lib/rand: Break out random functions into separate package

The intention for this package is to provide a combination of the
security of crypto/rand and the convenience of math/rand. It should be
the first choice of random data unless ultimate performance is required
and the usage is provably irrelevant from a security standpoint.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3186

lib/rand/random_test.go

@@ -0,0 +1,63 @@
+// Copyright (C) 2014 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package rand
+
+import "testing"
+
+func TestSeedFromBytes(t *testing.T) {
+	// should always return the same seed for the same bytes
+	tcs := []struct {
+		bs []byte
+		v  int64
+	}{
+		{[]byte("hello world"), -3639725434188061933},
+		{[]byte("hello worlx"), -2539100776074091088},
+	}
+
+	for _, tc := range tcs {
+		if v := SeedFromBytes(tc.bs); v != tc.v {
+			t.Errorf("Unexpected seed value %d != %d", v, tc.v)
+		}
+	}
+}
+
+func TestRandomString(t *testing.T) {
+	for _, l := range []int{0, 1, 2, 3, 4, 8, 42} {
+		s := String(l)
+		if len(s) != l {
+			t.Errorf("Incorrect length %d != %d", len(s), l)
+		}
+	}
+
+	strings := make([]string, 1000)
+	for i := range strings {
+		strings[i] = String(8)
+		for j := range strings {
+			if i == j {
+				continue
+			}
+			if strings[i] == strings[j] {
+				t.Errorf("Repeated random string %q", strings[i])
+			}
+		}
+	}
+}
+
+func TestRandomInt64(t *testing.T) {
+	ints := make([]int64, 1000)
+	for i := range ints {
+		ints[i] = Int64()
+		for j := range ints {
+			if i == j {
+				continue
+			}
+			if ints[i] == ints[j] {
+				t.Errorf("Repeated random int64 %d", ints[i])
+			}
+		}
+	}
+}