Optional<Long> sizeIfKnown = source.sizeIfKnown();
    if (sizeIfKnown.isPresent()) {
      assertEquals(expected.length, (long) sizeIfKnown.get());
    }
  }

  public void testContentEquals() throws IOException {
    assertTrue(
        source.contentEquals(
            new ByteSource() {
              @Override
              public InputStream openStream() throws IOException {