In the latest snapshot furnaces do not get reset when the fuel runs out. The issue is they also do not reset if the item is swapped out while the furnace is smelting. Also, if the furnace runs out of fuel in the middle of a smelting process, the item can be removed and changed without the furnace resetting.
Linked issues
Comments 3
Affects 1.7.5.
Note: when the fuel runs out the progress arrow resets, but when more fuel is added it returns to it's previous completion state.
Is this still a concern in the current Minecraft version 1.7.5 / Launcher version 1.3.11 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.