tests: add TestLNWallet to test lnwallet utils

Adds new unittest file test_lnwallet.py to allow unittesting
utility functions of LNWallet.

tests/test_lnwallet.py

@@ -0,0 +1,45 @@
+import logging
+import os
+
+from . import ElectrumTestCase
+
+from electrum.lnutil import RECEIVED, MIN_FINAL_CLTV_DELTA_ACCEPTED
+from electrum.logging import console_stderr_handler
+from electrum.invoices import LN_EXPIRY_NEVER, PR_UNPAID
+
+
+class TestLNWallet(ElectrumTestCase):
+    TESTNET = True
+
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        console_stderr_handler.setLevel(logging.DEBUG)
+
+    async def asyncSetUp(self):
+        self.lnwallet_anchors = self.create_mock_lnwallet(name='mock_lnwallet_anchors', has_anchors=True)
+        await super().asyncSetUp()
+
+    def test_create_payment_info(self):
+        wallet = self.lnwallet_anchors
+        tests = (
+            (100_000, 200, 100),
+            (0, 200, 100),
+            (None, 200, 100),
+            (None, None, LN_EXPIRY_NEVER),
+            (100_000, None, 0),
+        )
+        for amount_msat, min_final_cltv_delta, exp_delay in tests:
+            payment_hash = wallet.create_payment_info(
+                amount_msat=amount_msat,
+                min_final_cltv_delta=min_final_cltv_delta,
+                exp_delay=exp_delay,
+            )
+            self.assertIsNotNone(wallet.get_preimage(payment_hash))
+            pi = wallet.get_payment_info(payment_hash, direction=RECEIVED)
+            self.assertEqual(pi.amount_msat, amount_msat)
+            self.assertEqual(pi.min_final_cltv_delta, min_final_cltv_delta or MIN_FINAL_CLTV_DELTA_ACCEPTED)
+            self.assertEqual(pi.expiry_delay, exp_delay or LN_EXPIRY_NEVER)
+            self.assertEqual(pi.db_key, f"{payment_hash.hex()}:{int(pi.direction)}")
+            self.assertEqual(pi.status, PR_UNPAID)
+        self.assertIsNone(wallet.get_payment_info(os.urandom(32), direction=RECEIVED))