[wallet] Add rpc tests to verify fee calculations

qa/rpc-tests/test_framework/util.py

@@ -67,6 +67,9 @@ def check_json_precision():
     if satoshis != 2000000000000003:
         raise RuntimeError("JSON encode/decode loses precision")
 
+def count_bytes(hex_string):
+    return len(bytearray.fromhex(hex_string))
+
 def sync_blocks(rpc_connections, wait=1):
     """
     Wait until everybody has the same block count

qa/rpc-tests/wallet.py

@@ -24,6 +24,17 @@
 
 class WalletTest (BitcoinTestFramework):
 
+    def check_fee_amount(self, curr_balance, balance_with_fee, fee_per_byte, tx_size):
+        """Return curr_balance after asserting the fee was in range"""
+        fee = balance_with_fee - curr_balance
+        target_fee = fee_per_byte * tx_size
+        if fee < target_fee:
+            raise AssertionError("Fee of %s BTC too low! (Should be %s BTC)"%(str(fee), str(target_fee)))
+        # allow the node's estimation to be at most 2 bytes off
+        if fee > fee_per_byte * (tx_size + 2):
+            raise AssertionError("Fee of %s BTC too high! (Should be %s BTC)"%(str(fee), str(target_fee)))
+        return curr_balance
+
     def setup_chain(self):
         print("Initializing test directory "+self.options.tmpdir)
         initialize_chain_clean(self.options.tmpdir, 4)
@@ -104,33 +115,37 @@ def run_test (self):
 
         # Send 10 BTC normal
         address = self.nodes[0].getnewaddress("test")
-        self.nodes[2].settxfee(Decimal('0.001'))
+        fee_per_byte = Decimal('0.001') / 1000
+        self.nodes[2].settxfee(fee_per_byte * 1000)
         txid = self.nodes[2].sendtoaddress(address, 10, "", "", False)
         self.nodes[2].generate(1)
         self.sync_all()
-        assert_equal(self.nodes[2].getbalance(), Decimal('89.99900000'))
-        assert_equal(self.nodes[0].getbalance(), Decimal('10.00000000'))
+        node_2_bal = self.check_fee_amount(self.nodes[2].getbalance(), Decimal('90'), fee_per_byte, count_bytes(self.nodes[2].getrawtransaction(txid)))
+        assert_equal(self.nodes[0].getbalance(), Decimal('10'))
 
         # Send 10 BTC with subtract fee from amount
         txid = self.nodes[2].sendtoaddress(address, 10, "", "", True)
         self.nodes[2].generate(1)
         self.sync_all()
-        assert_equal(self.nodes[2].getbalance(), Decimal('79.99900000'))
-        assert_equal(self.nodes[0].getbalance(), Decimal('19.99900000'))
+        node_2_bal -= Decimal('10')
+        assert_equal(self.nodes[2].getbalance(), node_2_bal)
+        node_0_bal = self.check_fee_amount(self.nodes[0].getbalance(), Decimal('20'), fee_per_byte, count_bytes(self.nodes[2].getrawtransaction(txid)))
 
         # Sendmany 10 BTC
         txid = self.nodes[2].sendmany('from1', {address: 10}, 0, "", [])
         self.nodes[2].generate(1)
         self.sync_all()
-        assert_equal(self.nodes[2].getbalance(), Decimal('69.99800000'))
-        assert_equal(self.nodes[0].getbalance(), Decimal('29.99900000'))
+        node_0_bal += Decimal('10')
+        node_2_bal = self.check_fee_amount(self.nodes[2].getbalance(), node_2_bal - Decimal('10'), fee_per_byte, count_bytes(self.nodes[2].getrawtransaction(txid)))
+        assert_equal(self.nodes[0].getbalance(), node_0_bal)
 
         # Sendmany 10 BTC with subtract fee from amount
         txid = self.nodes[2].sendmany('from1', {address: 10}, 0, "", [address])
         self.nodes[2].generate(1)
         self.sync_all()
-        assert_equal(self.nodes[2].getbalance(), Decimal('59.99800000'))
-        assert_equal(self.nodes[0].getbalance(), Decimal('39.99800000'))
+        node_2_bal -= Decimal('10')
+        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, count_bytes(self.nodes[2].getrawtransaction(txid)))
 
         # Test ResendWalletTransactions:
         # Create a couple of transactions, then start up a fourth
@@ -191,14 +206,14 @@ def run_test (self):
         txObjNotBroadcasted = self.nodes[0].gettransaction(txIdNotBroadcasted)
         self.nodes[1].generate(1) #mine a block, tx should not be in there
         self.sync_all()
-        assert_equal(self.nodes[2].getbalance(), Decimal('59.99800000')); #should not be changed because tx was not broadcasted
+        assert_equal(self.nodes[2].getbalance(), node_2_bal); #should not be changed because tx was not broadcasted
 
         #now broadcast from another node, mine a block, sync, and check the balance
         self.nodes[1].sendrawtransaction(txObjNotBroadcasted['hex'])
         self.nodes[1].generate(1)
         self.sync_all()
         txObjNotBroadcasted = self.nodes[0].gettransaction(txIdNotBroadcasted)
-        assert_equal(self.nodes[2].getbalance(), Decimal('61.99800000')); #should not be
+        assert_equal(self.nodes[2].getbalance(), node_2_bal + Decimal('2')); #should not be
 
         #create another tx
         txIdNotBroadcasted  = self.nodes[0].sendtoaddress(self.nodes[2].getnewaddress(), 2);
@@ -216,7 +231,7 @@ def run_test (self):
         sync_blocks(self.nodes)
 
         #tx should be added to balance because after restarting the nodes tx should be broadcastet
-        assert_equal(self.nodes[2].getbalance(), Decimal('63.99800000')); #should not be
+        assert_equal(self.nodes[2].getbalance(), node_2_bal + Decimal('4')); #should not be
 
         #send a tx with value in a string (PR#6380 +)
         txId  = self.nodes[0].sendtoaddress(self.nodes[2].getnewaddress(), "2")