Fix a typo: unitest -> unittest

[felixonmars]

No description provided.

[codecov]

Codecov Report

Merging #172 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #172   +/-   ##
=======================================
  Coverage   96.21%   96.21%           
=======================================
  Files           1        1           
  Lines        1136     1136           
=======================================
  Hits         1093     1093           
  Misses         43       43

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[tleonhardt]

Thanks for the PR