TST/CLN: remove TestData from series-tests; replace with fixtures

[h-vetinari]

This is the sister-issue for Series of #22471 (for frames), where the review in #22236 requested:

ok, pls open a new issue that refs this, to remove use of TestData in favor of fixtures

For Series, this process is started by #22526 by creating a conftest.py that translates all the current attributes of TestData to fixtures, with the following "translation guide":

• ts -> datetime_series
• series -> string_series
• objSeries -> object_series
• empty -> empty_series

Need to incrementally replace their usages in pandas/tests/series/ (example below).

• Create conftest.py and translate TestData-attributes into fixtures and renaming them them as outlined above (TST: fixturize series/test_alter_axes.py #22526)
• test_alter_axes.py (TST: fixturize series/test_alter_axes.py #22526)
• test_analytics.py (TST: Fixturize series/test_analytics.py #22755)
• test_api.py (Remove TestData from series-tests test_api.py #29153)
• test_apply.py (TST: Fixturize series/test_apply.py #22769)
• test_asof.py (TST: Fixturize series/test_asof.py #22772)
• test_combine_concat.py (TST: Fixturize series/test_combine_concat.py #22964)
• test_constructors.py (TST: Fixturize series/test_constructors.py #22965)
• test_datetime_values.py (TST: Fixturize series/test_datetime_values.py #22966)
• test_dtypes.py (TST: Fixturize series/test_dtypes.py #22967)
• test_io.py (TST: Fixturize series/test_io.py #22972)
• test_missing.py (TST: Fixturize series/test_missing.py #22973)
• test_operators.py ([#22550] Remove TestData from series-tests test_operators.py #29084)
• test_quantile.py ([#22550] Remove TestData from series-tests test_quantile.py #29096)
• test_rank.py ([#22550] Remove TestData from series-tests test_rank.py #29101)
• test_replace.py (Remove TestData from series-tests test_replace.py #29147)
• test_repr.py (Remove TestData from series-tests test_repr.py #29148)
• test_sorting.py (Remove TestData from series-tests test_sorting.py #29149)
• test_timeseries.py (Remove TestData from series-tests test_timeseries.py #29150)
• test_validate.py (TST: Fixturize series/test_validate.py #22756)

Things for follow-ups:

• Remove other class-based test-methods
• Turn tests from class- to function-based

An example from #22526 - before:

def test_rename_inplace(self):
    renamer = lambda x: x.strftime('%Y%m%d')
    expected = renamer(self.ts.index[0])
    self.ts.rename(renamer, inplace=True)
    assert self.ts.index[0] == expected

After:

def test_rename_inplace(self, datetime_series):
    renamer = lambda x: x.strftime('%Y%m%d')
    expected = renamer(datetime_series.index[0])
    datetime_series.rename(renamer, inplace=True)
    assert datetime_series.index[0] == expected

Basically, it comes down to replacing all the occurrences of self.<name> with translation_guide[<name>] (and specifying the latter as a parameter to the function).

PS. Note that some fixtures added by #22526 have now been removed by #24885. Please check #24885 which code was removed, in case you should need it for the fixturisation. Alternatively, you can ping me, @jbrockmendel or @jreback.

[Anjali2019]

Hi! I am looking to start making open source contributions, tests seem like good place to start :)
If no one is working on this, can I take it up?

[h-vetinari]

@Anjali2019, sounds great, but you should wait until #22526 has been merged, otherwise the fixtures in conftest.py will not be available for you.

[Anjali2019]

@h-vetinari Sure! makes sense.

[h-vetinari]

@Anjali2019 good to go. :)
Probably best to start on a per-module basis.

[Anjali2019]

Awesome! Thanks. Will start on it :D

[SaturnFromTitan]

test_arithmetic.py also doesn't contain TestData, so after merging my pending PRs we can close this issue ✅

I guess the next step then would be to remove the pandas/tests/series/_common.py altogether

[SaturnFromTitan]

I created the follow-up issue to remove _common.py for series tests. This one here can be closed @simonjayhawkins ✌️

EDIT: I'll first need to remove TestData usage in pandas/tests/series/indexing