added test case for #537
added test case for #537

jfhg/Nim,russpowers/Nim,jfhg/Nim,mbaulch/Nim,jfhg/Nim,dom96/Nim,jfhg/Nim,tulayang/Nim,mbaulch/Nim,haiodo/Nim,russpowers/Nim,singularperturbation/Nim,dom96/Nim,russpowers/Nim,dom96/Nim,mbaulch/Nim,russpowers/Nim,dom96/Nim,jfhg/Nim,singularperturbation/Nim,haiodo/Nim,tulayang/Nim,haiodo/Nim,tulayang/Nim,singularperturbation/Nim,jfhg/Nim,russpowers/Nim,haiodo/Nim,haiodo/Nim,mbaulch/Nim,dom96/Nim,mbaulch/Nim,tulayang/Nim,singularperturbation/Nim,haiodo/Nim,jfhg/Nim,russpowers/Nim,singularperturbation/Nim,russpowers/Nim,mbaulch/Nim,mbaulch/Nim,singularperturbation/Nim,tulayang/Nim,dom96/Nim,haiodo/Nim,singularperturbation/Nim,dom96/Nim,tulayang/Nim