tests: rename vlib/rand/rand_test.v to random_numbers_test.v to fix sporadic CI fails

vlib/rand/random_numbers_test.v

@@ -0,0 +1,58 @@
+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]
+	}
+}