When stop is nil or omitted to Numeric#step, it should be set to infinity_value, and sign would be same with step.
When stop is nil or omitted to Numeric#step,
it should be set to infinity_value,
and sign would be same with step.

I don't know a better way the cover this in spec though

eregon/rubyspec,sgarciac/spec,sgarciac/spec,sgarciac/spec,ruby/rubyspec,ruby/spec,ruby/rubyspec,ruby/spec,eregon/rubyspec,ruby/spec,eregon/rubyspec,nobu/rubyspec,nobu/rubyspec,nobu/rubyspec