public void writeAscii(CharSequence v) {
    for (int i = 0, length = v.length(); i < length; i++) {
      writeByte(v.charAt(i) & 0xff);
    }
  }
@Test void writeAscii_long() {
    assertThat(writeAscii(-1005656679588439279L))
        .isEqualTo("-1005656679588439279");
    assertThat(writeAscii(0L))
        .isEqualTo("0");
    assertThat(writeAscii(-9223372036854775808L /* Long.MIN_VALUE */))
        .isEqualTo("-9223372036854775808");
    assertThat(writeAscii(123456789L))
        .isEqualTo("123456789");
  }