out.write(buf, 0, 3);

    verify(hashFunction).newHasher();
    verify(hasher).putBytes(buf, 0, 3);
    verifyNoMoreInteractions(hashFunction, hasher);
  }

  public void testHash_hashesCorrectly() throws Exception {
    byte[] buf = new byte[] {'y', 'a', 'm', 's'};
    HashCode expectedHash = Hashing.md5().hashBytes(buf);
    HashingOutputStream out = new HashingOutputStream(Hashing.md5(), buffer);