### Question:
DefaultMutableWorldState implements MutableWorldState { @Override public Account get(final Address address) { final Hash addressHash = Hash.hash(address); return accountStateTrie .get(addressHash) .map(bytes -> deserializeAccount(address, addressHash, bytes)) .orElse(null); } DefaultMutableWorldState(
      final WorldStateStorage storage, final WorldStatePreimageStorage preimageStorage);  DefaultMutableWorldState(
      final Bytes32 rootHash,
      final WorldStateStorage worldStateStorage,
      final WorldStatePreimageStorage preimageStorage);  DefaultMutableWorldState(final WorldState worldState); @Override Hash rootHash(); @Override MutableWorldState copy(); @Override Account get(final Address address); @Override WorldUpdater updater(); @Override Stream<StreamableAccount> streamAccounts(final Bytes32 startKeyHash, final int limit); @Override int hashCode(); @Override final boolean equals(final Object other); @Override void persist();  }### Answer:
@Test public void containsAccount_AccountDoesNotExist() { final WorldState worldState = createEmpty(); assertThat(worldState.get(ADDRESS)).isNull(); }