Merge bitcoin/bitcoin#26733: test: Add test for sendmany rpc that uses subtractfeefrom parameter

057057a Add test for `sendmany` rpc that uses `subtractfeefrom` parameter (Yusuf Sahin HAMZA)

Pull request description:

  This PR adds test that uses `sendmany` rpc to send **BTC** to multiple addresses using `subtractfeefrom` parameter, then checks receiver addresses balances to make sure fees are subtracted correctly.

ACKs for top commit:
  achow101:
    ACK 057057a

Tree-SHA512: 51167120d489f0ff7b8b9855424d07cb55a8965984f904643cddf45e7a08c350eaded498c350ec9c660edf72c2f128ec142347c9c79d5043d9f6cd481b15cd7e

Author: achow101

test/functional/wallet_basic.py

@@ -267,6 +267,20 @@ def run_test(self):
         assert_equal(self.nodes[2].getbalance(), node_2_bal)
         node_0_bal = self.check_fee_amount(self.nodes[0].getbalance(), node_0_bal + Decimal('10'), fee_per_byte, self.get_vsize(self.nodes[2].gettransaction(txid)['hex']))
 
+        # Sendmany 5 BTC to two addresses with subtracting fee from both addresses
+        a0 = self.nodes[0].getnewaddress()
+        a1 = self.nodes[0].getnewaddress()
+        txid = self.nodes[2].sendmany(dummy='', amounts={a0: 5, a1: 5}, subtractfeefrom=[a0, a1])
+        self.generate(self.nodes[2], 1, sync_fun=lambda: self.sync_all(self.nodes[0:3]))
+        node_2_bal -= Decimal('10')
+        assert_equal(self.nodes[2].getbalance(), node_2_bal)
+        tx = self.nodes[2].gettransaction(txid)
+        node_0_bal = self.check_fee_amount(self.nodes[0].getbalance(), node_0_bal + Decimal('10'), fee_per_byte, self.get_vsize(tx['hex']))
+        assert_equal(self.nodes[0].getbalance(), node_0_bal)
+        expected_bal = Decimal('5') + (tx['fee'] / 2)
+        assert_equal(self.nodes[0].getreceivedbyaddress(a0), expected_bal)
+        assert_equal(self.nodes[0].getreceivedbyaddress(a1), expected_bal)
+
         self.log.info("Test sendmany with fee_rate param (explicit fee rate in sat/vB)")
         fee_rate_sat_vb = 2
         fee_rate_btc_kvb = fee_rate_sat_vb * 1e3 / 1e8