From 3c6f3cdf853c9b65c5e60997209c5aa1ec1838be Mon Sep 17 00:00:00 2001
From: Shahar Naveh <50263213+ShaharNaveh@users.noreply.github.com>
Date: Fri, 30 Apr 2021 02:34:45 +0300
Subject: [PATCH] TST: Regression test for #33765 (#41169)

---
 pandas/tests/frame/test_arithmetic.py | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/pandas/tests/frame/test_arithmetic.py b/pandas/tests/frame/test_arithmetic.py
index 3c8941c6361e0..b9f6e72acf71b 100644
--- a/pandas/tests/frame/test_arithmetic.py
+++ b/pandas/tests/frame/test_arithmetic.py
@@ -12,6 +12,7 @@
 import pandas as pd
 from pandas import (
     DataFrame,
+    Index,
     MultiIndex,
     Series,
 )
@@ -1816,3 +1817,22 @@ def test_inplace_arithmetic_series_update():
 
     expected = DataFrame({"A": [2, 3, 4]})
     tm.assert_frame_equal(df, expected)
+
+
+def test_arithemetic_multiindex_align():
+    """
+    Regression test for: https://github.com/pandas-dev/pandas/issues/33765
+    """
+    df1 = DataFrame(
+        [[1]],
+        index=["a"],
+        columns=MultiIndex.from_product([[0], [1]], names=["a", "b"]),
+    )
+    df2 = DataFrame([[1]], index=["a"], columns=Index([0], name="a"))
+    expected = DataFrame(
+        [[0]],
+        index=["a"],
+        columns=MultiIndex.from_product([[0], [1]], names=["a", "b"]),
+    )
+    result = df1 - df2
+    tm.assert_frame_equal(result, expected)