Insufficient PRNG testing

[veorq]

Here I'd recommend to test not only the output length but also its content (by checking that the result is identical to the expected one):

sphinx/src/crypto/mod.rs

Lines 62 to 76 in b168f70

	#[cfg(test)]
	mod generating_pseudorandom_bytes {
	use super::*;
	// TODO: 10,000 is the wrong number, @aniap what is correct here?
	#[test]
	fn it_generates_output_of_size_10000() {
	let key: [u8; STREAM_CIPHER_KEY_SIZE] =
	[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
	let iv: [u8; STREAM_CIPHER_KEY_SIZE] = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
	let rand_bytes = generate_pseudorandom_bytes(&key, &iv, 10000);
	assert_eq!(10000, rand_bytes.len());
	}
	}

Also, it's usually better to use input values other than all-zero (or all-some-constant) to detect potential endianness and byte ordering issues.