'testforblock' Command not working with 'Items' datatag

In version 1.7.4 you could type:
"testforblock ~ ~1 ~ hopper 8 {Items:[0:{Slot:0b,id:340s,Count:1b,Damage:0s}]}"
to search for a hopper with a book in its first slot.
However, this command no longer works in any of the 1.8 snapshots. It also does not work with chests, droppers or any other items with their own inventory.