A method of flow testing can include dispensing at least one solid material and at least one liquid into each of multiple wells in a filter plate, and allowing the liquid to flow from the filter plate only by force of gravity. A flow testing system can include a multiple well filter plate, each of the wells having disposed therein a selected combination of formation particles, a fracturing fluid composition and a liquid hydrocarbon, and a collection plate vertically below the filter plate. The fracturing fluid composition and the liquid hydrocarbon flow from the filter plate to the collection plate only by force of gravity.