introduce separate congestion debug interface to simplify mocking

congestion/cubic_sender.go

@@ -62,7 +62,7 @@ type cubicSender struct {
 }
 
 // NewCubicSender makes a new cubic sender
-func NewCubicSender(clock Clock, rttStats *RTTStats, reno bool, initialCongestionWindow, initialMaxCongestionWindow protocol.PacketNumber) SendAlgorithm {
+func NewCubicSender(clock Clock, rttStats *RTTStats, reno bool, initialCongestionWindow, initialMaxCongestionWindow protocol.PacketNumber) SendAlgorithmWithDebugInfo {
 	return &cubicSender{
 		rttStats:                   rttStats,
 		initialCongestionWindow:    initialCongestionWindow,

congestion/cubic_sender_test.go

@@ -25,7 +25,7 @@ func (c *mockClock) Advance(d time.Duration) {
 
 var _ = Describe("Cubic Sender", func() {
 	var (
-		sender            congestion.SendAlgorithm
+		sender            congestion.SendAlgorithmWithDebugInfo
 		clock             mockClock
 		bytesInFlight     protocol.ByteCount
 		packetNumber      protocol.PacketNumber

congestion/interface.go

@@ -11,7 +11,6 @@ type SendAlgorithm interface {
 	OnPacketSent(sentTime time.Time, bytesInFlight protocol.ByteCount, packetNumber protocol.PacketNumber, bytes protocol.ByteCount, isRetransmittable bool) bool
 	GetCongestionWindow() protocol.ByteCount
 	OnCongestionEvent(rttUpdated bool, bytesInFlight protocol.ByteCount, ackedPackets PacketVector, lostPackets PacketVector)
-	BandwidthEstimate() Bandwidth
 	SetNumEmulatedConnections(n int)
 	OnRetransmissionTimeout(packetsRetransmitted bool)
 	OnConnectionMigration()
@@ -19,9 +18,15 @@ type SendAlgorithm interface {
 
 	// Experiments
 	SetSlowStartLargeReduction(enabled bool)
+}
+
+type SendAlgorithmWithDebugInfo interface {
+	SendAlgorithm
+	BandwidthEstimate() Bandwidth
 
 	// Stuff only used in testing
 	// TODO: Maybe make CubicSender public and typeassert in tests?
+
 	HybridSlowStart() *HybridSlowStart
 	SlowstartThreshold() protocol.PacketNumber
 	RenoBeta() float32