TST: Add test for less harder to reach places

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 97.50000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 90.84%. Comparing base (578219d) to head (43fc6fa).

Files with missing lines	Patch %	Lines
randomgen/entropy.pyx	86.66%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #379 +/- ## ========================================== + Coverage 90.31% 90.84% +0.52% ========================================== Files 53 53 Lines 8046 8124 +78 Branches 490 504 +14 ========================================== + Hits 7267 7380 +113 + Misses 753 718 -35 Partials 26 26 ``` | [Flag](https://app.codecov.io/gh/bashtage/randomgen/pull/379/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kevin+Sheppard) | Coverage Δ | | |---|---|---| | [](https://app.codecov.io/gh/bashtage/randomgen/pull/379/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kevin+Sheppard) | `90.82% <97.50%> (+0.52%)` | :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=Kevin+Sheppard#carryforward-flags-in-the-pull-request-comment) to find out more.

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