test_spec.rb

require 'spec_helper'

class ProcessLogFiles
  def start
    # for log in logfiles
      LogFile.new.process #log
    # end
  end
end

class LogFile
  def process
    # for line in log
    #   if some condition is met
          LogMail.new.send # or some other meth with no side-effect
    #   end
    # end
  end
end

class LogMail
  def send
  end
end

describe "testing nest" do
  it "should show that a function was called" do
    LogMail.any_instance.stubs(:send).runs { $ran_meth = true }
    ProcessLogFiles.new.start
    $ran_meth.should == true
  end
end