TST: Update test_merge_multiindex_columns

Author: nrebena

pandas/tests/reshape/merge/test_merge.py

@@ -2102,25 +2102,25 @@ def test_merge_multiindex_columns():
     # The original cause of this issue come from a bug lexsort_depth and is tested in
     # test_lexsort_depth
 
-    index_tuples = []
     letters = ["a", "b", "c", "d"]
     numbers = ["1", "2", "3"]
-
-    for l in letters:
-        for n in numbers:
-            index_tuples.append([l, n])
-
-    index = pd.MultiIndex.from_tuples(index_tuples, names=["outer", "inner"])
+    index = pd.MultiIndex.from_product((letters, numbers), names=["outer", "inner"])
 
     frame_x = pd.DataFrame(columns=index)
     frame_x["id"] = ""
-
     frame_y = pd.DataFrame(columns=index)
     frame_y["id"] = ""
 
     l_suf = "_x"
     r_suf = "_y"
-    expected_labels = sum(([l + l_suf, l + r_suf] for l in letters), [])
-    merged_frame = frame_x.merge(frame_y, on="id", suffixes=((l_suf, r_suf))).columns
-    for label in expected_labels:
-        assert label in merged_frame
+    result = frame_x.merge(frame_y, on="id", suffixes=((l_suf, r_suf)))
+
+    # Constructing the expected results
+    expected_labels = [l + l_suf for l in letters] + [l + r_suf for l in letters]
+    expected_index = pd.MultiIndex.from_product(
+        [expected_labels, numbers], names=["outer", "inner"]
+    )
+    expected = pd.DataFrame(columns=expected_index)
+    expected["id"] = ""
+
+    tm.assert_frame_equal(result, expected)