Add Unit Tests

[njlyon0]

This is just the scaffolding of the unit testing architecture. Opening this PR now just so this task doesn't slip off of either of our radars. See GitHub Enterprise issue #265 for more details

[njlyon0]

These unit tests look good to me! However, it worries me that some of the GitHub Actions (GHAs) failed on your last push. I did some digging in the GHA details and found this warning/error. Seems like for some reason the lmerTest unit test in stat_extract is having issues.

Doesn't seem like our fault though so my push just now was to check whether commenting out just that bit would cause the GHAs to succeed.

If they do work, I'm happy to green light merging this PR even without that unit test but I'd also support you if you felt like figuring out why it works locally but not on GitHub.

[angelchen7]

Thanks for looking these over, Nick!! The checks were successful locally so I was a bit stumped that the GHAs failed 🤕 getting all these package version to work together in all scenarios can be tricky..

I want to merge the PR but it seems that another GHA is failing due to the example for word_cloud_plot(). The error says " *** caught segfault *** address 0x1, cause 'memory not mapped'" which is very strange and I've never seen that happen before 😖 A quick Google search suggests that it may be due to package versions..

[angelchen7]

In order to pass the GHA checks, I removed word_cloud_plot() example and unit tests. This just didn't seem like something we want to spend a lot of time debugging on right now :/

Then to refine word_cloud_prep() a bit more, I defined more error types for it and wrote some new unit tests to test those errors. By the way, the function already errors out when the text column is provided but it isn't a character type so I did not have to write a new error message for that case. When the text column isn't a character type, tidytext works under-the-hood in the function and spits out an error message that says "Error in check_input(x) : Input must be a character vector of any length or a list of character vectors, each of which has a length of 1."

Everything seem to work locally and the GHA checks all pass so it should be good to go now! I will merge the PR 🎉