Add collision testing test

collision_test.go

+package bbloom
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+)
+
+func TestCollisionRate(t *testing.T) {
+	rand.Seed(time.Now().UTC().UnixNano())
+	N := 1 << 20
+	M := N * 12
+	K := 2
+
+	bl, err := New(float64(M), float64(K))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var buf [64]byte
+	for i := 0; i < N; i++ {
+		_, err := rand.Read(buf[:])
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		bl.Add(buf[:])
+	}
+
+	Ntest := int(1e6)
+	falsePositive := 0
+
+	for i := 0; i < Ntest; i++ {
+		_, err := rand.Read(buf[:])
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if bl.Has(buf[:]) {
+			falsePositive++
+		}
+	}
+
+	t.Logf("false positive ratio: %f", float64(falsePositive)/float64(Ntest))
+}