TST: split up test_concat.py pandas-dev#37243

 * reverted changes to test_series.py

pandas/tests/reshape/concat/test_series.py

@@ -15,6 +15,12 @@
 import pandas._testing as tm
 
 
+@pytest.fixture(params=[True, False])
+def sort(request):
+    """Boolean sort keyword for concat and DataFrame.append."""
+    return request.param
+
+
 class TestSeriesConcat:
     def test_concat_series(self):
 
@@ -46,7 +52,7 @@ def test_concat_empty_and_non_empty_series_regression(self):
         result = pd.concat([s1, s2])
         tm.assert_series_equal(result, expected)
 
-    def test_concat_series_axis1(self, sort=True):
+    def test_concat_series_axis1(self, sort=sort):
         ts = tm.makeTimeSeries()
 
         pieces = [ts[:-2], ts[2:], ts[2:-2]]
@@ -76,7 +82,6 @@ def test_concat_series_axis1(self, sort=True):
         s2 = Series(randn(4), index=["d", "a", "b", "c"], name="B")
         result = concat([s, s2], axis=1, sort=sort)
         expected = DataFrame({"A": s, "B": s2})
-
         tm.assert_frame_equal(result, expected)
 
     def test_concat_series_axis1_names_applied(self):