tests: introduce a lianad_multipath fixture as well as a trivial test

tests/fixtures.py

@@ -189,3 +189,37 @@ def lianad_multisig(bitcoind, directory):
         raise
 
     lianad.cleanup()
+
+
+@pytest.fixture
+def lianad_multipath(bitcoind, directory):
+    datadir = os.path.join(directory, "lianad")
+    os.makedirs(datadir, exist_ok=True)
+    bitcoind_cookie = os.path.join(bitcoind.bitcoin_dir, "regtest", ".cookie")
+
+    # A 3-of-4 that degrades into a 3-of-5 after 10 blocks and into a 1-of-10 after 20 blocks.
+    csv_values = [10, 20]
+    signer = MultiSigner(4, {csv_values[0]: 5, csv_values[1]: 10})
+    prim_multi = multi_expression(3, signer.prim_hds)
+    first_recov_multi = multi_expression(3, signer.recov_hds[csv_values[0]])
+    second_recov_multi = multi_expression(1, signer.recov_hds[csv_values[1]])
+    main_desc = Descriptor.from_str(
+        f"wsh(or_d({prim_multi},or_i(and_v(v:{first_recov_multi},older({csv_values[0]})),and_v(v:{second_recov_multi},older({csv_values[1]})))))"
+    )
+
+    lianad = Lianad(
+        datadir,
+        signer,
+        main_desc,
+        bitcoind.rpcport,
+        bitcoind_cookie,
+    )
+
+    try:
+        lianad.start()
+        yield lianad
+    except Exception:
+        lianad.cleanup()
+        raise
+
+    lianad.cleanup()

tests/test_misc.py

@@ -75,6 +75,12 @@ def test_multisig(lianad_multisig, bitcoind):
     lianad_multisig.rpc.broadcastspend(txid)
 
 
+def test_multipath(lianad_multipath, bitcoind):
+    """Exercise various commands as well as recovery with a descriptor with multiple
+    recovery paths."""
+    receive_and_send(lianad_multipath, bitcoind)
+
+
 def test_coinbase_deposit(lianad, bitcoind):
     """Check we detect deposits from (mature) coinbase transactions."""
     # Create a new deposit in a coinbase transaction.