add test for timestamps

internal/experiment/openvpn/openvpn.go

@@ -155,17 +155,7 @@ func (m *Measurer) connectAndHandshake(
 	handshakeEvents := handshakeTracer.Trace()
 	port, _ := strconv.Atoi(endpoint.Port)
 
-	var (
-		tFirst        float64
-		tLast         float64
-		bootstrapTime float64
-	)
-
-	if len(handshakeEvents) > 0 {
-		tFirst = handshakeEvents[0].AtTime
-		tLast = handshakeEvents[len(handshakeEvents)-1].AtTime
-		bootstrapTime = tLast - tFirst
-	}
+	t0, t, bootstrapTime := TimestampsFromHandshake(handshakeEvents)
 
 	return &SingleConnection{
 		TCPConnect: trace.FirstTCPConnectOrNil(),
@@ -182,15 +172,29 @@ func (m *Measurer) connectAndHandshake(
 				Auth:        openvpnConfig.OpenVPNOptions().Auth,
 				Compression: string(openvpnConfig.OpenVPNOptions().Compress),
 			},
-			T0:            tFirst,
-			T:             tLast,
+			T0:            t0,
+			T:             t,
 			Tags:          []string{},
 			TransactionID: index,
 		},
 		NetworkEvents: handshakeEvents,
 	}
 }
 
+func TimestampsFromHandshake(events []*vpntracex.Event) (float64, float64, float64) {
+	var (
+		t0       float64
+		t        float64
+		duration float64
+	)
+	if len(events) > 0 {
+		t0 = events[0].AtTime
+		t = events[len(events)-1].AtTime
+		duration = t - t0
+	}
+	return t0, t, duration
+}
+
 // FetchProviderCredentials will extract credentials from the configuration we gathered for a given provider.
 func (m *Measurer) FetchProviderCredentials(
 	ctx context.Context,

internal/experiment/openvpn/openvpn_test.go

@@ -253,3 +253,18 @@ func TestSuccess(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestTimestampsFromHandshake(t *testing.T) {
+	events := []*vpntracex.Event{{AtTime: 0}, {AtTime: 1}, {AtTime: 2}}
+	t0, tlast, duration := openvpn.TimestampsFromHandshake(events)
+	if t0 != 0 {
+		t.Fatal("expected t0 == 0")
+	}
+	if tlast != 2.0 {
+		t.Fatal("expected t0 == 2")
+	}
+	if duration != 2 {
+		t.Fatal("expected duration == 2")
+	}
+
+}