[MISC]: Improve Testing (Coverage and Cross-Package Integration)

[jthielen]

What is your issue?

A few good comments came up in #14 about improving our tests, so re-recording them here so as to not loose track of them:

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Looks good to me! 👍🏽

The code coverage for postprocess.py is relatively low but we can address this in a separate PR

Originally posted by @andersy005 in #14 (review)

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Unfortunately, with the new changes metpy.parse_cf() breaks for me as it seems to try to cast XTIME to meters. I am getting a DimensionalityError

var = var.metpy.convert_coordinate_units(coord_name, 'meters')
DimensionalityError: Cannot convert from 'dimensionless' (dimensionless) to 'meter' ([length])
I tried adding some units attributes and setting the coordinates kwarg of metpy.parse_cf(), but nothing helped. Does anybody have a hint as to what is happening here?

@lpilz: This sound like a good test to add.

Originally posted by @kmpaul in #14 (comment)