in plasma-store/src/tests.rs [236:249]
fn plasma_client_create_then_seal_error() {
let pc = build_client();
// put object into the store
let oid = ObjectId::rand();
let data = [1u8, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
pc.create_and_seal(oid.clone(), &data, &[]).unwrap();
// get the object from the store
let mut ob = pc.get(oid, 5).unwrap().unwrap();
// trying to seal this object should result in an error
assert!(ob.seal().is_err());
}