move tests from micro repo

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

util/id/id_internal_test.go

@@ -0,0 +1,41 @@
+package id
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestHasNoCollisions(t *testing.T) {
+	tries := 100_000
+	used := make(map[string]bool, tries)
+	for i := 0; i < tries; i++ {
+		id := Must()
+		require.False(t, used[id], "shouldn't return colliding IDs")
+		used[id] = true
+	}
+}
+
+func TestFlatDistribution(t *testing.T) {
+	tries := 100_000
+	alphabet := "abcdefghij"
+	size := 10
+	chars := make(map[rune]int)
+	for i := 0; i < tries; i++ {
+		id := Must(Alphabet(alphabet), Size(size))
+		for _, r := range id {
+			chars[r]++
+		}
+	}
+
+	for _, count := range chars {
+		require.InEpsilon(t, size*tries/len(alphabet), count, .01, "should have flat distribution")
+	}
+}
+
+// Benchmark id generator
+func BenchmarkNanoid(b *testing.B) {
+	for n := 0; n < b.N; n++ {
+		_, _ = New()
+	}
+}