add rand package, utilities for math/rand.

rand/rand_test.go

@@ -0,0 +1,74 @@
+package rand
+
+import (
+	"fmt"
+	mrand "math/rand"
+	"testing"
+)
+
+func TestCryptoUint64(t *testing.T) {
+	n1, err := CryptoUint64()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	n2, err := CryptoUint64()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// This has such a low chance of occurring that it's likely to be
+	// indicative of a bad CSPRNG.
+	if n1 == n2 {
+		t.Fatalf("repeated random uint64s: %d", n1)
+	}
+}
+
+func TestIntn(t *testing.T) {
+	expected := []int{3081, 4887, 4847, 1059, 3081}
+	mrand.Seed(1)
+	for i := 0; i < 5; i++ {
+		n := Intn2(1000, 5000)
+
+		if n != expected[i] {
+			fmt.Printf("invalid sequence at %d: expected %d, have %d", i, expected[i], n)
+		}
+	}
+}
+
+func TestSeed(t *testing.T) {
+	seed1, err := Seed()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var seed2 uint64
+	n1 := Int()
+	tries := 0
+
+	for {
+		seed2, err = Seed()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if seed1 != seed2 {
+			break
+		}
+
+		tries++
+
+		if tries > 3 {
+			t.Fatal("can't generate two unique seeds")
+		}
+	}
+
+	n2 := Int()
+
+	// Again, this not impossible, merely statistically improbably and a
+	// potential canary for RNG issues.
+	if n1 == n2 {
+		t.Fatalf("repeated integers fresh from two unique seeds: %d/%d -> %d",
+			seed1, seed2, n1)
+	}
+}