fix typo, pytest fixture

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (e5ceaf6) 81.73% compared to head (21f1d55) 81.74%.

:exclamation: Current head 21f1d55 differs from pull request most recent head c4aa696. Consider uploading reports for the commit c4aa696 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #484 +/- ## ======================================= Coverage 81.73% 81.74% ======================================= Files 80 79 -1 Lines 4719 4716 -3 Branches 807 807 ======================================= - Hits 3857 3855 -2 + Misses 659 658 -1 Partials 203 203 ``` | [Flag](https://app.codecov.io/gh/casact/chainladder-python/pull/484/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=casact) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/casact/chainladder-python/pull/484/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=casact) | `81.74% <ø> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=casact#carryforward-flags-in-the-pull-request-comment) to find out more.

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