add missing test dependency

[KristofferC]

No description provided.

[codecov-io]

Codecov Report

Merging #426 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #426   +/-   ##
=======================================
  Coverage   85.89%   85.89%           
=======================================
  Files          10       10           
  Lines         468      468           
=======================================
  Hits          402      402           
  Misses         66       66

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