update instructions for running tests

[jakkdl]

Assumptions

Lots of them, the distinction between the tests can probably be more verbose.

Checklist for All Submissions

• I have added change info to CHANGES.rst
• If this is resolving an issue (needed so future developers can determine if change is still necessary and under what conditions) (can be provided via link to issue with these details): # 1040

[codecov]

Codecov Report

Merging #1045 (eaaeb94) into master (5334722) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1045   +/-   ##
=======================================
  Coverage   86.27%   86.27%           
=======================================
  Files          58       58           
  Lines        5740     5740           
=======================================
  Hits         4952     4952           
  Misses        788      788           

Flag	Coverage Δ
unittests	86.27% <ø> (ø)

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