@Test
public void testModify() throws Exception {

    // replace one character with whitespace
    assertModify(" ", "a\uD8FFb", "a b", "1.0", 8192, false);
    // replace two characters with whitespace
    assertModify(" ", "a\uD8FFb\uD8FFc", "a b c", "1.0", 8192, false);
    // delete two characters
    assertModify("", "a\uD8FFb\uD8FFc", "abc", "1.0", 8192, false);
    // delete two characters (a newline in the string)
    assertModify("", "a\uD8FF\n\uD8FFc", "a\nc", "1.0", 8192, false);
}