Possible async issues with tests

[solsson]

The jest suite passes with #14, but I'm getting the following warnings:

Jest did not exit one second after the test run has completed.
This usually means that there are asynchronous operations that weren't stopped in your tests. Consider running Jest with --detectOpenHandles to troubleshoot this issue.

Jest has detected the following 1 open handle potentially keeping Jest from exiting:
● ZLIB