Added two tests for issue #29697 (#33508)

Author: devjeetr

pandas/tests/reshape/merge/test_merge.py

@@ -2024,6 +2024,36 @@ def test_merge_suffix(col1, col2, kwargs, expected_cols):
     tm.assert_frame_equal(result, expected)
 
 
+@pytest.mark.parametrize(
+    "how,expected",
+    [
+        (
+            "right",
+            DataFrame(
+                {"A": [100, 200, 300], "B1": [60, 70, np.nan], "B2": [600, 700, 800]}
+            ),
+        ),
+        (
+            "outer",
+            DataFrame(
+                {
+                    "A": [100, 200, 1, 300],
+                    "B1": [60, 70, 80, np.nan],
+                    "B2": [600, 700, np.nan, 800],
+                }
+            ),
+        ),
+    ],
+)
+def test_merge_duplicate_suffix(how, expected):
+    left_df = DataFrame({"A": [100, 200, 1], "B": [60, 70, 80]})
+    right_df = DataFrame({"A": [100, 200, 300], "B": [600, 700, 800]})
+    result = merge(left_df, right_df, on="A", how=how, suffixes=("_x", "_x"))
+    expected.columns = ["A", "B_x", "B_x"]
+
+    tm.assert_frame_equal(result, expected)
+
+
 @pytest.mark.parametrize(
     "col1, col2, suffixes",
     [