Merge #20220: wallet, rpc: explicit fee rate follow-ups/fixes for 0.21

0be29000c011dec0722481dbebb159873da6fa54 rpc: update conf_target helps for correctness/consistency (Jon Atack)
778b9be40667876c705e586849ea9c9e44cf451c wallet, rpc: fix send subtract_fee_from_outputs help (Jon Atack)
603c0050837ec65765208dd54dde354145fbe098 wallet: add rpc send explicit fee rate coverage (Jon Atack)
dd341e602d5160fc621c0299179b91403756b61d wallet: add sendtoaddress/sendmany explicit fee rate coverage (Jon Atack)
44e7bfa60313e4ae67da49e5ba4535038b71b453 wallet: add walletcreatefundedpsbt explicit fee rate coverage (Jon Atack)
6e1ea4273e52fdcd86c87628aa595c03a071ca8c test: refactor for walletcreatefundedpsbt fee rate coverage (Jon Atack)
3ac7b0c6f1c68e74a84d868a454f508bada6b09d wallet: fundrawtx fee rate coverage, fixup ParseConfirmTarget() (Jon Atack)
2d8eba8f8425a2515022d51f1f5b4911329fbf55 wallet: combine redundant bumpfee invalid params and args tests (Jon Atack)
1697a40b6f841a54ee0d9744ed7fd09034b0ddad wallet: improve bumpfee error/help, add explicit fee rate coverage (Jon Atack)
fc5721723d34f76f9e1ffd2e31f274ea6b22f894 wallet: fix SetFeeEstimateMode() error message (Jon Atack)
052427eef1c9da84c474c5161b1910d3328ef0da wallet, bugfix: fix bumpfee with explicit fee rate modes (Jon Atack)

Pull request description:

  Follow-up to #11413 providing a base to build on for #19543:

  - bugfix for `bumpfee` raising a JSON error with explicit feerates, fixes issue #20219
  - adds explicit feerate test coverage for `bumpfee`, `fundrawtransaction`, `walletcreatefundedpsbt`, `send`, `sendtoaddress`, and `sendmany`
  - improves a few related RPC error messages and `ParseConfirmTarget()` / error message
  - fixes/improves the explicit fee rate information in the 6 RPC helps, of which 2 were also missing `conf_target` sat/B units

  This provides a spec and regression coverage for the potential next step of a universal `sat/vB` feerate argument (see #19543), as well as immediate coverage and minimum fixes for 0.21.

ACKs for top commit:
  kallewoof:
    Concept/Tested ACK 0be29000c011dec0722481dbebb159873da6fa54
  meshcollider:
    Code review + functional test run ACK 0be29000c011dec0722481dbebb159873da6fa54

Tree-SHA512: efd965003e991cba51d4504e2940f06ab3d742e34022e96a673606b44fad85596aa03a8c1809f06df7ebcf21a38e18a891e54392fe3d6fb4d120bbe4ea0cf5e0

7 files changed, 282 insertions, 95 deletions

diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index 40dfdb587e..1b21587b6d 100644
--- a/src/rpc/util.cpp
+++ b/src/rpc/util.cpp
@@ -272,11 +272,12 @@ UniValue DescribeAddress(const CTxDestination& dest)
 
 unsigned int ParseConfirmTarget(const UniValue& value, unsigned int max_target)
 {
-    int target = value.get_int();
-    if (target < 1 || (unsigned int)target > max_target) {
-        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid conf_target, must be between %u - %u", 1, max_target));
+    const int target{value.get_int()};
+    const unsigned int unsigned_target{static_cast<unsigned int>(target)};
+    if (target < 1 || unsigned_target > max_target) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid conf_target, must be between %u and %u", 1, max_target));
     }
-    return (unsigned int)target;
+    return unsigned_target;
 }
 
 RPCErrorCode RPCErrorFromTransactionError(TransactionError terr)
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 8aaa03e0c9..ebcab1227d 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -214,7 +214,7 @@ static void SetFeeEstimateMode(const CWallet* pwallet, CCoinControl& cc, const U
 
     if (cc.m_fee_mode == FeeEstimateMode::BTC_KB || cc.m_fee_mode == FeeEstimateMode::SAT_B) {
         if (estimate_param.isNull()) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "Selected estimate_mode requires a fee rate");
+            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Selected estimate_mode %s requires a fee rate to be specified in conf_target", estimate_mode.get_str()));
         }
 
         CAmount fee_rate = AmountFromValue(estimate_param);
@@ -440,7 +440,8 @@ static RPCHelpMan sendtoaddress()
                     {"subtractfeefromamount", RPCArg::Type::BOOL, /* default */ "false", "The fee will be deducted from the amount being sent.\n"
                                          "The recipient will receive less bitcoins than you enter in the amount field."},
                     {"replaceable", RPCArg::Type::BOOL, /* default */ "wallet default", "Allow this transaction to be replaced by a transaction with higher fees via BIP 125"},
-                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet default", "Confirmation target (in blocks), or fee rate (for " + CURRENCY_UNIT + "/kB or " + CURRENCY_ATOM + "/B estimate modes)"},
+                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
+                                         "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
                     {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
             "       \"" + FeeModes("\"\n\"") + "\""},
                     {"avoid_reuse", RPCArg::Type::BOOL, /* default */ "true", "(only available if avoid_reuse wallet flag is set) Avoid spending from dirty addresses; addresses are considered\n"
@@ -868,7 +869,8 @@ static RPCHelpMan sendmany()
                         },
                     },
                     {"replaceable", RPCArg::Type::BOOL, /* default */ "wallet default", "Allow this transaction to be replaced by a transaction with higher fees via BIP 125"},
-                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet default", "Confirmation target (in blocks), or fee rate (for " + CURRENCY_UNIT + "/kB or " + CURRENCY_ATOM + "/B estimate modes)"},
+                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
+                                       "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
                     {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
             "       \"" + FeeModes("\"\n\"") + "\""},
                     {"verbose", RPCArg::Type::BOOL, /* default */ "false", "If true, return extra infomration about the transaction."},
@@ -3044,7 +3046,7 @@ static RPCHelpMan listunspent()
     };
 }
 
-void FundTransaction(CWallet* const pwallet, CMutableTransaction& tx, CAmount& fee_out, int& change_position, UniValue options, CCoinControl& coinControl)
+void FundTransaction(CWallet* const pwallet, CMutableTransaction& tx, CAmount& fee_out, int& change_position, const UniValue& options, CCoinControl& coinControl)
 {
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
@@ -3210,7 +3212,8 @@ static RPCHelpMan fundrawtransaction()
                             },
                             {"replaceable", RPCArg::Type::BOOL, /* default */ "wallet default", "Marks this transaction as BIP125 replaceable.\n"
                                                           "Allows this transaction to be replaced by a transaction with higher fees"},
-                            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet default", "Confirmation target (in blocks), or fee rate (for " + CURRENCY_UNIT + "/kB or " + CURRENCY_ATOM + "/B estimate modes)"},
+                            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
+                                                          "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
                             {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
                             "       \"" + FeeModes("\"\n\"") + "\""},
                         },
@@ -3378,7 +3381,7 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
         "The command will pay the additional fee by reducing change outputs or adding inputs when necessary. It may add a new change output if one does not already exist.\n"
         "All inputs in the original transaction will be included in the replacement transaction.\n"
         "The command will fail if the wallet or mempool contains a transaction that spends one of T's outputs.\n"
-        "By default, the new fee will be calculated automatically using estimatesmartfee.\n"
+        "By default, the new fee will be calculated automatically using the estimatesmartfee RPC.\n"
         "The user can specify a confirmation target for estimatesmartfee.\n"
         "Alternatively, the user can specify a fee_rate (" + CURRENCY_UNIT + " per kB) for the new transaction.\n"
         "At a minimum, the new fee rate must be high enough to pay an additional new relay fee (incrementalfee\n"
@@ -3387,10 +3390,11 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
             {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The txid to be bumped"},
             {"options", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED_NAMED_ARG, "",
                 {
-                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet default", "Confirmation target (in blocks)"},
-                    {"fee_rate", RPCArg::Type::NUM, /* default */ "fall back to 'conf_target'", "fee rate (NOT total fee) to pay, in " + CURRENCY_UNIT + " per kB\n"
+                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
+                             "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
+                    {"fee_rate", RPCArg::Type::NUM, /* default */ "fall back to 'conf_target'", "fee rate (NOT total fee) to pay, in " + CURRENCY_UNIT + "/kB.\n"
                              "Specify a fee rate instead of relying on the built-in fee estimator.\n"
-                             "Must be at least 0.0001 " + CURRENCY_UNIT + " per kB higher than the current transaction fee rate.\n"},
+                             "Must be at least 0.0001 " + CURRENCY_UNIT + "/kB higher than the current transaction fee rate.\n"},
                     {"replaceable", RPCArg::Type::BOOL, /* default */ "true", "Whether the new transaction should still be\n"
                              "marked bip-125 replaceable. If true, the sequence numbers in the transaction will\n"
                              "be left unchanged from the original. If false, any input sequence numbers in the\n"
@@ -3464,9 +3468,8 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
 
         if (!conf_target.isNull()) {
             if (options.exists("fee_rate")) {
-                throw JSONRPCError(RPC_INVALID_PARAMETER, "conf_target can't be set with fee_rate. Please provide either a confirmation target in blocks for automatic fee estimation, or an explicit fee rate.");
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both conf_target and fee_rate. Please provide either a confirmation target in blocks for automatic fee estimation, or an explicit fee rate.");
             }
-            coin_control.m_confirm_target = ParseConfirmTarget(conf_target, pwallet->chain().estimateMaxBlocks());
         } else if (options.exists("fee_rate")) {
             CFeeRate fee_rate(AmountFromValue(options["fee_rate"]));
             if (fee_rate <= CFeeRate(0)) {
@@ -4014,7 +4017,8 @@ static RPCHelpMan send()
                     },
                 },
             },
-            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet default", "Confirmation target (in blocks), or fee rate (for " + CURRENCY_UNIT + "/kB or " + CURRENCY_ATOM + "/B estimate modes)"},
+            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
+                    "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
             {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
                         "       \"" + FeeModes("\"\n\"") + "\""},
             {"options", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED_NAMED_ARG, "",
@@ -4024,7 +4028,8 @@ static RPCHelpMan send()
                     {"change_address", RPCArg::Type::STR_HEX, /* default */ "pool address", "The bitcoin address to receive the change"},
                     {"change_position", RPCArg::Type::NUM, /* default */ "random", "The index of the change output"},
                     {"change_type", RPCArg::Type::STR, /* default */ "set by -changetype", "The output type to use. Only valid if change_address is not specified. Options are \"legacy\", \"p2sh-segwit\", and \"bech32\"."},
-                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet default", "Confirmation target (in blocks), or fee rate (for " + CURRENCY_UNIT + "/kB or " + CURRENCY_ATOM + "/B estimate modes)"},
+                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
+                            "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
                     {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
             "       \"" + FeeModes("\"\n\"") + "\""},
                     {"include_watching", RPCArg::Type::BOOL, /* default */ "true for watch-only wallets, otherwise false", "Also select inputs which are watch only.\n"
@@ -4040,7 +4045,7 @@ static RPCHelpMan send()
                     {"locktime", RPCArg::Type::NUM, /* default */ "0", "Raw locktime. Non-0 value also locktime-activates inputs"},
                     {"lock_unspents", RPCArg::Type::BOOL, /* default */ "false", "Lock selected unspent outputs"},
                     {"psbt", RPCArg::Type::BOOL,  /* default */ "automatic", "Always return a PSBT, implies add_to_wallet=false."},
-                    {"subtract_fee_from_outputs", RPCArg::Type::ARR, /* default */ "empty array", "A JSON array of integers.\n"
+                    {"subtract_fee_from_outputs", RPCArg::Type::ARR, /* default */ "empty array", "Outputs to subtract the fee from, specified as integer indices.\n"
                     "The fee will be equally deducted from the amount of each specified output.\n"
                     "Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
                     "If no outputs are specified here, the sender pays the fee.",
@@ -4121,7 +4126,7 @@ static RPCHelpMan send()
             CMutableTransaction rawTx = ConstructTransaction(options["inputs"], request.params[0], options["locktime"], rbf);
             CCoinControl coin_control;
             // Automatically select coins, unless at least one is manually selected. Can
-            // be overriden by options.add_inputs.
+            // be overridden by options.add_inputs.
             coin_control.m_add_inputs = rawTx.vin.size() == 0;
             FundTransaction(pwallet, rawTx, fee, change_position, options, coin_control);
 
@@ -4362,7 +4367,8 @@ static RPCHelpMan walletcreatefundedpsbt()
                             },
                             {"replaceable", RPCArg::Type::BOOL, /* default */ "wallet default", "Marks this transaction as BIP125 replaceable.\n"
                                                           "Allows this transaction to be replaced by a transaction with higher fees"},
-                            {"conf_target", RPCArg::Type::NUM, /* default */ "fall back to wallet's confirmation target (txconfirmtarget)", "Confirmation target (in blocks)"},
+                            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
+                                                          "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
                             {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
                             "         \"" + FeeModes("\"\n\"") + "\""},
                         },
diff --git a/test/functional/rpc_fundrawtransaction.py b/test/functional/rpc_fundrawtransaction.py
index 5a23b60dd8..503993162b 100755
--- a/test/functional/rpc_fundrawtransaction.py
+++ b/test/functional/rpc_fundrawtransaction.py
@@ -8,6 +8,7 @@ from decimal import Decimal
 from test_framework.descriptors import descsum_create
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
+    assert_approx,
     assert_equal,
     assert_fee_amount,
     assert_greater_than,
@@ -89,6 +90,7 @@ class RawTransactionsTest(BitcoinTestFramework):
         self.test_op_return()
         self.test_watchonly()
         self.test_all_watched_funds()
+        self.test_feerate_with_conf_target_and_estimate_mode()
         self.test_option_feerate()
         self.test_address_reuse()
         self.test_option_subtract_fee_from_outputs()
@@ -722,6 +724,59 @@ class RawTransactionsTest(BitcoinTestFramework):
         assert_fee_amount(result2['fee'], count_bytes(result2['hex']), 2 * result_fee_rate)
         assert_fee_amount(result3['fee'], count_bytes(result3['hex']), 10 * result_fee_rate)
 
+    def test_feerate_with_conf_target_and_estimate_mode(self):
+        self.log.info("Test fundrawtxn passing an explicit fee rate using conf_target and estimate_mode")
+        node = self.nodes[3]
+        # Make sure there is exactly one input so coin selection can't skew the result.
+        assert_equal(len(node.listunspent(1)), 1)
+        inputs = []
+        outputs = {node.getnewaddress() : 1}
+        rawtx = node.createrawtransaction(inputs, outputs)
+
+        for unit, fee_rate in {"btc/kb": 0.1, "sat/b": 10000}.items():
+            self.log.info("Test fundrawtxn with conf_target {} estimate_mode {} produces expected fee".format(fee_rate, unit))
+            # With no arguments passed, expect fee of 141 sats/b.
+            assert_approx(node.fundrawtransaction(rawtx)["fee"], vexp=0.00000141, vspan=0.00000001)
+            # Expect fee to be 10,000x higher when explicit fee 10,000x greater is specified.
+            result = node.fundrawtransaction(rawtx, {"conf_target": fee_rate, "estimate_mode": unit})
+            assert_approx(result["fee"], vexp=0.0141, vspan=0.0001)
+
+        for field, fee_rate in {"conf_target": 0.1, "estimate_mode": "sat/b"}.items():
+            self.log.info("Test fundrawtxn raises RPC error if both feeRate and {} are passed".format(field))
+            assert_raises_rpc_error(
+                -8, "Cannot specify both {} and feeRate".format(field),
+                lambda: node.fundrawtransaction(rawtx, {"feeRate": 0.1, field: fee_rate}))
+
+        self.log.info("Test fundrawtxn with invalid estimate_mode settings")
+        for k, v in {"number": 42, "object": {"foo": "bar"}}.items():
+            assert_raises_rpc_error(-3, "Expected type string for estimate_mode, got {}".format(k),
+                lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": v, "conf_target": 0.1}))
+        for mode in ["foo", Decimal("3.141592")]:
+            assert_raises_rpc_error(-8, "Invalid estimate_mode parameter",
+                lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": 0.1}))
+
+        self.log.info("Test fundrawtxn with invalid conf_target settings")
+        for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
+            self.log.debug("{}".format(mode))
+            for k, v in {"string": "", "object": {"foo": "bar"}}.items():
+                assert_raises_rpc_error(-3, "Expected type number for conf_target, got {}".format(k),
+                    lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": v}))
+            if mode in ["btc/kb", "sat/b"]:
+                assert_raises_rpc_error(-3, "Amount out of range",
+                    lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": -1}))
+                assert_raises_rpc_error(-4, "Fee rate (0.00000000 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
+                    lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": 0}))
+            else:
+                for n in [-1, 0, 1009]:
+                    assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",
+                        lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": n}))
+
+        for unit, fee_rate in {"sat/B": 0.99999999, "BTC/kB": 0.00000999}.items():
+            self.log.info("- raises RPC error 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
+            assert_raises_rpc_error(-4, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
+                lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": unit, "conf_target": fee_rate, "add_inputs": True}))
+
+
     def test_address_reuse(self):
         """Test no address reuse occurs."""
         self.log.info("Test fundrawtxn does not reuse addresses")
diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
index 32dc2f8644..ca75bcb9bb 100755
--- a/test/functional/rpc_psbt.py
+++ b/test/functional/rpc_psbt.py
@@ -172,8 +172,11 @@ class PSBTTest(BitcoinTestFramework):
             elif out['scriptPubKey']['addresses'][0] == p2pkh:
                 p2pkh_pos = out['n']
 
+        inputs = [{"txid": txid, "vout": p2wpkh_pos}, {"txid": txid, "vout": p2sh_p2wpkh_pos}, {"txid": txid, "vout": p2pkh_pos}]
+        outputs = [{self.nodes[1].getnewaddress(): 29.99}]
+
         # spend single key from node 1
-        created_psbt = self.nodes[1].walletcreatefundedpsbt([{"txid":txid,"vout":p2wpkh_pos},{"txid":txid,"vout":p2sh_p2wpkh_pos},{"txid":txid,"vout":p2pkh_pos}], {self.nodes[1].getnewaddress():29.99})
+        created_psbt = self.nodes[1].walletcreatefundedpsbt(inputs, outputs)
         walletprocesspsbt_out = self.nodes[1].walletprocesspsbt(created_psbt['psbt'])
         # Make sure it has both types of UTXOs
         decoded = self.nodes[1].decodepsbt(walletprocesspsbt_out['psbt'])
@@ -184,15 +187,62 @@ class PSBTTest(BitcoinTestFramework):
         assert_equal(walletprocesspsbt_out['complete'], True)
         self.nodes[1].sendrawtransaction(self.nodes[1].finalizepsbt(walletprocesspsbt_out['psbt'])['hex'])
 
-        # feeRate of 0.1 BTC / KB produces a total fee slightly below -maxtxfee (~0.05280000):
-        res = self.nodes[1].walletcreatefundedpsbt([{"txid":txid,"vout":p2wpkh_pos},{"txid":txid,"vout":p2sh_p2wpkh_pos},{"txid":txid,"vout":p2pkh_pos}], {self.nodes[1].getnewaddress():29.99}, 0, {"feeRate": 0.1, "add_inputs": True})
+        self.log.info("Test walletcreatefundedpsbt feeRate of 0.1 BTC/kB produces a total fee at or slightly below -maxtxfee (~0.05290000)")
+        res = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"feeRate": 0.1, "add_inputs": True})
         assert_approx(res["fee"], 0.055, 0.005)
 
-        # feeRate of 10 BTC / KB produces a total fee well above -maxtxfee
+        self.log.info("Test walletcreatefundedpsbt explicit fee rate with conf_target and estimate_mode")
+        for unit, fee_rate in {"btc/kb": 0.1, "sat/b": 10000}.items():
+            fee = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"conf_target": fee_rate, "estimate_mode": unit, "add_inputs": True})["fee"]
+            self.log.info("- conf_target {}, estimate_mode {} produces fee {} at or slightly below -maxtxfee (~0.05290000)".format(fee_rate, unit, fee))
+            assert_approx(fee, vexp=0.055, vspan=0.005)
+
+        for field, fee_rate in {"conf_target": 0.1, "estimate_mode": "sat/b"}.items():
+            self.log.info("- raises RPC error if both feeRate and {} are passed".format(field))
+            assert_raises_rpc_error(-8, "Cannot specify both {} and feeRate".format(field),
+                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"feeRate": 0.1, field: fee_rate, "add_inputs": True}))
+
+        self.log.info("- raises RPC error with invalid estimate_mode settings")
+        for k, v in {"number": 42, "object": {"foo": "bar"}}.items():
+            assert_raises_rpc_error(-3, "Expected type string for estimate_mode, got {}".format(k),
+                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": v, "conf_target": 0.1, "add_inputs": True}))
+        for mode in ["foo", Decimal("3.141592")]:
+            assert_raises_rpc_error(-8, "Invalid estimate_mode parameter",
+                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": 0.1, "add_inputs": True}))
+
+        self.log.info("- raises RPC error if estimate_mode is passed without a conf_target")
+        for unit in ["SAT/B", "BTC/KB"]:
+            assert_raises_rpc_error(-8, "Selected estimate_mode {} requires a fee rate to be specified in conf_target".format(unit),
+                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": unit}))
+
+        self.log.info("- raises RPC error with invalid conf_target settings")
+        for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
+            self.log.debug("{}".format(mode))
+            for k, v in {"string": "", "object": {"foo": "bar"}}.items():
+                assert_raises_rpc_error(-3, "Expected type number for conf_target, got {}".format(k),
+                    lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": v, "add_inputs": True}))
+            if mode in ["btc/kb", "sat/b"]:
+                assert_raises_rpc_error(-3, "Amount out of range",
+                    lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": -1, "add_inputs": True}))
+                assert_raises_rpc_error(-4, "Fee rate (0.00000000 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
+                    lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": 0, "add_inputs": True}))
+            else:
+                for n in [-1, 0, 1009]:
+                    assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",
+                        lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": n, "add_inputs": True}))
+
+        for unit, fee_rate in {"SAT/B": 0.99999999, "BTC/KB": 0.00000999}.items():
+            self.log.info("- raises RPC error 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
+            assert_raises_rpc_error(-4, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
+                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": unit, "conf_target": fee_rate, "add_inputs": True}))
+
+        self.log.info("Test walletcreatefundedpsbt feeRate of 10 BTC/kB produces total fee well above -maxtxfee and raises RPC error")
         # previously this was silently capped at -maxtxfee
-        assert_raises_rpc_error(-4, "Fee exceeds maximum configured by user (e.g. -maxtxfee, maxfeerate)", self.nodes[1].walletcreatefundedpsbt, [{"txid":txid,"vout":p2wpkh_pos},{"txid":txid,"vout":p2sh_p2wpkh_pos},{"txid":txid,"vout":p2pkh_pos}], {self.nodes[1].getnewaddress():29.99}, 0, {"feeRate": 10, "add_inputs": True})
-        assert_raises_rpc_error(-4, "Fee exceeds maximum configured by user (e.g. -maxtxfee, maxfeerate)", self.nodes[1].walletcreatefundedpsbt, [{"txid":txid,"vout":p2wpkh_pos},{"txid":txid,"vout":p2sh_p2wpkh_pos},{"txid":txid,"vout":p2pkh_pos}], {self.nodes[1].getnewaddress():1}, 0, {"feeRate": 10, "add_inputs": False})
+        for bool_add, outputs_array in {True: outputs, False: [{self.nodes[1].getnewaddress(): 1}]}.items():
+            assert_raises_rpc_error(-4, "Fee exceeds maximum configured by user (e.g. -maxtxfee, maxfeerate)",
+                self.nodes[1].walletcreatefundedpsbt, inputs, outputs_array, 0, {"feeRate": 10, "add_inputs": bool_add})
 
+        self.log.info("Test various PSBT operations")
         # partially sign multisig things with node 1
         psbtx = wmulti.walletcreatefundedpsbt(inputs=[{"txid":txid,"vout":p2wsh_pos},{"txid":txid,"vout":p2sh_pos},{"txid":txid,"vout":p2sh_p2wsh_pos}], outputs={self.nodes[1].getnewaddress():29.99}, options={'changeAddress': self.nodes[1].getrawchangeaddress()})['psbt']
         walletprocesspsbt_out = self.nodes[1].walletprocesspsbt(psbtx)
diff --git a/test/functional/wallet_basic.py b/test/functional/wallet_basic.py
index d386d94e0c..40daffd2c2 100755
--- a/test/functional/wallet_basic.py
+++ b/test/functional/wallet_basic.py
@@ -209,6 +209,8 @@ class WalletTest(BitcoinTestFramework):
         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, self.get_vsize(self.nodes[2].gettransaction(txid)['hex']))
 
+        self.log.info("Test sendmany")
+
         # Sendmany 10 BTC
         txid = self.nodes[2].sendmany('', {address: 10}, 0, "", [])
         self.nodes[2].generate(1)
@@ -225,9 +227,9 @@ class WalletTest(BitcoinTestFramework):
         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 with explicit fee (BTC/kB)
+        self.log.info("Test case-insensitive explicit fee rate (sendmany as BTC/kB)")
         # Throw if no conf_target provided
-        assert_raises_rpc_error(-8, "Selected estimate_mode requires a fee rate",
+        assert_raises_rpc_error(-8, "Selected estimate_mode bTc/kB requires a fee rate to be specified in conf_target",
             self.nodes[2].sendmany,
             amounts={ address: 10 },
             estimate_mode='bTc/kB')
@@ -251,9 +253,9 @@ class WalletTest(BitcoinTestFramework):
         node_0_bal += Decimal('10')
         assert_equal(self.nodes[0].getbalance(), node_0_bal)
 
-        # Sendmany with explicit fee (SAT/B)
+        self.log.info("Test case-insensitive explicit fee rate (sendmany as sat/B)")
         # Throw if no conf_target provided
-        assert_raises_rpc_error(-8, "Selected estimate_mode requires a fee rate",
+        assert_raises_rpc_error(-8, "Selected estimate_mode sat/b requires a fee rate to be specified in conf_target",
             self.nodes[2].sendmany,
             amounts={ address: 10 },
             estimate_mode='sat/b')
@@ -279,6 +281,12 @@ class WalletTest(BitcoinTestFramework):
         node_0_bal += Decimal('10')
         assert_equal(self.nodes[0].getbalance(), node_0_bal)
 
+        # Test setting explicit fee rate just below the minimum.
+        for unit, fee_rate in {"BTC/kB": 0.00000999, "sat/B": 0.99999999}.items():
+            self.log.info("Test sendmany raises 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
+            assert_raises_rpc_error(-6, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
+                self.nodes[2].sendmany, amounts={address: 10}, estimate_mode=unit, conf_target=fee_rate)
+
         self.start_node(3, self.nodes[3].extra_args)
         self.connect_nodes(0, 3)
         self.sync_all()
@@ -412,15 +420,14 @@ class WalletTest(BitcoinTestFramework):
             self.nodes[0].generate(1)
             self.sync_all(self.nodes[0:3])
 
-            # send with explicit btc/kb fee
-            self.log.info("test explicit fee (sendtoaddress as btc/kb)")
+            self.log.info("Test case-insensitive explicit fee rate (sendtoaddress as BTC/kB)")
             self.nodes[0].generate(1)
             self.sync_all(self.nodes[0:3])
             prebalance = self.nodes[2].getbalance()
             assert prebalance > 2
             address = self.nodes[1].getnewaddress()
             # Throw if no conf_target provided
-            assert_raises_rpc_error(-8, "Selected estimate_mode requires a fee rate",
+            assert_raises_rpc_error(-8, "Selected estimate_mode BTc/Kb requires a fee rate to be specified in conf_target",
                 self.nodes[2].sendtoaddress,
                 address=address,
                 amount=1.0,
@@ -446,15 +453,15 @@ class WalletTest(BitcoinTestFramework):
             fee = prebalance - postbalance - Decimal('1')
             assert_fee_amount(fee, tx_size, Decimal('0.00002500'))
 
-            # send with explicit sat/b fee
             self.sync_all(self.nodes[0:3])
-            self.log.info("test explicit fee (sendtoaddress as sat/b)")
+
+            self.log.info("Test case-insensitive explicit fee rate (sendtoaddress as sat/B)")
             self.nodes[0].generate(1)
             prebalance = self.nodes[2].getbalance()
             assert prebalance > 2
             address = self.nodes[1].getnewaddress()
             # Throw if no conf_target provided
-            assert_raises_rpc_error(-8, "Selected estimate_mode requires a fee rate",
+            assert_raises_rpc_error(-8, "Selected estimate_mode SAT/b requires a fee rate to be specified in conf_target",
                 self.nodes[2].sendtoaddress,
                 address=address,
                 amount=1.0,
@@ -480,6 +487,12 @@ class WalletTest(BitcoinTestFramework):
             fee = prebalance - postbalance - Decimal('1')
             assert_fee_amount(fee, tx_size, Decimal('0.00002000'))
 
+            # Test setting explicit fee rate just below the minimum.
+            for unit, fee_rate in {"BTC/kB": 0.00000999, "sat/B": 0.99999999}.items():
+                self.log.info("Test sendtoaddress raises 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
+                assert_raises_rpc_error(-6, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
+                    self.nodes[2].sendtoaddress, address=address, amount=1, estimate_mode=unit, conf_target=fee_rate)
+
             # 2. Import address from node2 to node1
             self.nodes[1].importaddress(address_to_import)
 
diff --git a/test/functional/wallet_bumpfee.py b/test/functional/wallet_bumpfee.py
index 9877a9cbd7..88a7778e19 100755
--- a/test/functional/wallet_bumpfee.py
+++ b/test/functional/wallet_bumpfee.py
@@ -17,7 +17,7 @@ from decimal import Decimal
 import io
 
 from test_framework.blocktools import add_witness_commitment, create_block, create_coinbase, send_to_witness
-from test_framework.messages import BIP125_SEQUENCE_NUMBER, CTransaction
+from test_framework.messages import BIP125_SEQUENCE_NUMBER, COIN, CTransaction
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -36,6 +36,8 @@ NORMAL       = 0.00100000
 HIGH         = 0.00500000
 TOO_HIGH     = 1.00000000
 
+BTC_MODE = "BTC/kB"
+SAT_MODE = "sat/B"
 
 class BumpFeeTest(BitcoinTestFramework):
     def set_test_params(self):
@@ -76,10 +78,9 @@ class BumpFeeTest(BitcoinTestFramework):
 
         self.log.info("Running tests")
         dest_address = peer_node.getnewaddress()
-        self.test_invalid_parameters(rbf_node, dest_address)
-        test_simple_bumpfee_succeeds(self, "default", rbf_node, peer_node, dest_address)
-        test_simple_bumpfee_succeeds(self, "fee_rate", rbf_node, peer_node, dest_address)
-        test_feerate_args(self, rbf_node, peer_node, dest_address)
+        for mode in ["default", "fee_rate", BTC_MODE, SAT_MODE]:
+            test_simple_bumpfee_succeeds(self, mode, rbf_node, peer_node, dest_address)
+        self.test_invalid_parameters(rbf_node, peer_node, dest_address)
         test_segwit_bumpfee_succeeds(self, rbf_node, dest_address)
         test_nonrbf_bumpfee_fails(self, peer_node, dest_address)
         test_notmine_bumpfee_fails(self, rbf_node, peer_node, dest_address)
@@ -98,28 +99,56 @@ class BumpFeeTest(BitcoinTestFramework):
         test_small_output_with_feerate_succeeds(self, rbf_node, dest_address)
         test_no_more_inputs_fails(self, rbf_node, dest_address)
 
-    def test_invalid_parameters(self, node, dest_address):
-        txid = spend_one_input(node, dest_address)
-        # invalid estimate mode
-        assert_raises_rpc_error(-8, "Invalid estimate_mode parameter", node.bumpfee, txid, {
-            "estimate_mode": "moo",
-        })
-        assert_raises_rpc_error(-3, "Expected type string", node.bumpfee, txid, {
-            "estimate_mode": 38,
-        })
-        assert_raises_rpc_error(-3, "Expected type string", node.bumpfee, txid, {
-            "estimate_mode": {
-                "foo": "bar",
-            },
-        })
-        assert_raises_rpc_error(-8, "Invalid estimate_mode parameter", node.bumpfee, txid, {
-            "estimate_mode": Decimal("3.141592"),
-        })
-        # confTarget and conf_target
-        assert_raises_rpc_error(-8, "confTarget and conf_target options should not both be set", node.bumpfee, txid, {
-            "confTarget": 123,
-            "conf_target": 456,
-        })
+    def test_invalid_parameters(self, rbf_node, peer_node, dest_address):
+        self.log.info('Test invalid parameters')
+        rbfid = spend_one_input(rbf_node, dest_address)
+        self.sync_mempools((rbf_node, peer_node))
+        assert rbfid in rbf_node.getrawmempool() and rbfid in peer_node.getrawmempool()
+
+        assert_raises_rpc_error(-3, "Unexpected key totalFee", rbf_node.bumpfee, rbfid, {"totalFee": NORMAL})
+        assert_raises_rpc_error(-4, "is too high (cannot be higher than", rbf_node.bumpfee, rbfid, {"fee_rate": TOO_HIGH})
+
+        # For each fee mode, bumping to just above minrelay should fail to increase the total fee enough.
+        for options in [{"fee_rate": INSUFFICIENT}, {"conf_target": INSUFFICIENT, "estimate_mode": BTC_MODE}, {"conf_target": 1, "estimate_mode": SAT_MODE}]:
+            assert_raises_rpc_error(-8, "Insufficient total fee", rbf_node.bumpfee, rbfid, options)
+
+        self.log.info("Test explicit fee rate raises RPC error if estimate_mode is passed without a conf_target")
+        for unit, fee_rate in {"SAT/B": 100, "BTC/KB": NORMAL}.items():
+            assert_raises_rpc_error(-8, "Selected estimate_mode {} requires a fee rate to be specified in conf_target".format(unit),
+                                    rbf_node.bumpfee, rbfid, {"fee_rate": fee_rate, "estimate_mode": unit})
+
+        self.log.info("Test explicit fee rate raises RPC error if both fee_rate and conf_target are passed")
+        error_both = "Cannot specify both conf_target and fee_rate. Please provide either a confirmation " \
+                     "target in blocks for automatic fee estimation, or an explicit fee rate."
+        assert_raises_rpc_error(-8, error_both, rbf_node.bumpfee, rbfid, {"conf_target": NORMAL, "fee_rate": NORMAL})
+
+        self.log.info("Test invalid conf_target settings")
+        assert_raises_rpc_error(-8, "confTarget and conf_target options should not both be set",
+                                rbf_node.bumpfee, rbfid, {"confTarget": 123, "conf_target": 456})
+        for field in ["confTarget", "conf_target"]:
+            assert_raises_rpc_error(-4, "is too high (cannot be higher than -maxtxfee",
+                                    lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": BTC_MODE, "conf_target": 2009}))
+            assert_raises_rpc_error(-4, "is too high (cannot be higher than -maxtxfee",
+                                    lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": SAT_MODE, "conf_target": 2009 * 10000}))
+
+        self.log.info("Test invalid estimate_mode settings")
+        for k, v in {"number": 42, "object": {"foo": "bar"}}.items():
+            assert_raises_rpc_error(-3, "Expected type string for estimate_mode, got {}".format(k),
+                                    lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": v, "fee_rate": NORMAL}))
+        for mode in ["foo", Decimal("3.141592")]:
+            assert_raises_rpc_error(-8, "Invalid estimate_mode parameter",
+                                    lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": mode, "fee_rate": NORMAL}))
+
+        self.log.info("Test invalid fee_rate settings")
+        for mode in ["unset", "economical", "conservative", BTC_MODE, SAT_MODE]:
+            self.log.debug("{}".format(mode))
+            for k, v in {"string": "", "object": {"foo": "bar"}}.items():
+                assert_raises_rpc_error(-3, "Expected type number for fee_rate, got {}".format(k),
+                                        lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": mode, "fee_rate": v}))
+                assert_raises_rpc_error(-3, "Amount out of range",
+                                        lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": mode, "fee_rate": -1}))
+                assert_raises_rpc_error(-8, "Invalid fee_rate 0.00000000 BTC/kB (must be greater than 0)",
+                                        lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": mode, "fee_rate": 0}))
         self.clear_mempool()
 
 
@@ -132,6 +161,13 @@ def test_simple_bumpfee_succeeds(self, mode, rbf_node, peer_node, dest_address):
     if mode == "fee_rate":
         bumped_psbt = rbf_node.psbtbumpfee(rbfid, {"fee_rate": NORMAL})
         bumped_tx = rbf_node.bumpfee(rbfid, {"fee_rate": NORMAL})
+    elif mode == BTC_MODE:
+        bumped_psbt = rbf_node.psbtbumpfee(rbfid, {"conf_target": NORMAL, "estimate_mode": BTC_MODE})
+        bumped_tx = rbf_node.bumpfee(rbfid, {"conf_target": NORMAL, "estimate_mode": BTC_MODE})
+    elif mode == SAT_MODE:
+        sat_fee = NORMAL * COIN / 1000  # convert NORMAL from BTC/kB to sat/B
+        bumped_psbt = rbf_node.psbtbumpfee(rbfid, {"conf_target": sat_fee, "estimate_mode": SAT_MODE})
+        bumped_tx = rbf_node.bumpfee(rbfid, {"conf_target": sat_fee, "estimate_mode": SAT_MODE})
     else:
         bumped_psbt = rbf_node.psbtbumpfee(rbfid)
         bumped_tx = rbf_node.bumpfee(rbfid)
@@ -158,26 +194,6 @@ def test_simple_bumpfee_succeeds(self, mode, rbf_node, peer_node, dest_address):
     self.clear_mempool()
 
 
-def test_feerate_args(self, rbf_node, peer_node, dest_address):
-    self.log.info('Test fee_rate args')
-    rbfid = spend_one_input(rbf_node, dest_address)
-    self.sync_mempools((rbf_node, peer_node))
-    assert rbfid in rbf_node.getrawmempool() and rbfid in peer_node.getrawmempool()
-
-    assert_raises_rpc_error(-8, "conf_target can't be set with fee_rate. Please provide either a confirmation target in blocks for automatic fee estimation, or an explicit fee rate.", rbf_node.bumpfee, rbfid, {"fee_rate": NORMAL, "confTarget": 1})
-
-    assert_raises_rpc_error(-3, "Unexpected key totalFee", rbf_node.bumpfee, rbfid, {"totalFee": NORMAL})
-    assert_raises_rpc_error(-8, "conf_target can't be set with fee_rate. Please provide either a confirmation target in blocks for automatic fee estimation, or an explicit fee rate.", rbf_node.bumpfee, rbfid, {"fee_rate":0.00001, "confTarget": 1})
-
-    # Bumping to just above minrelay should fail to increase total fee enough, at least
-    assert_raises_rpc_error(-8, "Insufficient total fee", rbf_node.bumpfee, rbfid, {"fee_rate": INSUFFICIENT})
-
-    assert_raises_rpc_error(-3, "Amount out of range", rbf_node.bumpfee, rbfid, {"fee_rate": -1})
-
-    assert_raises_rpc_error(-4, "is too high (cannot be higher than", rbf_node.bumpfee, rbfid, {"fee_rate": TOO_HIGH})
-    self.clear_mempool()
-
-
 def test_segwit_bumpfee_succeeds(self, rbf_node, dest_address):
     self.log.info('Test that segwit-sourcing bumpfee works')
     # Create a transaction with segwit output, then create an RBF transaction
diff --git a/test/functional/wallet_send.py b/test/functional/wallet_send.py
index 60ab2d457e..921a726d4b 100755
--- a/test/functional/wallet_send.py
+++ b/test/functional/wallet_send.py
@@ -97,6 +97,8 @@ class WalletSendTest(BitcoinTestFramework):
             except AssertionError:
                 # Provide debug info if the test fails
                 self.log.error("Unexpected successful result:")
+                self.log.error(arg_conf_target)
+                self.log.error(arg_estimate_mode)
                 self.log.error(options)
                 res = from_wallet.send(outputs=outputs, conf_target=arg_conf_target, estimate_mode=arg_estimate_mode, options=options)
                 self.log.error(res)
@@ -224,8 +226,10 @@ class WalletSendTest(BitcoinTestFramework):
         assert_equal(self.nodes[1].decodepsbt(res1["psbt"])["fee"],
                      self.nodes[1].decodepsbt(res2["psbt"])["fee"])
         # but not at the same time
-        self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=1, arg_estimate_mode="economical",
-                       conf_target=1, estimate_mode="economical", add_to_wallet=False, expect_error=(-8,"Use either conf_target and estimate_mode or the options dictionary to control fee rate"))
+        for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=1, arg_estimate_mode="economical",
+                conf_target=1, estimate_mode=mode, add_to_wallet=False,
+                expect_error=(-8, "Use either conf_target and estimate_mode or the options dictionary to control fee rate"))
 
         self.log.info("Create PSBT from watch-only wallet w3, sign with w2...")
         res = self.test_send(from_wallet=w3, to_wallet=w1, amount=1)
@@ -246,19 +250,61 @@ class WalletSendTest(BitcoinTestFramework):
         res = w2.walletprocesspsbt(res["psbt"])
         assert res["complete"]
 
-        self.log.info("Set fee rate...")
+        self.log.info("Test setting explicit fee rate")
+        res1 = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=1, arg_estimate_mode="economical", add_to_wallet=False)
+        res2 = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=1, estimate_mode="economical", add_to_wallet=False)
+        assert_equal(self.nodes[1].decodepsbt(res1["psbt"])["fee"], self.nodes[1].decodepsbt(res2["psbt"])["fee"])
+
+        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0.00007, estimate_mode="btc/kb", add_to_wallet=False)
+        fee = self.nodes[1].decodepsbt(res["psbt"])["fee"]
+        assert_fee_amount(fee, Decimal(len(res["hex"]) / 2), Decimal("0.00007"))
+
         res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=2, estimate_mode="sat/b", add_to_wallet=False)
         fee = self.nodes[1].decodepsbt(res["psbt"])["fee"]
         assert_fee_amount(fee, Decimal(len(res["hex"]) / 2), Decimal("0.00002"))
-        self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=-1, estimate_mode="sat/b",
-                       expect_error=(-3, "Amount out of range"))
-        # Fee rate of 0.1 satoshi per byte should throw an error
-        # TODO: error should use sat/b
-        self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0.1, estimate_mode="sat/b",
-                       expect_error=(-4, "Fee rate (0.00000100 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)"))
-
-        self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0.000001, estimate_mode="BTC/KB",
-                       expect_error=(-4, "Fee rate (0.00000100 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)"))
+
+        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=0.00004531, arg_estimate_mode="btc/kb", add_to_wallet=False)
+        fee = self.nodes[1].decodepsbt(res["psbt"])["fee"]
+        assert_fee_amount(fee, Decimal(len(res["hex"]) / 2), Decimal("0.00004531"))
+
+        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=3, arg_estimate_mode="sat/b", add_to_wallet=False)
+        fee = self.nodes[1].decodepsbt(res["psbt"])["fee"]
+        assert_fee_amount(fee, Decimal(len(res["hex"]) / 2), Decimal("0.00003"))
+
+        # TODO: This test should pass with all modes, e.g. with the next line uncommented, for consistency with the other explicit feerate RPCs.
+        # for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
+        for mode in ["btc/kb", "sat/b"]:
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=-1, estimate_mode=mode,
+                expect_error=(-3, "Amount out of range"))
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0, estimate_mode=mode,
+                expect_error=(-4, "Fee rate (0.00000000 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)"))
+
+        for mode in ["foo", Decimal("3.141592")]:
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0.1, estimate_mode=mode,
+                expect_error=(-8, "Invalid estimate_mode parameter"))
+            # TODO: these 2 equivalent sends with an invalid estimate_mode arg should both fail, but they do not...why?
+            # self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=0.1, arg_estimate_mode=mode,
+            #     expect_error=(-8, "Invalid estimate_mode parameter"))
+            # assert_raises_rpc_error(-8, "Invalid estimate_mode parameter", lambda: w0.send({w1.getnewaddress(): 1}, 0.1, mode))
+
+        # TODO: These tests should pass for consistency with the other explicit feerate RPCs, but they do not.
+        # for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
+        #     self.log.debug("{}".format(mode))
+        #     for k, v in {"string": "", "object": {"foo": "bar"}}.items():
+        #         self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=v, estimate_mode=mode,
+        #             expect_error=(-3, "Expected type number for conf_target, got {}".format(k)))
+
+        # TODO: error should use sat/B instead of BTC/kB if sat/B is selected.
+        # Test setting explicit fee rate just below the minimum.
+        for unit, fee_rate in {"sat/B": 0.99999999, "BTC/kB": 0.00000999}.items():
+            self.log.info("Explicit fee rate raises RPC error 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=fee_rate, estimate_mode=unit,
+                expect_error=(-4, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)"))
+
+        self.log.info("Explicit fee rate raises RPC error if estimate_mode is passed without a conf_target")
+        for unit, fee_rate in {"sat/B": 100, "BTC/kB": 0.001}.items():
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, estimate_mode=unit,
+                expect_error=(-8, "Selected estimate_mode {} requires a fee rate to be specified in conf_target".format(unit)))
 
         # TODO: Return hex if fee rate is below -maxmempool
         # res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0.1, estimate_mode="sat/b", add_to_wallet=False)