Fix unhandled promise rejection in tests

[JustinBeckwith]

Fixes #<issue_number_goes_here> (it's a good idea to open an issue first for discussion)

• Tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[codecov]

Codecov Report

Merging #180 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #180   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           2      2           
  Lines          37     37           
=====================================
  Hits           37     37

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