added a simple test

tests/test_renepay.py

@@ -360,3 +360,36 @@ def test_hardmpp(node_factory):
     invoice = only_one(l6.rpc.listinvoices('inv2')['invoices'])
     assert isinstance(invoice['amount_received_msat'], Millisatoshi)
     assert invoice['amount_received_msat'] >= Millisatoshi('1800000sat')
+
+def test_fee_allocation(node_factory):
+    '''
+    Topology:
+    1----2
+    |    |
+    3----4
+    This a payment that fails if fee is not allocated as part of the flow
+    constraints.
+    '''
+    # High fees at 4%
+    opts = [
+        {'disable-mpp': None, 'fee-base': 1000 , 'fee-per-satoshi': 30000},
+    ]
+    l1, l2, l3, l4 = node_factory.get_nodes(4, opts=opts * 4)
+    start_channels([(l1, l2, 1000000), (l2, l4, 2000000),
+                    (l1, l3, 1000000), (l3, l4, 2000000)])
+
+    inv = l4.rpc.invoice("1500000sat", "inv", 'description')
+
+    out = subprocess.check_output(['cli/lightning-cli',
+                                   '--network={}'.format(TEST_NETWORK),
+                                   '--lightning-dir={}'
+                                   .format(l1.daemon.lightning_dir),
+                                   '-k',
+                                   'renepay',
+                                   'invstring={}'.format(inv['bolt11']),
+                                   'maxfee=75000sat',
+                                   ]).decode('utf-8')
+    l1.wait_for_htlcs()
+    invoice = only_one(l4.rpc.listinvoices('inv')['invoices'])
+    assert isinstance(invoice['amount_received_msat'], Millisatoshi)
+    assert invoice['amount_received_msat'] >= Millisatoshi('1500000sat')