lntest+itest: extend CloseChannelAssertPending

In this commit, we extend `CloseChannelAssertPending` with new args that
returns the raw close status update (as we have more things we'd like to
assert), and also allows us to pass in a custom fee rate.

itest/lnd_revocation_test.go

@@ -109,7 +109,11 @@ func breachRetributionTestCase(ht *lntest.HarnessTest,
 	// broadcasting his current channel state. This is actually the
 	// commitment transaction of a prior *revoked* state, so he'll soon
 	// feel the wrath of Carol's retribution.
-	_, breachTXID := ht.CloseChannelAssertPending(bob, chanPoint, true)
+	_, breachCloseUpd := ht.CloseChannelAssertPending(bob, chanPoint, true)
+	closeUpd := breachCloseUpd.GetClosePending()
+	require.NotNil(ht, closeUpd)
+	breachTXID, err := chainhash.NewHash(closeUpd.Txid)
+	require.NoError(ht, err)
 
 	// Here, Carol sees Bob's breach transaction in the mempool, but is
 	// waiting for it to confirm before continuing her retribution. We
@@ -543,9 +547,13 @@ func revokedCloseRetributionRemoteHodlCase(ht *lntest.HarnessTest,
 	// broadcasting her current channel state. This is actually the
 	// commitment transaction of a prior *revoked* state, so she'll soon
 	// feel the wrath of Dave's retribution.
-	closeUpdates, closeTxID := ht.CloseChannelAssertPending(
+	closeUpdates, closeUpd := ht.CloseChannelAssertPending(
 		carol, chanPoint, true,
 	)
+	pendingCloseUpd := closeUpd.GetClosePending()
+	require.NotNil(ht, pendingCloseUpd)
+	closeTxID, err := chainhash.NewHash(pendingCloseUpd.Txid)
+	require.NoError(ht, err)
 
 	// Generate a single block to mine the breach transaction.
 	block := ht.MineBlocksAndAssertNumTxes(1, 1)[0]
@@ -593,7 +601,7 @@ func revokedCloseRetributionRemoteHodlCase(ht *lntest.HarnessTest,
 		return nil, errNotFound
 	}
 
-	err := wait.NoError(func() error {
+	err = wait.NoError(func() error {
 		txid, err := findJusticeTx()
 		if err != nil {
 			return err

lntest/harness.go

@@ -1255,14 +1255,40 @@ func (h *HarnessTest) OpenChannelAssertErr(srcNode, destNode *node.HarnessNode,
 		"error returned, want %v, got %v", expectedErr, err)
 }
 
+// closeChannelOpts holds the options for closing a channel.
+type closeChannelOpts struct {
+	feeRate fn.Option[chainfee.SatPerVByte]
+}
+
+// CloseChanOpt is a functional option to modify the way we close a channel.
+type CloseChanOpt func(*closeChannelOpts)
+
+// WithCoopCloseFeeRate is a functional option to set the fee rate for a coop
+// close attempt.
+func WithCoopCloseFeeRate(rate chainfee.SatPerVByte) CloseChanOpt {
+	return func(o *closeChannelOpts) {
+		o.feeRate = fn.Some(rate)
+	}
+}
+
+// defaultCloseOpts returns the set of default close options.
+func defaultCloseOpts() *closeChannelOpts {
+	return &closeChannelOpts{}
+}
+
 // CloseChannelAssertPending attempts to close the channel indicated by the
 // passed channel point, initiated by the passed node. Once the CloseChannel
 // rpc is called, it will consume one event and assert it's a close pending
 // event. In addition, it will check that the closing tx can be found in the
 // mempool.
 func (h *HarnessTest) CloseChannelAssertPending(hn *node.HarnessNode,
-	cp *lnrpc.ChannelPoint,
-	force bool) (rpc.CloseChanClient, *chainhash.Hash) {
+	cp *lnrpc.ChannelPoint, force bool,
+	opts ...CloseChanOpt) (rpc.CloseChanClient, *lnrpc.CloseStatusUpdate) {
+
+	closeOpts := defaultCloseOpts()
+	for _, optFunc := range opts {
+		optFunc(closeOpts)
+	}
 
 	// Calls the rpc to close the channel.
 	closeReq := &lnrpc.CloseChannelRequest{
@@ -1271,10 +1297,9 @@ func (h *HarnessTest) CloseChannelAssertPending(hn *node.HarnessNode,
 		NoWait:       true,
 	}
 
-	// For coop close, we use a default confg target of 6.
-	if !force {
-		closeReq.TargetConf = 6
-	}
+	closeOpts.feeRate.WhenSome(func(feeRate chainfee.SatPerVByte) {
+		closeReq.SatPerVbyte = uint64(feeRate)
+	})
 
 	var (
 		stream rpc.CloseChanClient
@@ -1307,7 +1332,7 @@ func (h *HarnessTest) CloseChannelAssertPending(hn *node.HarnessNode,
 	// Assert the closing tx is in the mempool.
 	h.miner.AssertTxInMempool(closeTxid)
 
-	return stream, closeTxid
+	return stream, event
 }
 
 // CloseChannel attempts to coop close a non-anchored channel identified by the