v/vlib/rand/random_identifiers_test.v

import time
import rand

// uuid_v4:
fn test_rand_uuid_v4() {
	uuid1 := rand.uuid_v4()
	uuid2 := rand.uuid_v4()
	uuid3 := rand.uuid_v4()
	assert uuid1 != uuid2
	assert uuid1 != uuid3
	assert uuid2 != uuid3
	assert uuid1.len == 36
	assert uuid2.len == 36
	assert uuid3.len == 36
	assert uuid1[14] == `4`
	assert uuid2[14] == `4`
	assert uuid3[14] == `4`
}

// ulids:
fn test_ulids_are_unique() {
	ulid1 := rand.ulid()
	ulid2 := rand.ulid()
	ulid3 := rand.ulid()
	assert ulid1.len == 26
	assert ulid2.len == 26
	assert ulid3.len == 26
	assert ulid1 != ulid2
	assert ulid1 != ulid3
	assert ulid2 != ulid3
}

fn test_ulids_max_start_character_is_ok() {
	ulid1 := rand.ulid()
	// the largest valid ULID encoded in Base32 is 7ZZZZZZZZZZZZZZZZZZZZZZZZZ
	assert (int(ulid1[0]) - 48) <= 7
}

fn test_ulids_generated_in_the_same_millisecond_have_the_same_prefix() {
	t := time.utc().unix_time_milli()
	mut ulid1 := ''
	mut ulid2 := ''
	mut ulid3 := ''    
	ulid1 = rand.ulid_at_millisecond(t)
	ulid2 = rand.ulid_at_millisecond(t)
	ulid3 = rand.ulid_at_millisecond(t)
	ulid1_prefix := ulid1[0..10]
	ulid2_prefix := ulid2[0..10]
	ulid3_prefix := ulid3[0..10]
	assert ulid1_prefix == ulid2_prefix
	assert ulid1_prefix == ulid3_prefix
}

fn test_ulids_should_be_lexicographically_ordered_when_not_in_same_millisecond() {
	ulid1 := rand.ulid()
	time.sleep_ms(1)
	ulid2 := rand.ulid()
	time.sleep_ms(1)
	ulid3 := rand.ulid()
	mut all := [ulid3, ulid2, ulid1]
	// eprintln('all before: $all')
	all.sort()
	// eprintln('all  after: $all')
	s1 := all[0]
	s2 := all[1]
	s3 := all[2]
	assert s1 == ulid1
	assert s2 == ulid2
	assert s3 == ulid3
}