Write pytest tests for all functions

[nrweir]

Write pytest tests for all functions in the module

This is marked as hard not due to the intrinsic difficulty, but due to the amount of thought that will need to go into identifying all possible edge cases that could interfere with each function's performance. For example, if a function reads in a geojson-formatted file, can it handle an empty geojson (which throws an error in gdal/fiona)?

One could start by writing tests to cover the "normal operation" cases to ensure functions perform as expected.

Useful references to get started:

• https://docs.pytest.org/en/latest/index.html
• https://docs.python.org/3.6/library/doctest.html (Docstring example testing! This would be great to have)
• https://ilovesymposia.com/2014/10/01/continuous-integration-0-automated-tests-with-pytest/