Simplify tests by using check method for functions that do not change unit.
Simplify tests by using check method for functions that do not change unit.

StuartLittlefair/astropy,bsipocz/astropy,pllim/astropy,bsipocz/astropy,stargaser/astropy,lpsinger/astropy,astropy/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,bsipocz/astropy,saimn/astropy,larrybradley/astropy,StuartLittlefair/astropy,MSeifert04/astropy,astropy/astropy,lpsinger/astropy,larrybradley/astropy,dhomeier/astropy,mhvk/astropy,pllim/astropy,lpsinger/astropy,MSeifert04/astropy,mhvk/astropy,astropy/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy,astropy/astropy,pllim/astropy,larrybradley/astropy,stargaser/astropy,bsipocz/astropy,lpsinger/astropy,saimn/astropy,saimn/astropy,dhomeier/astropy,stargaser/astropy,astropy/astropy,dhomeier/astropy,mhvk/astropy,mhvk/astropy,mhvk/astropy,dhomeier/astropy,stargaser/astropy,aleksandr-bakanov/astropy,MSeifert04/astropy,StuartLittlefair/astropy,lpsinger/astropy,larrybradley/astropy,saimn/astropy,pllim/astropy,saimn/astropy,pllim/astropy,larrybradley/astropy,MSeifert04/astropy,StuartLittlefair/astropy