@Test
  public void testPublicFromPrivateWithRfcTestVectors() throws Exception {
    byte[] out =
        X25519.publicFromPrivate(
            Hex.decode("77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a"));
    assertEquals(
        "8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a", Hex.encode(out));

    out =
        X25519.publicFromPrivate(
            Hex.decode("5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb"));
    assertEquals(
        "de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f", Hex.encode(out));
  }
Tests against the test vectors in Section 6.1 of RFC 7748. https://tools.ietf.org/html/rfc7748
java_src/src/test/java/com/google/crypto/tink/subtle/X25519Test.java