Fix tests for concatenating PertConstRows, etc.

[dlfivefifty]

@DanielVandH this is to fix the broken tests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.67%. Comparing base (8dfbaf6) to head (3c713ee).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #227      +/-   ##
==========================================
+ Coverage   89.31%   89.67%   +0.35%     
==========================================
  Files          10       10              
  Lines        1142     1143       +1     
==========================================
+ Hits         1020     1025       +5     
+ Misses        122      118       -4     

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