lntest+itest: add method AssertNumTxsInMempool and AssertTxInBlock

in harness

Prepare to make `HarnessTest.Miner` a private instance to sync height.

lntest/harness.go

@@ -1193,7 +1193,7 @@ func (h *HarnessTest) openChannel(alice, bob *node.HarnessNode,
 
 	// Check that the funding tx is found in the first block.
 	fundingTxID := h.GetChanPointFundingTxid(fundingChanPoint)
-	h.Miner.AssertTxInBlock(block, fundingTxID)
+	h.AssertTxInBlock(block, fundingTxID)
 
 	// Check that both alice and bob have seen the channel from their
 	// network topology.

lntest/harness_assertion.go

@@ -656,7 +656,7 @@ func (h *HarnessTest) AssertStreamChannelCoopClosed(hn *node.HarnessNode,
 	// Consume one close event and assert the closing txid can be found in
 	// the block.
 	closingTxid := h.WaitForChannelCloseEvent(stream)
-	h.Miner.AssertTxInBlock(block, closingTxid)
+	h.AssertTxInBlock(block, closingTxid)
 
 	// We should see zero waiting close channels now.
 	h.AssertNumWaitingClose(hn, 0)
@@ -700,7 +700,7 @@ func (h *HarnessTest) AssertStreamChannelForceClosed(hn *node.HarnessNode,
 	// Consume one close event and assert the closing txid can be found in
 	// the block.
 	closingTxid := h.WaitForChannelCloseEvent(stream)
-	h.Miner.AssertTxInBlock(block, closingTxid)
+	h.AssertTxInBlock(block, closingTxid)
 
 	// We should see zero waiting close channels and 1 pending force close
 	// channels now.
@@ -2564,7 +2564,7 @@ func (h *HarnessTest) AssertClosingTxInMempool(cp *lnrpc.ChannelPoint,
 	}
 
 	// Wait for the expected txes to be found in the mempool.
-	h.Miner.AssertNumTxsInMempool(expectedTxes)
+	h.AssertNumTxsInMempool(expectedTxes)
 
 	// Get the closing tx from the mempool.
 	op := h.OutPointFromChannelPoint(cp)
@@ -2578,7 +2578,7 @@ func (h *HarnessTest) AssertClosingTxInMempool(cp *lnrpc.ChannelPoint,
 // will assert the anchor sweep tx is also in the mempool.
 func (h *HarnessTest) MineClosingTx(cp *lnrpc.ChannelPoint) *wire.MsgTx {
 	// Wait for the expected txes to be found in the mempool.
-	h.Miner.AssertNumTxsInMempool(1)
+	h.AssertNumTxsInMempool(1)
 
 	// Get the closing tx from the mempool.
 	op := h.OutPointFromChannelPoint(cp)

lntest/harness_miner.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/btcsuite/btcd/blockchain"
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/lntest/node"
 	"github.com/lightningnetwork/lnd/lntest/wait"
@@ -177,3 +178,17 @@ func (h *HarnessTest) mineTillForceCloseResolved(hn *node.HarnessNode) {
 
 	require.NoErrorf(h, err, "assert force close resolved timeout")
 }
+
+// AssertNumTxsInMempool polls until finding the desired number of transactions
+// in the provided miner's mempool. It will asserrt if this number is not met
+// after the given timeout.
+func (h *HarnessTest) AssertNumTxsInMempool(n int) []*chainhash.Hash {
+	return h.Miner.AssertNumTxsInMempool(n)
+}
+
+// AssertTxInBlock asserts that a given txid can be found in the passed block.
+func (h *HarnessTest) AssertTxInBlock(block *wire.MsgBlock,
+	txid *chainhash.Hash) {
+
+	h.Miner.AssertTxInBlock(block, txid)
+}