TST: implement test_setitem for Series

pandas/tests/indexes/datetimes/test_indexing.py

@@ -477,7 +477,7 @@ def test_get_loc_reasonable_key_error(self):
 
 
 class TestContains:
-    def test_index_dupes_contains(self):
+    def test_dti_contains_with_duplicates(self):
         d = datetime(2011, 12, 5, 20, 30)
         ix = DatetimeIndex([d, d])
         assert d in ix

pandas/tests/series/indexing/test_datetime.py

@@ -684,21 +684,6 @@ def test_indexing():
 """
 
 
-def test_set_none_nan():
-    series = Series(date_range("1/1/2000", periods=10))
-    series[3] = None
-    assert series[3] is NaT
-
-    series[3:5] = None
-    assert series[4] is NaT
-
-    series[5] = np.nan
-    assert series[5] is NaT
-
-    series[5:7] = np.nan
-    assert series[6] is NaT
-
-
 def test_setitem_tuple_with_datetimetz():
     # GH 20441
     arr = date_range("2017", periods=4, tz="US/Eastern")

pandas/tests/series/indexing/test_setitem.py

@@ -0,0 +1,19 @@
+import numpy as np
+
+from pandas import NaT, Series, date_range
+
+
+class TestSetitemDT64Values:
+    def test_setitem_none_nan(self):
+        series = Series(date_range("1/1/2000", periods=10))
+        series[3] = None
+        assert series[3] is NaT
+
+        series[3:5] = None
+        assert series[4] is NaT
+
+        series[5] = np.nan
+        assert series[5] is NaT
+
+        series[5:7] = np.nan
+        assert series[6] is NaT