assertFullyRead(reader);

    // reset to the mark and then read the rest
    reader.reset();
    assertEquals(string.substring(5), readFully(reader));
    assertFullyRead(reader);
  }

  public void testIllegalArguments() throws IOException {
    CharSequenceReader reader = new CharSequenceReader("12345");

    char[] buf = new char[10];
    assertThrows(IndexOutOfBoundsException.class, () -> reader.read(buf, 0, 11));