@Test
  public void testPoly1305TestVector4() throws GeneralSecurityException {
    byte[] key =
        Hex.decode("" + "1c9240a5eb55d38af333888604f6b5f0" + "473917c1402b80099dca5cbc207075c0");
    byte[] in =
        Hex.decode(
            ""
                + "2754776173206272696c6c69672c2061"
                + "6e642074686520736c6974687920746f"
                + "7665730a446964206779726520616e64"
                + "2067696d626c6520696e207468652077"
                + "6162653a0a416c6c206d696d73792077"
                + "6572652074686520626f726f676f7665"
                + "732c0a416e6420746865206d6f6d6520"
                + "7261746873206f757467726162652e");
    Truth.assertThat(Poly1305.computeMac(key, in))
        .isEqualTo(Hex.decode("" + "4541669a7eaaee61e708dc7cbcc5eb62"));
  }
Tests against the test vector 4 in Appendix A.3 of RFC 7539.
https://tools.ietf.org/html/rfc7539#appendix-A.3
java_src/src/test/java/com/google/crypto/tink/aead/internal/Poly1305Test.java