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
		_ := 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]
	}
}

fn test_rand_f32() {

	mut prev_res := f32(-1.0)
	for _ in 0..rnd_count+1 {
		res := rand.rand_f32(1.0)

		assert res >= 0.0
		assert res <= 1.0

		prev_res = res
	}
}


fn test_rand_f32_in_range() {

	for _ in 0..rnd_count+1 {
		res := rand.rand_f32_in_range(1.0,2.0)

		assert res >= 1.0
		assert res <= 2.0

		// NOTE assert res != prev_res
		// ^- this kind of test can and WILL fail. Random numbers can be the same in subsequent runs
	}
}

fn test_rand_f64() {

	for _ in 0..rnd_count+1 {
		res := rand.rand_f64(1.0)

		assert res >= 0.0
		assert res <= 1.0
	}
}

fn test_rand_f64_in_range() {

	for _ in 0..rnd_count {
		res := rand.rand_f64_in_range(1.0,2.0)

		assert res >= 1.0
		assert res <= 2.0
	}
}