class SimpleCov::Formatter::MultiFormatter

output formats (HTML + JSON, etc.) in a single run.
Wraps multiple formatters so SimpleCov.formatter can drive several

def self.new(formatters = nil) 

def self.new(formatters = nil)
  Class.new do
    define_method :formatters do
      @formatters ||= Array(formatters)
    end
    include InstanceMethods
  end
end