test: test the implicit avoid partial spends functionality

Co-authored-by: Fabian Jahr <[email protected]>

Author: kallewoof

test/functional/wallet_groups.py

@@ -15,8 +15,8 @@
 class WalletGroupTest(BitcoinTestFramework):
     def set_test_params(self):
         self.setup_clean_chain = True
-        self.num_nodes = 3
-        self.extra_args = [[], [], ['-avoidpartialspends']]
+        self.num_nodes = 4
+        self.extra_args = [[], [], ['-avoidpartialspends'], ["-maxapsfee=0.0001"]]
         self.rpc_timeout = 480
 
     def skip_test_if_missing_module(self):
@@ -64,6 +64,52 @@ def run_test(self):
         assert_approx(v[0], 0.2)
         assert_approx(v[1], 1.3, 0.0001)
 
+        # Test 'avoid partial if warranted, even if disabled'
+        self.sync_all()
+        self.nodes[0].generate(1)
+        # Nodes 1-2 now have confirmed UTXOs (letters denote destinations):
+        # Node #1:      Node #2:
+        # - A  1.0      - D0 1.0
+        # - B0 1.0      - D1 0.5
+        # - B1 0.5      - E0 1.0
+        # - C0 1.0      - E1 0.5
+        # - C1 0.5      - F  ~1.3
+        # - D ~0.3
+        assert_approx(self.nodes[1].getbalance(), 4.3, 0.0001)
+        assert_approx(self.nodes[2].getbalance(), 4.3, 0.0001)
+        # Sending 1.4 btc should pick one 1.0 + one more. For node #1,
+        # this could be (A / B0 / C0) + (B1 / C1 / D). We ensure that it is
+        # B0 + B1 or C0 + C1, because this avoids partial spends while not being
+        # detrimental to transaction cost
+        txid3 = self.nodes[1].sendtoaddress(self.nodes[0].getnewaddress(), 1.4)
+        tx3 = self.nodes[1].getrawtransaction(txid3, True)
+        # tx3 should have 2 inputs and 2 outputs
+        assert_equal(2, len(tx3["vin"]))
+        assert_equal(2, len(tx3["vout"]))
+        # the accumulated value should be 1.5, so the outputs should be
+        # ~0.1 and 1.4 and should come from the same destination
+        values = [vout["value"] for vout in tx3["vout"]]
+        values.sort()
+        assert_approx(values[0], 0.1, 0.0001)
+        assert_approx(values[1], 1.4)
+
+        input_txids = [vin["txid"] for vin in tx3["vin"]]
+        input_addrs = [self.nodes[1].gettransaction(txid)['details'][0]['address'] for txid in input_txids]
+        assert_equal(input_addrs[0], input_addrs[1])
+        # Node 2 enforces avoidpartialspends so needs no checking here
+
+        # Test wallet option maxapsfee with Node 3
+        addr_aps = self.nodes[3].getnewaddress()
+        self.nodes[0].sendtoaddress(addr_aps, 1.0)
+        self.nodes[0].sendtoaddress(addr_aps, 1.0)
+        self.nodes[0].generate(1)
+        txid4 = self.nodes[3].sendtoaddress(self.nodes[0].getnewaddress(), 0.1)
+        tx4 = self.nodes[3].getrawtransaction(txid4, True)
+        # tx4 should have 2 inputs and 2 outputs although one output would
+        # have been enough and the transaction caused higher fees
+        assert_equal(2, len(tx4["vin"]))
+        assert_equal(2, len(tx4["vout"]))
+
         # Empty out node2's wallet
         self.nodes[2].sendtoaddress(address=self.nodes[0].getnewaddress(), amount=self.nodes[2].getbalance(), subtractfeefromamount=True)
         self.sync_all()