def total_coverage
      return 0.0 if lines.size.zero?
      ran_lines.size.to_f / lines.size.to_f
    end
def total_coverage
      return 0.0 if lines.size.zero?
      ran_lines.size.to_f / lines.size.to_f
    end
Gives a real number between 0 and 1 indicating how many lines have been
 executed.

 @return [Float] lines executed as a fraction