diff --git a/pandas/tests/series/methods/test_tz_convert.py b/pandas/tests/series/methods/test_tz_convert.py
deleted file mode 100644
index d826dde646cfb..0000000000000
--- a/pandas/tests/series/methods/test_tz_convert.py
+++ /dev/null
@@ -1,17 +0,0 @@
-import numpy as np
-
-from pandas import (
-    DatetimeIndex,
-    Series,
-)
-import pandas._testing as tm
-
-
-class TestTZConvert:
-    def test_series_tz_convert_to_utc(self):
-        base = DatetimeIndex(["2011-01-01", "2011-01-02", "2011-01-03"], tz="UTC")
-        idx1 = base.tz_convert("Asia/Tokyo")[:2]
-        idx2 = base.tz_convert("US/Eastern")[1:]
-
-        res = Series([1, 2], index=idx1) + Series([1, 1], index=idx2)
-        tm.assert_series_equal(res, Series([np.nan, 3, np.nan], index=base))
diff --git a/pandas/tests/series/methods/test_tz_localize.py b/pandas/tests/series/methods/test_tz_localize.py
index a32c1fb8df502..b8a1ea55db4fe 100644
--- a/pandas/tests/series/methods/test_tz_localize.py
+++ b/pandas/tests/series/methods/test_tz_localize.py
@@ -68,22 +68,39 @@ def test_series_tz_localize_matching_index(self):
             ["foo", "invalid"],
         ],
     )
-    def test_series_tz_localize_nonexistent(self, tz, method, exp):
+    def test_tz_localize_nonexistent(self, tz, method, exp):
         # GH 8917
         n = 60
         dti = date_range(start="2015-03-29 02:00:00", periods=n, freq="min")
-        s = Series(1, dti)
+        ser = Series(1, index=dti)
+        df = ser.to_frame()
+
         if method == "raise":
+
+            with tm.external_error_raised(pytz.NonExistentTimeError):
+                dti.tz_localize(tz, nonexistent=method)
+            with tm.external_error_raised(pytz.NonExistentTimeError):
+                ser.tz_localize(tz, nonexistent=method)
             with tm.external_error_raised(pytz.NonExistentTimeError):
-                s.tz_localize(tz, nonexistent=method)
+                df.tz_localize(tz, nonexistent=method)
+
         elif exp == "invalid":
             with pytest.raises(ValueError, match="argument must be one of"):
                 dti.tz_localize(tz, nonexistent=method)
+            with pytest.raises(ValueError, match="argument must be one of"):
+                ser.tz_localize(tz, nonexistent=method)
+            with pytest.raises(ValueError, match="argument must be one of"):
+                df.tz_localize(tz, nonexistent=method)
+
         else:
-            result = s.tz_localize(tz, nonexistent=method)
+            result = ser.tz_localize(tz, nonexistent=method)
             expected = Series(1, index=DatetimeIndex([exp] * n, tz=tz))
             tm.assert_series_equal(result, expected)
 
+            result = df.tz_localize(tz, nonexistent=method)
+            expected = expected.to_frame()
+            tm.assert_frame_equal(result, expected)
+
     @pytest.mark.parametrize("tzstr", ["US/Eastern", "dateutil/US/Eastern"])
     def test_series_tz_localize_empty(self, tzstr):
         # GH#2248
diff --git a/pandas/tests/series/test_arithmetic.py b/pandas/tests/series/test_arithmetic.py
index 103130484f0e1..e4f9366be8dd7 100644
--- a/pandas/tests/series/test_arithmetic.py
+++ b/pandas/tests/series/test_arithmetic.py
@@ -714,6 +714,16 @@ def test_series_add_tz_mismatch_converts_to_utc(self):
         assert result.index.tz == pytz.UTC
         tm.assert_series_equal(result, expected)
 
+    # TODO: redundant with test_series_add_tz_mismatch_converts_to_utc?
+    def test_series_arithmetic_mismatched_tzs_convert_to_utc(self):
+        base = pd.DatetimeIndex(["2011-01-01", "2011-01-02", "2011-01-03"], tz="UTC")
+        idx1 = base.tz_convert("Asia/Tokyo")[:2]
+        idx2 = base.tz_convert("US/Eastern")[1:]
+
+        res = Series([1, 2], index=idx1) + Series([1, 1], index=idx2)
+        expected = Series([np.nan, 3, np.nan], index=base)
+        tm.assert_series_equal(res, expected)
+
     def test_series_add_aware_naive_raises(self):
         rng = date_range("1/1/2011", periods=10, freq="H")
         ser = Series(np.random.randn(len(rng)), index=rng)