test: refactor lockup_drain add helpers drain and force_feerates

contrib/pyln-testing/pyln/testing/utils.py

@@ -1,4 +1,5 @@
 from bitcoin.rpc import RawProxy as BitcoinProxy
+from pyln.client import RpcError
 from pyln.testing.btcproxy import BitcoinRpcProxy
 from collections import OrderedDict
 from decimal import Decimal
@@ -811,6 +812,7 @@ class LightningNode(object):
                     if 'htlcs' in channel:
                         wait_for(lambda: len(self.rpc.listpeers()['peers'][p]['channels'][c]['htlcs']) == 0)
 
+    # This sends money to a directly connected peer
     def pay(self, dst, amt, label=None):
         if not label:
             label = ''.join(random.choice(string.ascii_letters + string.digits) for _ in range(20))
@@ -839,6 +841,18 @@ class LightningNode(object):
         result = self.rpc.waitsendpay(rhash)
         assert(result.get('status') == 'complete')
 
+    # This helper sends all money to a peer until even 1 msat can't get through.
+    def drain(self, peer):
+        total = 0
+        msat = 16**9
+        while msat != 0:
+            try:
+                self.pay(peer, msat)
+                total += msat
+            except RpcError:
+                msat //= 2
+        return total
+
     # Note: this feeds through the smoother in update_feerate, so changing
     # it on a running daemon may not give expected result!
     def set_feerates(self, feerates, wait_for_effect=True):
@@ -868,6 +882,15 @@ class LightningNode(object):
         if wait_for_effect:
             wait_for(lambda: self.daemon.rpcproxy.mock_counts['estimatesmartfee'] >= 3)
 
+    # force new feerates by restarting and thus skipping slow smoothed process
+    # Note: testnode must be created with: opts={'may_reconnect': True}
+    def force_feerates(self, rate):
+        assert(self.may_reconnect)
+        self.set_feerates([rate] * 3, False)
+        self.restart()
+        self.daemon.wait_for_log('peer_out WIRE_UPDATE_FEE')
+        assert(self.rpc.feerates('perkw')['perkw']['normal'] == rate)
+
     def wait_for_onchaind_broadcast(self, name, resolve=None):
         """Wait for onchaind to drop tx name to resolve (if any)"""
         if resolve: