sweepbatcher: test that empty batches won't prevent startup

sweepbatcher/sweep_batcher.go

@@ -153,6 +153,10 @@ type Batcher struct {
 	// quit signals that the batch must stop.
 	quit chan struct{}
 
+	// initDone is a channel that is closed when the batcher has been
+	// initialized.
+	initDone chan struct{}
+
 	// wallet is the wallet kit client that is used by batches.
 	wallet lndclient.WalletKitClient
 
@@ -200,6 +204,7 @@ func NewBatcher(wallet lndclient.WalletKitClient,
 		sweepReqs:        make(chan SweepRequest),
 		errChan:          make(chan error, 1),
 		quit:             make(chan struct{}),
+		initDone:         make(chan struct{}),
 		wallet:           wallet,
 		chainNotifier:    chainNotifier,
 		signerClient:     signerClient,
@@ -239,6 +244,9 @@ func (b *Batcher) Run(ctx context.Context) error {
 		}
 	}
 
+	// Signal that the batcher has been initialized.
+	close(b.initDone)
+
 	for {
 		select {
 		case sweepReq := <-b.sweepReqs:

sweepbatcher/sweep_batcher_test.go

@@ -3,6 +3,7 @@ package sweepbatcher
 import (
 	"context"
 	"errors"
+	"sync"
 	"testing"
 	"time"
 
@@ -1028,3 +1029,85 @@ func TestGetFeePortionForSweep(t *testing.T) {
 		})
 	}
 }
+
+// TestRestoringEmptyBatch tests that the batcher can be restored with an empty
+// batch.
+func TestRestoringEmptyBatch(t *testing.T) {
+	defer test.Guard(t)()
+
+	lnd := test.NewMockLnd()
+	ctx, cancel := context.WithCancel(context.Background())
+
+	store := loopdb.NewStoreMock(t)
+
+	batcherStore := NewStoreMock()
+	_, err := batcherStore.InsertSweepBatch(ctx, &dbBatch{})
+	require.NoError(t, err)
+
+	batcher := NewBatcher(lnd.WalletKit, lnd.ChainNotifier, lnd.Signer,
+		testMuSig2SignSweep, nil, lnd.ChainParams, batcherStore, store)
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	var runErr error
+	go func() {
+		defer wg.Done()
+		runErr = batcher.Run(ctx)
+	}()
+
+	// Wait for the batcher to be initialized.
+	<-batcher.initDone
+
+	// Create a sweep request.
+	sweepReq := SweepRequest{
+		SwapHash: lntypes.Hash{1, 1, 1},
+		Value:    111,
+		Outpoint: wire.OutPoint{
+			Hash:  chainhash.Hash{1, 1},
+			Index: 1,
+		},
+		Notifier: &dummyNotifier,
+	}
+
+	swap := &loopdb.LoopOutContract{
+		SwapContract: loopdb.SwapContract{
+			CltvExpiry:      111,
+			AmountRequested: 111,
+		},
+
+		SwapInvoice: swapInvoice,
+	}
+
+	err = store.CreateLoopOut(ctx, sweepReq.SwapHash, swap)
+	require.NoError(t, err)
+	store.AssertLoopOutStored()
+
+	// Deliver sweep request to batcher.
+	batcher.sweepReqs <- sweepReq
+
+	// Since a batch was created we check that it registered for its primary
+	// sweep's spend.
+	<-lnd.RegisterSpendChannel
+
+	// Once batcher receives sweep request it will eventually spin up a
+	// batch.
+	require.Eventually(t, func() bool {
+		// Make sure that the sweep was stored and we have exactly one
+		// active batch.
+		return batcherStore.AssertSweepStored(sweepReq.SwapHash) &&
+			len(batcher.batches) == 1
+	}, test.Timeout, eventuallyCheckFrequency)
+
+	// Make sure we have only one batch stored (as we dropped the dormant
+	// one).
+	batches, err := batcherStore.FetchUnconfirmedSweepBatches(ctx)
+	require.NoError(t, err)
+	require.Len(t, batches, 1)
+
+	// Now make it quit by canceling the context.
+	cancel()
+	wg.Wait()
+
+	checkBatcherError(t, runErr)
+}