multi: move WaitPredicate, WaitNoError, WaitInvariant to lntest/wait

breacharbiter_test.go

@@ -29,7 +29,7 @@ import (
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/keychain"
-	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/shachain"
@@ -1537,7 +1537,7 @@ func assertBrarCleanup(t *testing.T, brar *breachArbiter,
 
 	t.Helper()
 
-	err := lntest.WaitNoError(func() error {
+	err := wait.NoError(func() error {
 		isBreached, err := brar.IsBreached(chanPoint)
 		if err != nil {
 			return err

discovery/gossiper_test.go

@@ -24,7 +24,7 @@ import (
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/lnpeer"
-	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -3432,7 +3432,7 @@ func TestSendChannelUpdateReliably(t *testing.T) {
 
 	// Since the messages above are now deemed as stale, they should be
 	// removed from the message store.
-	err = lntest.WaitNoError(func() error {
+	err = wait.NoError(func() error {
 		msgs, err := ctx.gossiper.cfg.MessageStore.Messages()
 		if err != nil {
 			return fmt.Errorf("unable to retrieve pending "+
@@ -3491,7 +3491,7 @@ func assertBroadcastMsg(t *testing.T, ctx *testCtx,
 	// predicate returns true for any of the messages, so we'll continue to
 	// retry until either we hit our timeout, or it returns with no error
 	// (message found).
-	err := lntest.WaitNoError(func() error {
+	err := wait.NoError(func() error {
 		select {
 		case msg := <-ctx.broadcastedMessage:
 			return predicate(msg.msg)

discovery/reliable_sender_test.go

@@ -8,7 +8,7 @@ import (
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/davecgh/go-spew/spew"
 	"github.com/lightningnetwork/lnd/lnpeer"
-	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
@@ -244,7 +244,7 @@ func TestReliableSenderStaleMessages(t *testing.T) {
 	// message store since it is seen as stale and has been sent at least
 	// once. Once the message is removed, the peerHandler should be torn
 	// down as there are no longer any pending messages within the store.
-	err := lntest.WaitNoError(func() error {
+	err := wait.NoError(func() error {
 		msgs, err := reliableSender.cfg.MessageStore.MessagesForPeer(
 			peerPubKey,
 		)

discovery/sync_manager_test.go

@@ -9,7 +9,7 @@ import (
 	"time"
 
 	"github.com/davecgh/go-spew/spew"
-	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/ticker"
 )
@@ -504,7 +504,7 @@ func assertSyncerStatus(t *testing.T, s *GossipSyncer, syncState syncerState,
 
 	// We'll check the status of our syncer within a WaitPredicate as some
 	// sync transitions might cause this to be racy.
-	err := lntest.WaitNoError(func() error {
+	err := wait.NoError(func() error {
 		state := s.syncState()
 		if s.syncState() != syncState {
 			return fmt.Errorf("expected syncState %v for peer "+
@@ -545,7 +545,7 @@ func assertTransitionToChansSynced(t *testing.T, s *GossipSyncer, peer *mockPeer
 		t.Fatal("expected to receive FilterKnownChanIDs request")
 	}
 
-	err := lntest.WaitNoError(func() error {
+	err := wait.NoError(func() error {
 		state := syncerState(atomic.LoadUint32(&s.state))
 		if state != chansSynced {
 			return fmt.Errorf("expected syncerState %v, got %v",

lntest/harness.go

@@ -22,6 +22,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
 	"github.com/lightningnetwork/lnd/lnrpc"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
@@ -493,7 +494,7 @@ func (n *NetworkHarness) EnsureConnected(ctx context.Context, a, b *HarnessNode)
 		return false
 	}
 
-	err := WaitPredicate(func() bool {
+	err := wait.Predicate(func() bool {
 		return findSelfInPeerList(a, b) && findSelfInPeerList(b, a)
 	}, time.Second*15)
 	if err != nil {
@@ -526,7 +527,7 @@ func (n *NetworkHarness) ConnectNodes(ctx context.Context, a, b *HarnessNode) er
 		return err
 	}
 
-	err = WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		// If node B is seen in the ListPeers response from node A,
 		// then we can exit early as the connection has been fully
 		// established.
@@ -1068,12 +1069,12 @@ func (n *NetworkHarness) CloseChannel(ctx context.Context,
 
 		// Before proceeding, we'll ensure that the channel is active
 		// for both nodes.
-		err = WaitPredicate(activeChanPredicate(lnNode), timeout)
+		err = wait.Predicate(activeChanPredicate(lnNode), timeout)
 		if err != nil {
 			return nil, nil, fmt.Errorf("channel of closing " +
 				"node not active in time")
 		}
-		err = WaitPredicate(activeChanPredicate(receivingNode), timeout)
+		err = wait.Predicate(activeChanPredicate(receivingNode), timeout)
 		if err != nil {
 			return nil, nil, fmt.Errorf("channel of receiving " +
 				"node not active in time")
@@ -1194,85 +1195,13 @@ func (n *NetworkHarness) AssertChannelExists(ctx context.Context,
 		return false
 	}
 
-	if err := WaitPredicate(pred, time.Second*15); err != nil {
+	if err := wait.Predicate(pred, time.Second*15); err != nil {
 		return fmt.Errorf("channel not found: %v", predErr)
 	}
 
 	return nil
 }
 
-// WaitPredicate is a helper test function that will wait for a timeout period
-// of time until the passed predicate returns true. This function is helpful as
-// timing doesn't always line up well when running integration tests with
-// several running lnd nodes. This function gives callers a way to assert that
-// some property is upheld within a particular time frame.
-func WaitPredicate(pred func() bool, timeout time.Duration) error {
-	const pollInterval = 20 * time.Millisecond
-
-	exitTimer := time.After(timeout)
-	for {
-		<-time.After(pollInterval)
-
-		select {
-		case <-exitTimer:
-			return fmt.Errorf("predicate not satisfied after time out")
-		default:
-		}
-
-		if pred() {
-			return nil
-		}
-	}
-}
-
-// WaitNoError is a wrapper around WaitPredicate that waits for the passed
-// method f to execute without error, and returns the last error encountered if
-// this doesn't happen within the timeout.
-func WaitNoError(f func() error, timeout time.Duration) error {
-	var predErr error
-	pred := func() bool {
-		if err := f(); err != nil {
-			predErr = err
-			return false
-		}
-		return true
-	}
-
-	// If f() doesn't succeed within the timeout, return the last
-	// encountered error.
-	if err := WaitPredicate(pred, timeout); err != nil {
-		return predErr
-	}
-
-	return nil
-}
-
-// WaitInvariant is a helper test function that will wait for a timeout period
-// of time, verifying that a statement remains true for the entire duration.
-// This function is helpful as timing doesn't always line up well when running
-// integration tests with several running lnd nodes. This function gives callers
-// a way to assert that some property is maintained over a particular time
-// frame.
-func WaitInvariant(statement func() bool, timeout time.Duration) error {
-	const pollInterval = 20 * time.Millisecond
-
-	exitTimer := time.After(timeout)
-	for {
-		<-time.After(pollInterval)
-
-		// Fail if the invariant is broken while polling.
-		if !statement() {
-			return fmt.Errorf("invariant broken before time out")
-		}
-
-		select {
-		case <-exitTimer:
-			return nil
-		default:
-		}
-	}
-}
-
 // DumpLogs reads the current logs generated by the passed node, and returns
 // the logs as a single string. This function is useful for examining the logs
 // of a particular node in the case of a test failure.
@@ -1373,7 +1302,7 @@ func (n *NetworkHarness) sendCoins(ctx context.Context, amt btcutil.Amount,
 
 	// Now, wait for ListUnspent to show the unconfirmed transaction
 	// containing the correct pkscript.
-	err = WaitNoError(func() error {
+	err = wait.NoError(func() error {
 		// Since neutrino doesn't support unconfirmed outputs, skip
 		// this check.
 		if target.cfg.BackendCfg.Name() == "neutrino" {

lntest/itest/lnd_multi-hop_htlc_local_chain_claim_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/invoicesrpc"
 	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/lntypes"
 )
 
@@ -73,7 +74,7 @@ func testMultiHopHtlcLocalChainClaim(net *lntest.NetworkHarness, t *harnessTest)
 	// the created HTLC pending on all of them.
 	var predErr error
 	nodes := []*lntest.HarnessNode{net.Alice, net.Bob, carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertActiveHtlcs(nodes, payHash[:])
 		if predErr != nil {
 			return false
@@ -229,7 +230,7 @@ func testMultiHopHtlcLocalChainClaim(net *lntest.NetworkHarness, t *harnessTest)
 	// At this point, Bob should have broadcast his second layer success
 	// transaction, and should have sent it to the nursery for incubation.
 	pendingChansRequest := &lnrpc.PendingChannelsRequest{}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -321,7 +322,7 @@ func testMultiHopHtlcLocalChainClaim(net *lntest.NetworkHarness, t *harnessTest)
 	block = mineBlocks(t, net, 1, 1)[0]
 	assertTxInBlock(t, block, bobSweep)
 
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -357,7 +358,7 @@ func testMultiHopHtlcLocalChainClaim(net *lntest.NetworkHarness, t *harnessTest)
 	}
 
 	// Also Carol should have no channels left (open nor pending).
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := carol.PendingChannels(
 			ctxt, pendingChansRequest,

lntest/itest/lnd_multi-hop_htlc_receiver_chain_claim_test.go

@@ -14,6 +14,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/invoicesrpc"
 	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/lntypes"
 )
 
@@ -75,7 +76,7 @@ func testMultiHopReceiverChainClaim(net *lntest.NetworkHarness, t *harnessTest)
 	// the created HTLC pending on all of them.
 	var predErr error
 	nodes := []*lntest.HarnessNode{net.Alice, net.Bob, carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertActiveHtlcs(nodes, payHash[:])
 		if predErr != nil {
 			return false
@@ -230,7 +231,7 @@ func testMultiHopReceiverChainClaim(net *lntest.NetworkHarness, t *harnessTest)
 	// extracted the preimage from the chain, and sent it back to Alice,
 	// clearing the HTLC off-chain.
 	nodes = []*lntest.HarnessNode{net.Alice}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, 0)
 		if predErr != nil {
 			return false
@@ -259,7 +260,7 @@ func testMultiHopReceiverChainClaim(net *lntest.NetworkHarness, t *harnessTest)
 	if _, err := net.Miner.Node.Generate(1); err != nil {
 		t.Fatalf("unable to mine block: %v", err)
 	}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err = carol.PendingChannels(ctxt, pendingChansRequest)
 		if err != nil {

lntest/itest/lnd_multi-hop_htlc_remote_chain_claim_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/invoicesrpc"
 	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/lntypes"
 )
 
@@ -72,7 +73,7 @@ func testMultiHopHtlcRemoteChainClaim(net *lntest.NetworkHarness, t *harnessTest
 	// the created HTLC pending on all of them.
 	var predErr error
 	nodes := []*lntest.HarnessNode{net.Alice, net.Bob, carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertActiveHtlcs(nodes, payHash[:])
 		if predErr != nil {
 			return false
@@ -252,7 +253,7 @@ func testMultiHopHtlcRemoteChainClaim(net *lntest.NetworkHarness, t *harnessTest
 	// recognize that all contracts have been fully resolved, and show no
 	// pending close channels.
 	pendingChansRequest := &lnrpc.PendingChannelsRequest{}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -291,7 +292,7 @@ func testMultiHopHtlcRemoteChainClaim(net *lntest.NetworkHarness, t *harnessTest
 	assertTxInBlock(t, block, carolSweep)
 
 	pendingChansRequest = &lnrpc.PendingChannelsRequest{}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := carol.PendingChannels(
 			ctxt, pendingChansRequest,

lntest/itest/lnd_test.go

@@ -37,6 +37,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc/watchtowerrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/wtclientrpc"
 	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing"
@@ -366,7 +367,7 @@ func assertChannelClosed(ctx context.Context, t *harnessTest,
 	// Finally, the transaction should no longer be in the waiting close
 	// state as we've just mined a block that should include the closing
 	// transaction.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		pendingChansRequest := &lnrpc.PendingChannelsRequest{}
 		pendingChanResp, err := node.PendingChannels(
 			ctx, pendingChansRequest,
@@ -406,7 +407,7 @@ func waitForChannelPendingForceClose(ctx context.Context,
 	}
 
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		pendingChansRequest := &lnrpc.PendingChannelsRequest{}
 		pendingChanResp, err := node.PendingChannels(
 			ctx, pendingChansRequest,
@@ -480,7 +481,7 @@ func numOpenChannelsPending(ctxt context.Context, node *lntest.HarnessNode) (int
 func assertNumOpenChannelsPending(ctxt context.Context, t *harnessTest,
 	alice, bob *lntest.HarnessNode, expected int) {
 
-	err := lntest.WaitNoError(func() error {
+	err := wait.NoError(func() error {
 		aliceNumChans, err := numOpenChannelsPending(ctxt, alice)
 		if err != nil {
 			return fmt.Errorf("error fetching alice's node (%v) "+
@@ -643,7 +644,7 @@ func completePaymentRequests(ctx context.Context, client lnrpc.LightningClient,
 	// should still wait long enough for the server to receive and handle
 	// 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 {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctx, defaultTimeout)
 		newListResp, err := client.ListChannels(ctxt, req)
 		if err != nil {
@@ -783,7 +784,7 @@ func testOnchainFundRecovery(net *lntest.NetworkHarness, t *harnessTest) {
 			currBalance  int64
 			currNumUTXOs uint32
 		)
-		err = lntest.WaitPredicate(func() bool {
+		err = wait.Predicate(func() bool {
 			req := &lnrpc.WalletBalanceRequest{}
 			ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 			resp, err := node.WalletBalance(ctxt, req)
@@ -1741,7 +1742,7 @@ func testUpdateChannelPolicy(net *lntest.NetworkHarness, t *harnessTest) {
 func waitForNodeBlockHeight(ctx context.Context, node *lntest.HarnessNode,
 	height int32) error {
 	var predErr error
-	err := lntest.WaitPredicate(func() bool {
+	err := wait.Predicate(func() bool {
 		ctxt, _ := context.WithTimeout(ctx, 10*time.Second)
 		info, err := node.GetInfo(ctxt, &lnrpc.GetInfoRequest{})
 		if err != nil {
@@ -1769,7 +1770,7 @@ func assertMinerBlockHeightDelta(t *harnessTest,
 
 	// Ensure the chain lengths are what we expect.
 	var predErr error
-	err := lntest.WaitPredicate(func() bool {
+	err := wait.Predicate(func() bool {
 		_, tempMinerHeight, err := tempMiner.Node.GetBestBlock()
 		if err != nil {
 			predErr = fmt.Errorf("unable to get current "+
@@ -2003,7 +2004,7 @@ func testOpenChannelAfterReorg(net *lntest.NetworkHarness, t *harnessTest) {
 	}
 
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		chanGraph, err = net.Alice.DescribeGraph(ctxt, req)
 		if err != nil {
@@ -2132,7 +2133,7 @@ func testDisconnectingTargetPeer(net *lntest.NetworkHarness, t *harnessTest) {
 	// Disconnect Alice-peer from Bob-peer without getting error
 	// about existing channels.
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		if err := net.DisconnectNodes(ctxt, net.Alice, net.Bob); err != nil {
 			predErr = err
 			return false
@@ -2442,7 +2443,7 @@ func testChannelUnsettledBalance(net *lntest.NetworkHarness, t *harnessTest) {
 	// is equal to the amount of invoices * payAmt.
 	var unsettledErr error
 	nodes := []*lntest.HarnessNode{net.Alice, carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		// There should be a number of PendingHtlcs equal
 		// to the amount of Invoices sent.
 		unsettledErr = assertNumActiveHtlcs(nodes, numInvoices)
@@ -2715,7 +2716,7 @@ func testChannelForceClosure(net *lntest.NetworkHarness, t *harnessTest) {
 	// show that the HTLC has been locked in.
 	nodes := []*lntest.HarnessNode{net.Alice, carol}
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, numInvoices)
 		if predErr != nil {
 			return false
@@ -2818,7 +2819,7 @@ func testChannelForceClosure(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Now that the commitment has been confirmed, the channel should be
 	// marked as force closed.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Alice.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -2902,7 +2903,7 @@ func testChannelForceClosure(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Alice should see the channel in her set of pending force closed
 	// channels with her funds still in limbo.
-	err = lntest.WaitNoError(func() error {
+	err = wait.NoError(func() error {
 		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Alice.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -3006,7 +3007,7 @@ func testChannelForceClosure(net *lntest.NetworkHarness, t *harnessTest) {
 		t.Fatalf("unable to get best block height")
 	}
 
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		// Now that the commit output has been fully swept, check to see
 		// that the channel remains open for the pending htlc outputs.
 		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
@@ -3079,7 +3080,7 @@ func testChannelForceClosure(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Alice should now see the channel in her set of pending force closed
 	// channels with one pending HTLC.
-	err = lntest.WaitNoError(func() error {
+	err = wait.NoError(func() error {
 		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Alice.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -3207,7 +3208,7 @@ func testChannelForceClosure(net *lntest.NetworkHarness, t *harnessTest) {
 	// Now that the channel has been fully swept, it should no longer show
 	// incubated, check to see that Alice's node still reports the channel
 	// as pending force closed.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err = net.Alice.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -3308,7 +3309,7 @@ func testChannelForceClosure(net *lntest.NetworkHarness, t *harnessTest) {
 	// Now that the channel has been fully swept, it should no longer show
 	// incubated, check to see that Alice's node still reports the channel
 	// as pending force closed.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Alice.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -3357,7 +3358,7 @@ func testChannelForceClosure(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Now that the channel has been fully swept, it should no longer show
 	// up within the pending channels RPC.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Alice.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -4798,7 +4799,7 @@ func testUnannouncedChannels(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Give the network a chance to learn that auth proof is confirmed.
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		// The channel should now be announced. Check that Alice has 1
 		// announced edge.
 		req.IncludeUnannounced = false
@@ -5126,7 +5127,7 @@ func testPrivateChannels(net *lntest.NetworkHarness, t *harnessTest) {
 	}
 
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		aliceChans := numChannels(net.Alice, true)
 		if aliceChans != 4 {
 			predErr = fmt.Errorf("expected Alice to know 4 edges, "+
@@ -5319,7 +5320,7 @@ func testInvoiceRoutingHints(net *lntest.NetworkHarness, t *harnessTest) {
 	// Alice and Bob should be the only channel used as a routing hint.
 	var predErr error
 	var decoded *lnrpc.PayReq
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		resp, err := net.Alice.AddInvoice(ctxt, invoice)
 		if err != nil {
@@ -6329,7 +6330,7 @@ func testFailingChannel(net *lntest.NetworkHarness, t *harnessTest) {
 	// Since Alice detects that Carol is trying to trick her by providing a
 	// fake preimage, she should fail and force close the channel.
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		pendingChansRequest := &lnrpc.PendingChannelsRequest{}
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Alice.PendingChannels(ctxt,
@@ -6359,7 +6360,7 @@ func testFailingChannel(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// The channel should now show up as force closed both for Alice and
 	// Carol.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		pendingChansRequest := &lnrpc.PendingChannelsRequest{}
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Alice.PendingChannels(ctxt,
@@ -6387,7 +6388,7 @@ func testFailingChannel(net *lntest.NetworkHarness, t *harnessTest) {
 		t.Fatalf("%v", predErr)
 	}
 
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		pendingChansRequest := &lnrpc.PendingChannelsRequest{}
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := carol.PendingChannels(ctxt,
@@ -6435,7 +6436,7 @@ func testFailingChannel(net *lntest.NetworkHarness, t *harnessTest) {
 	}
 
 	// No pending channels should be left.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		pendingChansRequest := &lnrpc.PendingChannelsRequest{}
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Alice.PendingChannels(ctxt,
@@ -6545,13 +6546,13 @@ func testGarbageCollectLinkNodes(net *lntest.NetworkHarness, t *harnessTest) {
 		t.Fatalf("unable to restart carol's node: %v", err)
 	}
 
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		return isConnected(net.Bob.PubKeyStr)
 	}, 15*time.Second)
 	if err != nil {
 		t.Fatalf("alice did not reconnect to bob")
 	}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		return isConnected(carol.PubKeyStr)
 	}, 15*time.Second)
 	if err != nil {
@@ -6564,19 +6565,19 @@ func testGarbageCollectLinkNodes(net *lntest.NetworkHarness, t *harnessTest) {
 		t.Fatalf("unable to restart alice's node: %v", err)
 	}
 
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		return isConnected(net.Bob.PubKeyStr)
 	}, 15*time.Second)
 	if err != nil {
 		t.Fatalf("alice did not reconnect to bob")
 	}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		return isConnected(carol.PubKeyStr)
 	}, 15*time.Second)
 	if err != nil {
 		t.Fatalf("alice did not reconnect to carol")
 	}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		return isConnected(dave.PubKeyStr)
 	}, 15*time.Second)
 	if err != nil {
@@ -6604,7 +6605,7 @@ func testGarbageCollectLinkNodes(net *lntest.NetworkHarness, t *harnessTest) {
 			t.Fatalf("unable to restart %v's node: %v", node.Name(),
 				err)
 		}
-		err = lntest.WaitInvariant(func() bool {
+		err = wait.Invariant(func() bool {
 			return !isConnected(node.PubKeyStr)
 		}, 5*time.Second)
 		if err != nil {
@@ -6614,14 +6615,14 @@ func testGarbageCollectLinkNodes(net *lntest.NetworkHarness, t *harnessTest) {
 		if err := net.RestartNode(net.Alice, nil); err != nil {
 			t.Fatalf("unable to restart alice's node: %v", err)
 		}
-		err = lntest.WaitPredicate(func() bool {
+		err = wait.Predicate(func() bool {
 			return isConnected(dave.PubKeyStr)
 		}, 20*time.Second)
 		if err != nil {
 			t.Fatalf("alice didn't reconnect to Dave")
 		}
 
-		err = lntest.WaitInvariant(func() bool {
+		err = wait.Invariant(func() bool {
 			return !isConnected(node.PubKeyStr)
 		}, 5*time.Second)
 		if err != nil {
@@ -6656,7 +6657,7 @@ func testGarbageCollectLinkNodes(net *lntest.NetworkHarness, t *harnessTest) {
 	// fully cleaned up for both Carol and Alice.
 	var predErr error
 	pendingChansRequest := &lnrpc.PendingChannelsRequest{}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Alice.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -6801,7 +6802,7 @@ func testRevokedCloseRetribution(net *lntest.NetworkHarness, t *harnessTest) {
 	// satoshis each, Bob should now see his balance as being 30k satoshis.
 	var bobChan *lnrpc.Channel
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		bChan, err := getChanInfo(ctxt, net.Bob)
 		if err != nil {
@@ -6884,7 +6885,7 @@ func testRevokedCloseRetribution(net *lntest.NetworkHarness, t *harnessTest) {
 	// feel the wrath of Carol's retribution.
 	var closeUpdates lnrpc.Lightning_CloseChannelClient
 	force := true
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ := context.WithTimeout(ctxb, channelCloseTimeout)
 		closeUpdates, _, err = net.CloseChannel(ctxt, net.Bob, chanPoint, force)
 		if err != nil {
@@ -7129,7 +7130,7 @@ func testRevokedCloseRetributionZeroValueRemoteOutput(net *lntest.NetworkHarness
 		closeErr     error
 		force        bool = true
 	)
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ := context.WithTimeout(ctxb, channelCloseTimeout)
 		closeUpdates, closeTxId, closeErr = net.CloseChannel(
 			ctxt, carol, chanPoint, force,
@@ -7532,7 +7533,7 @@ func testRevokedCloseRetributionRemoteHodl(net *lntest.NetworkHarness,
 		return nil, errNotFound
 	}
 
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		txid, err := findJusticeTx()
 		if err != nil {
 			predErr = err
@@ -7552,7 +7553,7 @@ func testRevokedCloseRetributionRemoteHodl(net *lntest.NetworkHarness,
 		// as the last argument, indicating we don't care what's in the
 		// mempool.
 		mineBlocks(t, net, 1, 0)
-		err = lntest.WaitPredicate(func() bool {
+		err = wait.Predicate(func() bool {
 			txid, err := findJusticeTx()
 			if err != nil {
 				predErr = err
@@ -7938,7 +7939,7 @@ func testRevokedCloseRetributionAltruistWatchtower(net *lntest.NetworkHarness,
 	// Ensure that Willy doesn't get any funds, as he is acting as an
 	// altruist watchtower.
 	var predErr error
-	err = lntest.WaitInvariant(func() bool {
+	err = wait.Invariant(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		willyBalReq := &lnrpc.WalletBalanceRequest{}
 		willyBalResp, err := willy.WalletBalance(ctxt, willyBalReq)
@@ -7967,7 +7968,7 @@ func testRevokedCloseRetributionAltruistWatchtower(net *lntest.NetworkHarness,
 		t.Fatalf("unable to restart dave: %v", err)
 	}
 
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		daveBalReq := &lnrpc.ChannelBalanceRequest{}
 		daveBalResp, err := dave.ChannelBalance(ctxt, daveBalReq)
@@ -7990,7 +7991,7 @@ func testRevokedCloseRetributionAltruistWatchtower(net *lntest.NetworkHarness,
 
 	assertNumPendingChannels(t, dave, 0, 0)
 
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 		daveBalReq := &lnrpc.WalletBalanceRequest{}
 		daveBalResp, err := dave.WalletBalance(ctxt, daveBalReq)
@@ -8023,7 +8024,7 @@ func assertNumPendingChannels(t *harnessTest, node *lntest.HarnessNode,
 	ctxb := context.Background()
 
 	var predErr error
-	err := lntest.WaitPredicate(func() bool {
+	err := wait.Predicate(func() bool {
 		pendingChansRequest := &lnrpc.PendingChannelsRequest{}
 		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := node.PendingChannels(ctxt,
@@ -8256,7 +8257,7 @@ func testDataLossProtection(net *lntest.NetworkHarness, t *harnessTest) {
 		// as being 30k satoshis.
 		var nodeChan *lnrpc.Channel
 		var predErr error
-		err = lntest.WaitPredicate(func() bool {
+		err = wait.Predicate(func() bool {
 			ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 			bChan, err := getChanInfo(ctxt, node)
 			if err != nil {
@@ -8455,7 +8456,7 @@ func testDataLossProtection(net *lntest.NetworkHarness, t *harnessTest) {
 	mineBlocks(t, net, 1, 1)
 	assertNodeNumChannels(t, dave, 0)
 
-	err = lntest.WaitNoError(func() error {
+	err = wait.NoError(func() error {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		daveBalResp, err := dave.WalletBalance(ctxt, balReq)
 		if err != nil {
@@ -8507,7 +8508,7 @@ func assertNodeNumChannels(t *harnessTest, node *lntest.HarnessNode,
 		return true
 	}
 
-	if err := lntest.WaitPredicate(pred, time.Second*15); err != nil {
+	if err := wait.Predicate(pred, time.Second*15); err != nil {
 		t.Fatalf("node has incorrect number of channels: %v", predErr)
 	}
 }
@@ -9591,7 +9592,7 @@ func testAsyncPayments(net *lntest.NetworkHarness, t *harnessTest) {
 	// Wait for the revocation to be received so alice no longer has pending
 	// htlcs listed and has correct balances. This is needed due to the fact
 	// that we now pipeline the settles.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		aliceChan, err := getChanInfo(ctxt, net.Alice)
 		if err != nil {
@@ -10124,7 +10125,7 @@ func testMultiHopHtlcLocalTimeout(net *lntest.NetworkHarness, t *harnessTest) {
 	// proper parameters.
 	var predErr error
 	nodes := []*lntest.HarnessNode{net.Alice, net.Bob, carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertActiveHtlcs(nodes, dustPayHash, payHash)
 		if predErr != nil {
 			return false
@@ -10170,7 +10171,7 @@ func testMultiHopHtlcLocalTimeout(net *lntest.NetworkHarness, t *harnessTest) {
 	// that we sent earlier. This means Alice should now only have a single
 	// HTLC on her channel.
 	nodes = []*lntest.HarnessNode{net.Alice}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertActiveHtlcs(nodes, payHash)
 		if predErr != nil {
 			return false
@@ -10236,7 +10237,7 @@ func testMultiHopHtlcLocalTimeout(net *lntest.NetworkHarness, t *harnessTest) {
 	// Therefore, at this point, there should be no active HTLC's on the
 	// commitment transaction from Alice -> Bob.
 	nodes = []*lntest.HarnessNode{net.Alice}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, 0)
 		if predErr != nil {
 			return false
@@ -10267,7 +10268,7 @@ func testMultiHopHtlcLocalTimeout(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Once this transaction has been confirmed, Bob should detect that he
 	// no longer has any pending channels.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err = net.Bob.PendingChannels(ctxt, pendingChansRequest)
 		if err != nil {
@@ -10343,7 +10344,7 @@ func testMultiHopLocalForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 	// have the it locked in.
 	var predErr error
 	nodes := []*lntest.HarnessNode{net.Alice, net.Bob, carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertActiveHtlcs(nodes, payHash)
 		if predErr != nil {
 			return false
@@ -10364,7 +10365,7 @@ func testMultiHopLocalForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 	// At this point, Bob should have a pending force close channel as he
 	// just went to chain.
 	pendingChansRequest := &lnrpc.PendingChannelsRequest{}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(ctxt,
 			pendingChansRequest)
@@ -10413,7 +10414,7 @@ func testMultiHopLocalForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 
 	// Bob's pending channel report should show that he has a single HTLC
 	// that's now in stage one.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -10463,7 +10464,7 @@ func testMultiHopLocalForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 	// With the second layer timeout transaction confirmed, Bob should have
 	// cancelled backwards the HTLC that carol sent.
 	nodes = []*lntest.HarnessNode{net.Alice}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, 0)
 		if predErr != nil {
 			return false
@@ -10476,7 +10477,7 @@ func testMultiHopLocalForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 
 	// Additionally, Bob should now show that HTLC as being advanced to the
 	// second stage.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -10530,7 +10531,7 @@ func testMultiHopLocalForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 
 	// At this point, Bob should no longer show any channels as pending
 	// close.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -10607,7 +10608,7 @@ func testMultiHopRemoteForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 	// show that the HTLC has been locked in.
 	var predErr error
 	nodes := []*lntest.HarnessNode{net.Alice, net.Bob, carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertActiveHtlcs(nodes, payHash)
 		if predErr != nil {
 			return false
@@ -10628,7 +10629,7 @@ func testMultiHopRemoteForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 	// At this point, Bob should have a pending force close channel as
 	// Carol has gone directly to chain.
 	pendingChansRequest := &lnrpc.PendingChannelsRequest{}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -10668,7 +10669,7 @@ func testMultiHopRemoteForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 	// If we check Bob's pending channel report, it should show that he has
 	// a single HTLC that's now in the second stage, as skip the initial
 	// first stage since this is a direct HTLC.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -10734,7 +10735,7 @@ func testMultiHopRemoteForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 	// cancel back that HTLC. As a result, Alice should not know of any
 	// active HTLC's.
 	nodes = []*lntest.HarnessNode{net.Alice}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, 0)
 		if predErr != nil {
 			return false
@@ -10748,7 +10749,7 @@ func testMultiHopRemoteForceCloseOnChainHtlcTimeout(net *lntest.NetworkHarness,
 	// Now we'll check Bob's pending channel report. Since this was Carol's
 	// commitment, he doesn't have to wait for any CSV delays. As a result,
 	// he should show no additional pending transactions.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		pendingChanResp, err := net.Bob.PendingChannels(
 			ctxt, pendingChansRequest,
@@ -10952,7 +10953,7 @@ func testSwitchCircuitPersistence(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Wait until all nodes in the network have 5 outstanding htlcs.
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, numPayments)
 		if predErr != nil {
 			return false
@@ -10990,7 +10991,7 @@ func testSwitchCircuitPersistence(net *lntest.NetworkHarness, t *harnessTest) {
 	}
 
 	// Ensure all nodes in the network still have 5 outstanding htlcs.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, numPayments)
 		if predErr != nil {
 			return false
@@ -11017,7 +11018,7 @@ func testSwitchCircuitPersistence(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// After the payments settle, there should be no active htlcs on any of
 	// the nodes in the network.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, 0)
 		if predErr != nil {
 			return false
@@ -11275,7 +11276,7 @@ func testSwitchOfflineDelivery(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Wait for all of the payments to reach Carol.
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, numPayments)
 		if predErr != nil {
 			return false
@@ -11301,7 +11302,7 @@ func testSwitchOfflineDelivery(net *lntest.NetworkHarness, t *harnessTest) {
 	// Wait to ensure that the payment remain are not failed back after
 	// reconnecting. All node should report the number payments initiated
 	// for the duration of the interval.
-	err = lntest.WaitInvariant(func() bool {
+	err = wait.Invariant(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, numPayments)
 		if predErr != nil {
 			return false
@@ -11328,7 +11329,7 @@ func testSwitchOfflineDelivery(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Wait for Carol to report no outstanding htlcs.
 	carolNode := []*lntest.HarnessNode{carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(carolNode, 0)
 		if predErr != nil {
 			return false
@@ -11347,7 +11348,7 @@ func testSwitchOfflineDelivery(net *lntest.NetworkHarness, t *harnessTest) {
 	}
 
 	// Wait until all outstanding htlcs in the network have been settled.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, 0)
 		if predErr != nil {
 			return false
@@ -11603,7 +11604,7 @@ func testSwitchOfflineDeliveryPersistence(net *lntest.NetworkHarness, t *harness
 	}
 
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, numPayments)
 		if predErr != nil {
 			return false
@@ -11640,7 +11641,7 @@ func testSwitchOfflineDeliveryPersistence(net *lntest.NetworkHarness, t *harness
 	// Wait for Carol to report no outstanding htlcs, and also for Dav to
 	// receive all the settles from Carol.
 	carolNode := []*lntest.HarnessNode{carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(carolNode, 0)
 		if predErr != nil {
 			return false
@@ -11675,7 +11676,7 @@ func testSwitchOfflineDeliveryPersistence(net *lntest.NetworkHarness, t *harness
 
 	// After reconnection succeeds, the settles should be propagated all
 	// the way back to the sender. All nodes should report no active htlcs.
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, 0)
 		if predErr != nil {
 			return false
@@ -11938,7 +11939,7 @@ func testSwitchOfflineDeliveryOutgoingOffline(
 
 	// Wait for all payments to reach Carol.
 	var predErr error
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodes, numPayments)
 		if predErr != nil {
 			return false
@@ -11965,7 +11966,7 @@ func testSwitchOfflineDeliveryOutgoingOffline(
 
 	// Wait for Carol to report no outstanding htlcs.
 	carolNode := []*lntest.HarnessNode{carol}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(carolNode, 0)
 		if predErr != nil {
 			return false
@@ -12016,7 +12017,7 @@ func testSwitchOfflineDeliveryOutgoingOffline(
 	// Since Carol has been shutdown permanently, we will wait until all
 	// other nodes in the network report no active htlcs.
 	nodesMinusCarol := []*lntest.HarnessNode{net.Bob, net.Alice, dave}
-	err = lntest.WaitPredicate(func() bool {
+	err = wait.Predicate(func() bool {
 		predErr = assertNumActiveHtlcs(nodesMinusCarol, 0)
 		if predErr != nil {
 			return false
@@ -13110,7 +13111,7 @@ func testChannelBackupUpdates(net *lntest.NetworkHarness, t *harnessTest) {
 	// assertBackupFileState is a helper function that we'll use to compare
 	// the on disk back up file to our currentBackup pointer above.
 	assertBackupFileState := func() {
-		err := lntest.WaitNoError(func() error {
+		err := wait.NoError(func() error {
 			packedBackup, err := ioutil.ReadFile(backupFilePath)
 			if err != nil {
 				return fmt.Errorf("unable to read backup "+
@@ -13254,7 +13255,7 @@ func testExportChannelBackup(net *lntest.NetworkHarness, t *harnessTest) {
 	// Before we proceed, we'll make two utility methods we'll use below
 	// for our primary assertions.
 	assertNumSingleBackups := func(numSingles int) {
-		err := lntest.WaitNoError(func() error {
+		err := wait.NoError(func() error {
 			ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
 			req := &lnrpc.ChanBackupExportRequest{}
 			chanSnapshot, err := carol.ExportAllChannelBackups(
@@ -13896,7 +13897,7 @@ func testHoldInvoicePersistence(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// The payments should now show up in Alice's ListInvoices, with a zero
 	// preimage, indicating they are not yet settled.
-	err = lntest.WaitNoError(func() error {
+	err = wait.NoError(func() error {
 		req := &lnrpc.ListPaymentsRequest{
 			IncludeIncomplete: true,
 		}

lntest/itest/onchain.go

@@ -12,6 +12,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/walletrpc"
 	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/sweep"
 )
 
@@ -140,7 +141,7 @@ func testCPFP(net *lntest.NetworkHarness, t *harnessTest) {
 	mineBlocks(t, net, 1, 2)
 
 	// The input used to CPFP should no longer be pending.
-	err = lntest.WaitNoError(func() error {
+	err = wait.NoError(func() error {
 		req := &walletrpc.PendingSweepsRequest{}
 		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 		resp, err := net.Bob.WalletKitClient.PendingSweeps(ctxt, req)

lntest/node.go

@@ -27,6 +27,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc/walletrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/watchtowerrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/wtclientrpc"
+	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/lightningnetwork/lnd/macaroons"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
@@ -468,7 +469,7 @@ func (hn *HarnessNode) initClientWhenReady() error {
 		conn    *grpc.ClientConn
 		connErr error
 	)
-	if err := WaitNoError(func() error {
+	if err := wait.NoError(func() error {
 		conn, connErr = hn.ConnectRPC(true)
 		return connErr
 	}, 5*time.Second); err != nil {
@@ -543,7 +544,7 @@ func (hn *HarnessNode) initLightningClient(conn *grpc.ClientConn) error {
 	// until then, we'll create a dummy subscription to ensure we can do so
 	// successfully before proceeding. We use a dummy subscription in order
 	// to not consume an update from the real one.
-	err = WaitNoError(func() error {
+	err = wait.NoError(func() error {
 		req := &lnrpc.GraphTopologySubscription{}
 		ctx, cancelFunc := context.WithCancel(context.Background())
 		topologyClient, err := hn.SubscribeChannelGraph(ctx, req)
@@ -1064,7 +1065,7 @@ func (hn *HarnessNode) WaitForBalance(expectedBalance btcutil.Amount, confirmed
 		return btcutil.Amount(balance.UnconfirmedBalance) == expectedBalance
 	}
 
-	err := WaitPredicate(doesBalanceMatch, 30*time.Second)
+	err := wait.Predicate(doesBalanceMatch, 30*time.Second)
 	if err != nil {
 		return fmt.Errorf("balances not synced after deadline: "+
 			"expected %v, only have %v", expectedBalance, lastBalance)

lntest/wait/wait.go

@@ -0,0 +1,78 @@
+package wait
+
+import (
+	"fmt"
+	"time"
+)
+
+// Predicate is a helper test function that will wait for a timeout period of
+// time until the passed predicate returns true. This function is helpful as
+// timing doesn't always line up well when running integration tests with
+// several running lnd nodes. This function gives callers a way to assert that
+// some property is upheld within a particular time frame.
+func Predicate(pred func() bool, timeout time.Duration) error {
+	const pollInterval = 20 * time.Millisecond
+
+	exitTimer := time.After(timeout)
+	for {
+		<-time.After(pollInterval)
+
+		select {
+		case <-exitTimer:
+			return fmt.Errorf("predicate not satisfied after time out")
+		default:
+		}
+
+		if pred() {
+			return nil
+		}
+	}
+}
+
+// NoError is a wrapper around Predicate that waits for the passed method f to
+// execute without error, and returns the last error encountered if this doesn't
+// happen within the timeout.
+func NoError(f func() error, timeout time.Duration) error {
+	var predErr error
+	pred := func() bool {
+		if err := f(); err != nil {
+			predErr = err
+			return false
+		}
+		return true
+	}
+
+	// If f() doesn't succeed within the timeout, return the last
+	// encountered error.
+	if err := Predicate(pred, timeout); err != nil {
+		return predErr
+	}
+
+	return nil
+}
+
+// Invariant is a helper test function that will wait for a timeout period of
+// time, verifying that a statement remains true for the entire duration.  This
+// function is helpful as timing doesn't always line up well when running
+// integration tests with several running lnd nodes. This function gives callers
+// a way to assert that some property is maintained over a particular time
+// frame.
+func Invariant(statement func() bool, timeout time.Duration) error {
+	const pollInterval = 20 * time.Millisecond
+
+	exitTimer := time.After(timeout)
+	for {
+		<-time.After(pollInterval)
+
+		// Fail if the invariant is broken while polling.
+		if !statement() {
+			return fmt.Errorf("invariant broken before time out")
+		}
+
+		select {
+		case <-exitTimer:
+			return nil
+		default:
+		}
+	}
+}