Curve 25519 is one of the most widely used ECC methods and is defined in [RFC 7748]. This page will take the two vectors defined in the RFC, and check the output. [secp256k1 barebones][P256 barebones][P521 barebones][Curve 25519 barebones]. With X25519, we have an input u-coordinate value (the x-value) and a scalar value, and we get an output u-coordinate. The vectors are:
Input scalar as a number (base 10): 31029842492115040904895560451863089656472772604678260265531221036453811406496 Input u-coordinate as a number (base 10): 34426434033919594451155107781188821651316167215306631574996226621102155684838 Output u-coordinate: c3da55379de9c6908e94ea4df28d084f32eccf03491c71f754b4075577a28552