lnd_test: wait for state update in completePaymentRequests

Instead of sleeping, we wait for at least one update to one of our
channels. This to make sure the HTLC has actually been committed.

lnd_test.go

@@ -576,10 +576,20 @@ func calcStaticFee(numHTLCs int) btcutil.Amount {
 func completePaymentRequests(ctx context.Context, client lnrpc.LightningClient,
 	paymentRequests []string, awaitResponse bool) error {
 
-	ctx, cancel := context.WithCancel(ctx)
+	// We start by getting the current state of the client's channels. This
+	// is needed to ensure the payments actually have been committed before
+	// we return.
+	ctxt, _ := context.WithTimeout(ctx, defaultTimeout)
+	req := &lnrpc.ListChannelsRequest{}
+	listResp, err := client.ListChannels(ctxt, req)
+	if err != nil {
+		return err
+	}
+
+	ctxc, cancel := context.WithCancel(ctx)
 	defer cancel()
 
-	payStream, err := client.SendPayment(ctx)
+	payStream, err := client.SendPayment(ctxc)
 	if err != nil {
 		return err
 	}
@@ -605,11 +615,40 @@ func completePaymentRequests(ctx context.Context, client lnrpc.LightningClient,
 					resp.PaymentError)
 			}
 		}
-	} else {
+
+		return nil
+	}
+
 	// We are not waiting for feedback in the form of a response, but we
 	// should still wait long enough for the server to receive and handle
-		// the send before cancelling the request.
-		time.Sleep(200 * time.Millisecond)
+	// the send before cancelling the request. We wait for the number of
+	// updates to one of our channels has increased before we return.
+	err = lntest.WaitPredicate(func() bool {
+		ctxt, _ = context.WithTimeout(ctx, defaultTimeout)
+		newListResp, err := client.ListChannels(ctxt, req)
+		if err != nil {
+			return false
+		}
+
+		for _, c1 := range listResp.Channels {
+			for _, c2 := range newListResp.Channels {
+				if c1.ChannelPoint != c2.ChannelPoint {
+					continue
+				}
+
+				// If this channel has an increased numbr of
+				// updates, we assume the payments are
+				// committed, and we can return.
+				if c2.NumUpdates > c1.NumUpdates {
+					return true
+				}
+			}
+		}
+
+		return false
+	}, time.Second*15)
+	if err != nil {
+		return err
 	}
 
 	return nil