TST: Ensure IDs are unique

[bashtage]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.54%. Comparing base (1cd9905) to head (b470a94).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #847   +/-   ##
=======================================
  Coverage   99.54%   99.54%           
=======================================
  Files          78       78           
  Lines       15817    15817           
  Branches     1294     1294           
=======================================
  Hits        15745    15745           
  Misses         38       38           
  Partials       34       34           

Flag	Coverage Δ
adder	99.50% <100.00%> (ø)
subtractor	99.50% <100.00%> (ø)

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