byte[] buf = new byte[4];
    int numOfByteRead = in.read(buf, 0, buf.length);
    assertEquals(2, numOfByteRead);

    assertEquals(expectedHash, in.hash());
  }

  public void testChecksForNull() throws Exception {
    NullPointerTester tester = new NullPointerTester();

    tester.testAllPublicInstanceMethods(new HashingInputStream(Hashing.md5(), buffer));