Add dims keywords to some tests

[mcabbott]

This should silence some warnings in the tests. The functions are in MLUtils but probably fine to keep their tests.

[codecov-commenter]

Codecov Report

Merging #1906 (15f06c9) into master (9755d57) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1906   +/-   ##
=======================================
  Coverage   86.23%   86.23%           
=======================================
  Files          18       18           
  Lines        1438     1438           
=======================================
  Hits         1240     1240           
  Misses        198      198           

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