The command...
/testfor @e[type=Item] {Item:{id:minecraft:nether_star}}
...would ordinarily work, but with the new NBT tag parsing, now I get:
Data tag parsing failed: Expected '}' but got ':' at {Item:{id:minecraft:<--[HERE]
The minecraft: part IS required, since running...
/testfor @e[type=Item] {Item:{id:nether_star}}
...with a nether star item floating nearby fails with...
item.item.netherStar did not match the required data structure
The same goes for other items.
Aaaaand, unfortunately, this breaks a LOT of stuff on my map.
Use