add tests for 'previous_slide' and 'next_slide'
add tests for 'previous_slide' and 'next_slide'

kivy/kivy,kivy/kivy,rnixx/kivy,matham/kivy,inclement/kivy,akshayaurora/kivy,rnixx/kivy,inclement/kivy,kivy/kivy,rnixx/kivy,matham/kivy,matham/kivy,matham/kivy,akshayaurora/kivy,inclement/kivy,akshayaurora/kivy