pytest: Stabilize and parameterize closing_specified_destination

This test was doing a few contortions, so I disentangled it a bit and
parametrized it

contrib/pyln-testing/pyln/testing/fixtures.py

@@ -305,6 +305,7 @@ def chainparams():
     """Return the chainparams for the TEST_NETWORK.
 
      - chain_hash is in network byte order, not the RPC return order.
+     - example_addr doesn't belong to any node in the test (randomly generated)
 
     """
     chainparams = {
@@ -324,7 +325,7 @@ def chainparams():
             "name": "liquid-regtest",
             "p2sh_prefix": 'X',
             "elements": True,
-            "example_addr": "ert1qq8adjz4u6enf0cjey9j8yt0y490tact9fahkwf",
+            "example_addr": "ert1qjsesxflhs3632syhcz7llpfx20p5tr0kpllfve",
             "feeoutput": True,
             "chain_hash": "9f87eb580b9e5f11dc211e9fb66abb3699999044f8fe146801162393364286c6",
         }

tests/test_closing.py

@@ -298,7 +298,7 @@ def test_closing_negotiation_reconnect(node_factory, bitcoind):
 
 
 @unittest.skipIf(not DEVELOPER, "needs DEVELOPER=1")
-def test_closing_specified_destination(node_factory, bitcoind):
+def test_closing_specified_destination(node_factory, bitcoind, chainparams):
     l1, l2, l3, l4 = node_factory.get_nodes(4)
 
     l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
@@ -314,7 +314,7 @@ def test_closing_specified_destination(node_factory, bitcoind):
     l1.pay(l4, 100000000)
 
     bitcoind.generate_block(5)
-    addr = 'bcrt1qeyyk6sl5pr49ycpqyckvmttus5ttj25pd0zpvg'
+    addr = chainparams['example_addr']
     l1.rpc.close(chan12, None, addr)
     l1.rpc.call('close', {'id': chan13, 'destination': addr})
     l1.rpc.call('close', [chan14, None, addr])
@@ -327,38 +327,33 @@ def test_closing_specified_destination(node_factory, bitcoind):
     assert bitcoind.rpc.getmempoolinfo()['size'] == 3
 
     # Now grab the close transaction
-    closetxid = bitcoind.rpc.getrawmempool(False)
+    closetxs = {}
-    assert len(closetxid) == 3
+    for i, n in enumerate([l2, l3, l4]):
-
+        billboard = only_one(l1.rpc.listpeers(n.info['id'])['peers'][0]['channels'])['status'][0]
-    idindex = {}
+        m = re.search(r'CLOSINGD_SIGEXCHANGE.* tx:([a-f0-9]{64})', billboard)
-    for n in [l2, l3, l4]:
+        closetxs[n] = m.group(1)
-        billboard = only_one(l1.rpc.listpeers(n.info['id'])['peers'][0]['channels'])['status']
-        idindex[n] = [i for i in range(3) if billboard == [
-            'CLOSINGD_SIGEXCHANGE:We agreed on a closing fee of 5430 satoshi for tx:{}'.format(closetxid[i]),
-        ]][0]
-        assert idindex[n] in range(3)
 
     bitcoind.generate_block(1)
     sync_blockheight(bitcoind, [l1, l2, l3, l4])
 
     # l1 can't spent the output to addr.
-    assert not l1.daemon.is_in_log(r'Owning output.* \(SEGWIT\).* txid %s.* CONFIRMED' % closetxid[0])
+    for txid in closetxs.values():
-    assert not l1.daemon.is_in_log(r'Owning output.* \(SEGWIT\).* txid %s.* CONFIRMED' % closetxid[1])
+        assert not l1.daemon.is_in_log(r'Owning output.* \(SEGWIT\).* txid {}.* CONFIRMED'.format(txid))
-    assert not l1.daemon.is_in_log(r'Owning output.* \(SEGWIT\).* txid %s.* CONFIRMED' % closetxid[2])
+
     # Check the txid has at least 1 confirmation
-    l2.daemon.wait_for_log(r'Owning output.* \(SEGWIT\).* txid %s.* CONFIRMED' % closetxid[idindex[l2]])
+    for n, txid in closetxs.items():
-    l3.daemon.wait_for_log(r'Owning output.* \(SEGWIT\).* txid %s.* CONFIRMED' % closetxid[idindex[l3]])
+        n.daemon.wait_for_log(r'Owning output.* \(SEGWIT\).* txid {}.* CONFIRMED'.format(txid))
-    l4.daemon.wait_for_log(r'Owning output.* \(SEGWIT\).* txid %s.* CONFIRMED' % closetxid[idindex[l4]])
 
     for n in [l2, l3, l4]:
         # Make sure both nodes have grabbed their close tx funds
+        closetx = closetxs[n]
         outputs = n.rpc.listfunds()['outputs']
-        assert closetxid[idindex[n]] in set([o['txid'] for o in outputs])
+        assert closetx in set([o['txid'] for o in outputs])
-        output_num2 = [o for o in outputs if o['txid'] == closetxid[idindex[n]]][0]['output']
+        output_num2 = [o for o in outputs if o['txid'] == closetx][0]['output']
         output_num1 = 0 if output_num2 == 1 else 1
         # Check the another address is addr
-        assert addr == bitcoind.rpc.gettxout(closetxid[idindex[n]], output_num1)['scriptPubKey']['addresses'][0]
+        assert addr == bitcoind.rpc.gettxout(closetx, output_num1)['scriptPubKey']['addresses'][0]
-        assert 1 == bitcoind.rpc.gettxout(closetxid[idindex[n]], output_num1)['confirmations']
+        assert 1 == bitcoind.rpc.gettxout(closetx, output_num1)['confirmations']
 
 
 @unittest.skipIf(not COMPAT, "needs COMPAT=1")