v/vlib/rand/random_numbers_test.v

import rand

const (
	rnd_count = 20
	seeds = [42, 256]
)

fn test_rand_reproducibility() {
	for seed in seeds {
		mut randoms1 := gen_randoms(seed)
		mut randoms2 := gen_randoms(seed)

		assert_randoms_equal(randoms1, randoms2)
	}
}

fn test_rand_r_reproducibility() {
	for seed in seeds {
		mut randoms1 := gen_randoms_r(seed)
		mut randoms2 := gen_randoms_r(seed)

		assert_randoms_equal(randoms1, randoms2)
	}
}

fn test_rand_r_seed_update() {
	seed := 10

	for _ in 0..rnd_count {
		prev_seed := seed
		res := rand.rand_r(&seed)

		assert prev_seed != seed
	}
}

fn gen_randoms(seed int) []int {
	mut randoms := [0].repeat(rnd_count)
	rand.seed(seed)
	for i in 0..rnd_count {
		randoms[i] = rand.next(100)
	}
	return randoms
}

fn gen_randoms_r(seed int) []int {
	mut randoms := [0].repeat(rnd_count)
	for i in 0..rnd_count {
		randoms[i] = rand.rand_r(&seed)
	}
	return randoms
}

fn assert_randoms_equal(r1, r2 []int) {
	for i in 0..rnd_count {
		assert r1[i] == r2[i]
	}
}