--- a/pandas/tests/test_multilevel.py
+++ b/pandas/tests/test_multilevel.py
@@ -290,6 +290,22 @@ def test_datetime_object_multiindex(self):
 
         tm.assert_frame_equal(result, expected)
 
+    def test_multiindex_with_na(self):
+        df = DataFrame(
+            [
+                ["A", np.nan, 1.23, 4.56],
+                ["A", "G", 1.23, 4.56],
+                ["A", "D", 9.87, 10.54],
+            ],
+            columns=["pivot_0", "pivot_1", "col_1", "col_2"],
+        )
+        df.set_index(["pivot_0", "pivot_1"], inplace=True)
+
+        df.at[("A", "F"), "col_2"] = 0.0
+
+        assert df.loc[("A", "F")]["col_2"] == 0.0
+        assert pd.isna(df.loc[("A", "F")]["col_1"])
+
 
 class TestSorted:
     """everything you wanted to test about sorting"""

From 7c2a5d1e888864258afef4e504d979c4bcc19005 Mon Sep 17 00:00:00 2001
From: shteken <barshteken@gmail.com>
Date: Tue, 2 May 2023 18:29:48 +0200
Subject: [PATCH 2/2] address comments in pr

---
 pandas/tests/test_multilevel.py | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/pandas/tests/test_multilevel.py b/pandas/tests/test_multilevel.py
index 7ae4411754d7b..8c5f9a894f2f7 100644
--- a/pandas/tests/test_multilevel.py
+++ b/pandas/tests/test_multilevel.py
@@ -298,13 +298,21 @@ def test_multiindex_with_na(self):
                 ["A", "D", 9.87, 10.54],
             ],
             columns=["pivot_0", "pivot_1", "col_1", "col_2"],
-        )
-        df.set_index(["pivot_0", "pivot_1"], inplace=True)
+        ).set_index(["pivot_0", "pivot_1"])
 
         df.at[("A", "F"), "col_2"] = 0.0
 
-        assert df.loc[("A", "F")]["col_2"] == 0.0
-        assert pd.isna(df.loc[("A", "F")]["col_1"])
+        expected = DataFrame(
+            [
+                ["A", np.nan, 1.23, 4.56],
+                ["A", "G", 1.23, 4.56],
+                ["A", "D", 9.87, 10.54],
+                ["A", "F", np.nan, 0.0],
+            ],
+            columns=["pivot_0", "pivot_1", "col_1", "col_2"],
+        ).set_index(["pivot_0", "pivot_1"])
+
+        tm.assert_frame_equal(df, expected)
 
 
 class TestSorted: