assertThat(is('a').replaceFrom("yaha", "oo")).isEqualTo("yoohoo");
    assertThat(is('>').replaceFrom("12 > 5", ">")).isEqualTo("12 > 5");
  }

  public void testRetainFrom() {
    assertThat(is('a').retainFrom("bazaar")).isEqualTo("aaa");
    assertThat(is('z').retainFrom("bazaar")).isEqualTo("z");
    assertThat(is('!').retainFrom("!@#$%^&*()-=")).isEqualTo("!");