CLN: Split test_fields.py (pandas-dev#44816)

Author: mroeschke

pandas/tests/tslibs/test_fields.py

@@ -1,28 +1,39 @@
 import numpy as np
+import pytest
 
 from pandas._libs.tslibs import fields
 
 import pandas._testing as tm
 
 
-def test_fields_readonly():
-    # https://github.com/vaexio/vaex/issues/357
-    #  fields functions shouldn't raise when we pass read-only data
+@pytest.fixture
+def dtindex():
     dtindex = np.arange(5, dtype=np.int64) * 10 ** 9 * 3600 * 24 * 32
     dtindex.flags.writeable = False
+    return dtindex
 
+
+def test_get_date_name_field_readonly(dtindex):
+    # https://github.com/vaexio/vaex/issues/357
+    #  fields functions shouldn't raise when we pass read-only data
     result = fields.get_date_name_field(dtindex, "month_name")
     expected = np.array(["January", "February", "March", "April", "May"], dtype=object)
     tm.assert_numpy_array_equal(result, expected)
 
+
+def test_get_date_field_readonly(dtindex):
     result = fields.get_date_field(dtindex, "Y")
     expected = np.array([1970, 1970, 1970, 1970, 1970], dtype=np.int32)
     tm.assert_numpy_array_equal(result, expected)
 
+
+def test_get_start_end_field_readonly(dtindex):
     result = fields.get_start_end_field(dtindex, "is_month_start", None)
     expected = np.array([True, False, False, False, False], dtype=np.bool_)
     tm.assert_numpy_array_equal(result, expected)
 
+
+def test_get_timedelta_field_readonly(dtindex):
     # treat dtindex as timedeltas for this next one
     result = fields.get_timedelta_field(dtindex, "days")
     expected = np.arange(5, dtype=np.int32) * 32