# File test/test_rrdtool.rb, line 24
  def create_file
    @start = Time.now.to_i - 1
    @step = 300
    @r.create @step, @start, [ "DS:a:GAUGE:#{2*@step}:0:1", 
      "DS:b:GAUGE:#{2*@step}:-10:10",
      "RRA:AVERAGE:0.5:1:300", 
      "RRA:LAST:0.5:1:10" ]
  end