lnwallet/btcwallet: add compile time check for BlockChainIO interface

sweep/test_utils.go

@@ -10,6 +10,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/lnwallet"
 )
 
 var (
@@ -237,6 +238,8 @@ func (m *MockNotifier) RegisterSpendNtfn(outpoint *wire.OutPoint,
 
 type mockChainIO struct{}
 
+var _ lnwallet.BlockChainIO = (*mockChainIO)(nil)
+
 func (m *mockChainIO) GetBestBlock() (*chainhash.Hash, int32, error) {
 	return nil, mockChainIOHeight, nil
 }