For the booster stage of Falcon 9, test landings after a full flight profile are relatively frequent. SpaceX can try those on each CRS mission to the ISS, and in theory, any other launch that wouldn't require complete booster stage burnout to exhaustion, such as higher energy trajectories to GEO or beyond. And they were using Grasshopper and F9R Dev1 for development VTVL test flights.
For Dragon and Crew Dragon spacecraft powered landing however, while they can of course try short flight profile tests relatively easily, and they will have to complete at the minimum one more test landing of Crew Dragon during the in-flight abort for the CCDev contract with NASA, the latter will be a parachuted descent. And so far, same goes for CRS missions with Dragon splashing somewhere in the Pacific west of California.
So when will SpaceX be able to test full flight profile powered descent and landing of Dragon / Crew Dragon?