Unit test the units class (#14827)
Unit test the units class (#14827)

andrsd/moose,sapitts/moose,bwspenc/moose,jessecarterMOOSE/moose,dschwen/moose,lindsayad/moose,andrsd/moose,nuclear-wizard/moose,bwspenc/moose,dschwen/moose,idaholab/moose,jessecarterMOOSE/moose,dschwen/moose,laagesen/moose,sapitts/moose,SudiptaBiswas/moose,idaholab/moose,idaholab/moose,harterj/moose,laagesen/moose,lindsayad/moose,milljm/moose,SudiptaBiswas/moose,andrsd/moose,harterj/moose,nuclear-wizard/moose,SudiptaBiswas/moose,nuclear-wizard/moose,dschwen/moose,bwspenc/moose,bwspenc/moose,milljm/moose,SudiptaBiswas/moose,andrsd/moose,laagesen/moose,lindsayad/moose,lindsayad/moose,harterj/moose,lindsayad/moose,harterj/moose,nuclear-wizard/moose,sapitts/moose,dschwen/moose,sapitts/moose,laagesen/moose,jessecarterMOOSE/moose,harterj/moose,SudiptaBiswas/moose,laagesen/moose,andrsd/moose,sapitts/moose,milljm/moose,jessecarterMOOSE/moose,idaholab/moose,jessecarterMOOSE/moose,idaholab/moose,milljm/moose,bwspenc/moose,milljm/moose