added tests for `is_frame_attr_default`
added tests for `is_frame_attr_default`

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