Detecting items in a Dropper
Count and Slot are both bytes, so need a 'b' after them. You also need to specify the full item name:
/testforblock ~ ~-1 ~ dropper 1 {Items:[{Slot:0b,id:minecraft:stone,Count:64b}]}
Count and Slot are both bytes, so need a 'b' after them. You also need to specify the full item name:
/testforblock ~ ~-1 ~ dropper 1 {Items:[{Slot:0b,id:minecraft:stone,Count:64b}]}