Correct tests for heaviside.
Correct tests for heaviside.

kelle/astropy,lpsinger/astropy,astropy/astropy,joergdietrich/astropy,lpsinger/astropy,kelle/astropy,dhomeier/astropy,larrybradley/astropy,dhomeier/astropy,bsipocz/astropy,saimn/astropy,astropy/astropy,funbaker/astropy,saimn/astropy,larrybradley/astropy,StuartLittlefair/astropy,pllim/astropy,larrybradley/astropy,MSeifert04/astropy,DougBurke/astropy,lpsinger/astropy,saimn/astropy,stargaser/astropy,bsipocz/astropy,mhvk/astropy,joergdietrich/astropy,funbaker/astropy,saimn/astropy,AustereCuriosity/astropy,joergdietrich/astropy,saimn/astropy,dhomeier/astropy,pllim/astropy,aleksandr-bakanov/astropy,bsipocz/astropy,mhvk/astropy,AustereCuriosity/astropy,lpsinger/astropy,DougBurke/astropy,joergdietrich/astropy,AustereCuriosity/astropy,mhvk/astropy,kelle/astropy,mhvk/astropy,DougBurke/astropy,StuartLittlefair/astropy,funbaker/astropy,aleksandr-bakanov/astropy,bsipocz/astropy,MSeifert04/astropy,funbaker/astropy,stargaser/astropy,dhomeier/astropy,lpsinger/astropy,astropy/astropy,stargaser/astropy,pllim/astropy,aleksandr-bakanov/astropy,astropy/astropy,DougBurke/astropy,astropy/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,stargaser/astropy,AustereCuriosity/astropy,kelle/astropy,kelle/astropy,joergdietrich/astropy,pllim/astropy,MSeifert04/astropy,larrybradley/astropy,pllim/astropy,MSeifert04/astropy,StuartLittlefair/astropy,larrybradley/astropy,AustereCuriosity/astropy,dhomeier/astropy,StuartLittlefair/astropy,mhvk/astropy