address issue #52965: add tests

Author: litang99

pandas/tests/indexing/test_iloc.py

@@ -62,6 +62,22 @@ def test_iloc_getitem_int_and_list_int(self, key, frame_or_series, index, reques
         # array of ints (GH5006), make sure that a single indexer is returning
         # the correct type
 
+    @pytest.mark.parametrize(
+        "original_type, new_type",
+        [
+            (np.uint16, np.uint8),
+            (np.int32, np.int16),
+            (np.int64, np.uint64),
+            (np.int64, np.int16),
+        ],
+    )
+    def test_iloc_assign_preserve_dtype(self, original_type, new_type):
+        s = Series([10, 20, 30], index=list("abc"), dtype=original_type)
+        s.iloc[0:2] = np.array([100, 200], dtype=new_type)
+
+        expected = original_type
+        assert s.dtype == expected
+
 
 class TestiLocBaseIndependent:
     """Tests Independent Of Base Class"""

pandas/tests/indexing/test_loc.py

@@ -277,6 +277,22 @@ def test_loc_empty_slice_assignment_with_datetime(self, data):
         df.loc[mask] = df
         tm.assert_frame_equal(df, expected)
 
+    @pytest.mark.parametrize(
+        "original_type, new_type",
+        [
+            (np.uint16, np.uint8),
+            (np.int32, np.int16),
+            (np.int64, np.uint64),
+            (np.int64, np.int16),
+        ],
+    )
+    def test_loc_assign_preserve_dtype(self, original_type, new_type):
+        s = Series([10, 20, 30], index=list("abc"), dtype=original_type)
+        s.loc["a":"b"] = np.array([100, 200], dtype=new_type)
+
+        expected = original_type
+        assert s.dtype == expected
+
 
 class TestLocBaseIndependent:
     # Tests for loc that do not depend on subclassing Base