@Test
  public void testX25519PublicFromPrivateThrowsIllegalArgExWhenPrivateKeyIsGreaterThan32Bytes() {
    publicFromPrivateHelper(33);
  }
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