pytest: Add tests for htlc_accepted_hook

Two tests: one for failures and one for in-path resolution.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

tests/plugins/fail_htlcs.py

@@ -0,0 +1,15 @@
+#!/usr/bin/env python3
+
+from lightning import Plugin
+
+plugin = Plugin()
+
+
+@plugin.hook("htlc_accepted")
+def on_htlc_accepted(htlc, onion, plugin):
+    plugin.log("Failing htlc on purpose")
+    plugin.log("onion: %r" % (onion))
+    return {"result": "fail", "failure_code": 16399}
+
+
+plugin.run()

tests/plugins/shortcircuit.py

@@ -0,0 +1,13 @@
+#!/usr/bin/env python3
+
+from lightning import Plugin
+
+plugin = Plugin()
+
+
+@plugin.hook("htlc_accepted")
+def on_htlc_accepted(onion, htlc, plugin):
+    return {"result": "resolve", "payment_key": "00" * 32}
+
+
+plugin.run()

tests/test_plugin.py

@@ -331,3 +331,56 @@ def test_openchannel_hook(node_factory, bitcoind):
     l1.connect(l2)
     with pytest.raises(RpcError, match=r"I don't like odd amounts"):
         l1.rpc.fundchannel(l2.info['id'], 100001)
+
+
+def test_htlc_accepted_hook_fail(node_factory):
+    """Send payments from l1 to l2, but l2 just declines everything.
+
+    l2 is configured with a plugin that'll hook into htlc_accepted and
+    always return failures. The same should also work for forwarded
+    htlcs in the second half.
+
+    """
+    l1, l2, l3 = node_factory.line_graph(3, opts=[
+        {},
+        {'plugin': 'tests/plugins/fail_htlcs.py'},
+        {}
+    ], wait_for_announce=True)
+
+    # This must fail
+    inv = l2.rpc.invoice(1000, "lbl", "desc")['bolt11']
+    with pytest.raises(RpcError) as excinfo:
+        l1.rpc.pay(inv)
+    assert excinfo.value.error['data']['failcode'] == 16399
+    assert excinfo.value.error['data']['erring_index'] == 1
+
+    # And the invoice must still be unpaid
+    inv = l2.rpc.listinvoices("lbl")['invoices']
+    assert len(inv) == 1 and inv[0]['status'] == 'unpaid'
+
+    # Now try with forwarded HTLCs: l2 should still fail them
+    # This must fail
+    inv = l3.rpc.invoice(1000, "lbl", "desc")['bolt11']
+    with pytest.raises(RpcError) as excinfo:
+        l1.rpc.pay(inv)
+
+    # And the invoice must still be unpaid
+    inv = l3.rpc.listinvoices("lbl")['invoices']
+    assert len(inv) == 1 and inv[0]['status'] == 'unpaid'
+
+
+def test_htlc_accepted_hook_resolve(node_factory):
+    """l3 creates an invoice, l2 knows the preimage and will shortcircuit.
+    """
+    l1, l2, l3 = node_factory.line_graph(3, opts=[
+        {},
+        {'plugin': 'tests/plugins/shortcircuit.py'},
+        {}
+    ], wait_for_announce=True)
+
+    inv = l3.rpc.invoice(msatoshi=1000, label="lbl", description="desc", preimage="00" * 32)['bolt11']
+    l1.rpc.pay(inv)
+
+    # And the invoice must still be unpaid
+    inv = l3.rpc.listinvoices("lbl")['invoices']
+    assert len(inv) == 1 and inv[0]['status'] == 'unpaid'