When you execute a data transfer activity in Test mode, no offer fulfillment takes place. When doing so in Production mode, offer fulfillment takes place – e.g. data extract files are created, or data written to the realtime cache. However, no records are inserted into Offer History or Offer History Meta.
Note that, when you execute a data transfer activity in a recurring workflow that is configured to produce a single workflow instance, or when you execute it downstream from an interactive activity, all qualifying records are targeted with the offer, rather than just new records.