How do you test two offers at the same time?

You test two lines about the same dish, for example the midday menu and the evening table, each in its own ad. You keep the one that fills the shift you are short of, not the one that only gets more taps. Write the two offers in one line each, with the shift they are for. Both offers say the same thing and nobody knows which one brought the booking. The two lines, the messages from each and which one is switched off.