test: test open channel with unknown fees

tests/test_opening.py

@@ -17,6 +17,34 @@ def find_next_feerate(node, peer):
     chan = only_one(node.rpc.listpeerchannels(peer.info['id'])['channels'])
     return chan['next_feerate']
 
+@pytest.mark.openchannel('v1')
+@pytest.mark.xfail(strict=True)
+@unittest.skipIf(TEST_NETWORK != 'regtest', "requires regtest")
+def test_opening_with_unknown_feerates(node_factory, bitcoind):
+    """
+    Test openchannel when feerates are unknown (like on signet/testnet with empty mempool).
+    """
+    opts = {
+        'feerates': None, 
+        'dev-no-fake-fees': True,
+    }
+
+    l1, l2 = node_factory.get_nodes(2, opts=[opts, {}])
+
+    # Verify fee estimation is failing only on l1
+    l1.daemon.wait_for_log('Unable to estimate any fees')
+
+    # Connect nodes and fund l1
+    l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
+    l1.fundwallet(10000000)
+
+    # Opening should fail due to unknown feerates
+    with pytest.raises(RpcError, match=r"Cannot estimate fees"):
+        l1.rpc.fundchannel(l2.info['id'], 1000000, minconf=0)
+
+    # Opening should work fine since fees are specified manually
+    l1.rpc.fundchannel(l2.info['id'], 1000000, feerate='1perkw', minconf=0)
+
 
 @unittest.skipIf(TEST_NETWORK != 'regtest', 'elementsd doesnt yet support PSBT features we need')
 @pytest.mark.openchannel('v2')