add missing test dependency

[KristofferC]

No description provided.

[codecov]

Codecov Report

Merging #12 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #12   +/-   ##
=======================================
  Coverage   89.34%   89.34%           
=======================================
  Files          12       12           
  Lines         169      169           
=======================================
  Hits          151      151           
  Misses         18       18

---

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[codecov]

Codecov Report

Merging #12 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #12   +/-   ##
=======================================
  Coverage   89.34%   89.34%           
=======================================
  Files          12       12           
  Lines         169      169           
=======================================
  Hits          151      151           
  Misses         18       18

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 27dfb5e...e851ed5. Read the comment docs.

[tkoolen]

Thanks!