new RootInputStream(new ByteArrayInputStream(s.getBytes()));
assertEquals(s.charAt(0), (char) is.read());
assertEquals(s.charAt(1), (char) is.read());
assertEquals(s.charAt(2), (char) is.read());
assertEquals(s.charAt(3), (char) is.read());
is.truncate();
assertEquals(-1, is.read());
byte[] buf = new byte[100];
assertEquals(-1, is.read(buf));
assertEquals(-1, is.read(buf, 2, 5));
}