@Test void utf8_21Bit_brokenLowSurrogate() {
    // https://en.wikipedia.org/wiki/Mahjong_Tiles_(Unicode_block)
    char[] array = "\uD83C\uDC00\uD83C\uDC01".toCharArray();
    array[array.length - 1] = 'c';
    String test = new String(array);
    assertThat(WriteBuffer.utf8SizeInBytes(test))
      .isEqualTo(6);

    byte[] bytes = new byte[6];
    WriteBuffer.wrap(bytes).writeUtf8(test);
    assertThat(new String(bytes, UTF_8))
      .isEqualTo("\uD83C\uDC00?c");
  }
Uses test data and codepoint wrapping trick from okhttp3.FormBodyTest
zipkin/src/test/java/zipkin2/internal/WriteBufferTest.java