parser.rb

class Parser
  attr_accessor :logger

  def initialize()
    @logger = GELF::Notifier.new
  end

  def log_request( data )
     @logger.notify!(:short_message => 'parsing data', :full_message => data.inspect)
  end

end

parser_spec.rb

describe Parser do
  before(:each) do
    @parser = Parser.new
    @parser.logger = mock('GELF::Notifier')
  end

  it 'should log the incoming data to graylog.' do
    @parser.log_request('ohai2u!')
    @parser.logger.should_receive(:notify!).with({:short_message => 'parsing data', :full_message => 'ohai2u!'})
  end
end