fixes for test cli handling

[fmigneault]

• Add stderr and stdout combined handling for cmd exec during tests
• Handle recurring duplicate process name during tests between test cases

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.66%. Comparing base (e7e3670) to head (781dac1).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #604   +/-   ##
=======================================
  Coverage   85.66%   85.66%           
=======================================
  Files          79       79           
  Lines       18580    18580           
  Branches     2847     2847           
=======================================
  Hits        15917    15917           
  Misses       1926     1926           
  Partials      737      737           

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