TST: Add test for boxable categories GH#21658

Signed-off-by: Liang Yan <[email protected]>

Author: liang3zy22

pandas/tests/dtypes/test_common.py

@@ -782,3 +782,39 @@ def test_pandas_dtype_numpy_warning():
         match="Converting `np.integer` or `np.signedinteger` to a dtype is deprecated",
     ):
         pandas_dtype(np.integer)
+
+
+def test_boxable_categorical_values():
+    cat = pd.Categorical(pd.date_range("2012-01-01", periods=3, freq="H"))
+    result = pd.MultiIndex.from_product([["a", "b", "c"], cat]).values
+    expected = pd.Series(
+        [
+            ("a", pd.Timestamp("2012-01-01 00:00:00")),
+            ("a", pd.Timestamp("2012-01-01 01:00:00")),
+            ("a", pd.Timestamp("2012-01-01 02:00:00")),
+            ("b", pd.Timestamp("2012-01-01 00:00:00")),
+            ("b", pd.Timestamp("2012-01-01 01:00:00")),
+            ("b", pd.Timestamp("2012-01-01 02:00:00")),
+            ("c", pd.Timestamp("2012-01-01 00:00:00")),
+            ("c", pd.Timestamp("2012-01-01 01:00:00")),
+            ("c", pd.Timestamp("2012-01-01 02:00:00")),
+        ]
+    ).values
+    tm.assert_numpy_array_equal(result, expected)
+    result = pd.DataFrame({"a": ["a", "b", "c"], "b": cat, "c": np.array(cat)}).values
+    expected = pd.DataFrame(
+        {
+            "a": ["a", "b", "c"],
+            "b": [
+                pd.Timestamp("2012-01-01 00:00:00"),
+                pd.Timestamp("2012-01-01 01:00:00"),
+                pd.Timestamp("2012-01-01 02:00:00"),
+            ],
+            "c": [
+                pd.Timestamp("2012-01-01 00:00:00"),
+                pd.Timestamp("2012-01-01 01:00:00"),
+                pd.Timestamp("2012-01-01 02:00:00"),
+            ],
+        }
+    ).values
+    tm.assert_numpy_array_equal(result, expected)