Expand unit test coverage

[aburrell]

Description

Fixes #5, #6, and #7 by either removing inaccessible lines, adding new tests, or removing support for the older versions of SciPy.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality
  to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Ran unit tests locally, with debug statements to check for increased coverage.

Test Configuration

• Operating system: OS X Tahoe
• Version number: Python 3.10
• Any details about your local setup that are relevant: scipy 1.14.1

Checklist:

• Make sure you are merging into the develop (not main) branch
• My commits are formatted appropriately (following the SciPy/NumPy style)
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• Add a note to Changelog.md, summarising the changes
• Add yourself to .zenodo.json