Write test for If else condition in Rsepc rails 5 in model

I just started learning testing through Rsepc in Rails how to write rsepc test for demo method in School model and please suggest me some good tutorial for rsepc testing for models,controllers,jobs,channels.

class School < ApplicationRecord
    def demo
        if status == 'pro'
            #do something
        elsif status == 'free'
            #do something
        else
            #do something
        end
    end
end

Thanks in advance.