Split up authToken unit test for readability

[hkamm123]

This PR makes two contributions:

1. splits up a unit test ("Unique authToken each login") into two: one that tests authToken uniqueness across multiple logins, and another that tests individual authToken validity across multiple logins/logouts (the previous version of the test was testing this, but did not declare so).
2. updates the order of the tests.

[mewilker]

I was worried this would miss an edge case, but now that I look at it closer I see that it shouldn't! Something we could do that could potentially help readablility is make a function for the double login, but I don't think that's completely necessary.