add some tests to ntp timestamp conversion

Relates to #15

packetizer.go

@@ -42,10 +42,10 @@ func NewPacketizer(mtu int, pt uint8, ssrc uint32, payloader Payloader, sequence
 	}
 }
 
-func toNtpTime(t time.Time) int64 {
-	var s int64
-	var f int64
-	u := t.UnixNano()
+func toNtpTime(t time.Time) uint64 {
+	var s uint64
+	var f uint64
+	u := uint64(t.UnixNano())
 	s = u / 1e9
 	s += 0x83AA7E80 //offset in seconds between unix epoch and ntp epoch
 	f = u % 1e9

packetizer_test.go

@@ -0,0 +1,26 @@
+package rtp
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNtpConversion(t *testing.T) {
+	loc := time.FixedZone("UTC-5", -5*60*60)
+
+	tests := []struct {
+		t time.Time
+		n uint64
+	}{
+		{t: time.Date(1985, time.June, 23, 4, 0, 0, 0, loc), n: 0xa0c65b1000000000},
+		{t: time.Date(1999, time.December, 31, 23, 59, 59, 500000, loc), n: 0xbc18084f0020c49b},
+		{t: time.Date(2019, time.March, 27, 13, 39, 30, 8675309, loc), n: 0xe04641e202388b88},
+	}
+
+	for _, in := range tests {
+		out := toNtpTime(in.t)
+		assert.Equal(t, in.n, out)
+	}
+}