diff --git a/src/core_io.h b/src/core_io.h
index 863b0b98c4..bc3ada2ada 100644
--- a/src/core_io.h
+++ b/src/core_io.h
@@ -26,7 +26,15 @@ CScript ParseScript(const std::string& s);
 std::string ScriptToAsmStr(const CScript& script, const bool fAttemptSighashDecode = false);
 [[nodiscard]] bool DecodeHexTx(CMutableTransaction& tx, const std::string& strHexTx);
 [[nodiscard]] bool DecodeHexBlk(CBlock&, const std::string& strHexBlk);
-uint256 ParseHashStr(const std::string&, const std::string& strName);
+/**
+ * Parse a hex string into 256 bits
+ * @param[in] strHex a hex-formatted, 64-character string
+ * @param[out] result the result of the parasing
+ * @returns true if successful, false if not
+ *
+ * @see ParseHashV for an RPC-oriented version of this
+ */
+bool ParseHashStr(const std::string& strHex, uint256& result);
 std::vector<unsigned char> ParseHexUV(const UniValue& v, const std::string& strName);
 bool DecodePSBT(PartiallySignedTransaction& psbt, const std::string& base64_tx, std::string& error);
 int ParseSighashString(const UniValue& sighash);
diff --git a/src/core_read.cpp b/src/core_read.cpp
index a98e9e046a..2c55552815 100644
--- a/src/core_read.cpp
+++ b/src/core_read.cpp
@@ -142,14 +142,13 @@ bool DecodePSBT(PartiallySignedTransaction& psbt, const std::string& base64_tx,
     return true;
 }
 
-uint256 ParseHashStr(const std::string& strHex, const std::string& strName)
+bool ParseHashStr(const std::string& strHex, uint256& result)
 {
-    if (!IsHex(strHex)) // Note: IsHex("") is false
-        throw std::runtime_error(strName + " must be hexadecimal string (not '" + strHex + "')");
+    if ((strHex.size() != 64) || !IsHex(strHex))
+        return false;
 
-    uint256 result;
     result.SetHex(strHex);
-    return result;
+    return true;
 }
 
 std::vector<unsigned char> ParseHexUV(const UniValue& v, const std::string& strName)
diff --git a/src/dash-tx.cpp b/src/dash-tx.cpp
index ed30ace65e..f5de915240 100644
--- a/src/dash-tx.cpp
+++ b/src/dash-tx.cpp
@@ -222,10 +222,10 @@ static void MutateTxAddInput(CMutableTransaction& tx, const std::string& strInpu
         throw std::runtime_error("TX input missing separator");
 
     // extract and validate TXID
-    std::string strTxid = vStrInputParts[0];
-    if ((strTxid.size() != 64) || !IsHex(strTxid))
+    uint256 txid;
+    if (!ParseHashStr(vStrInputParts[0], txid)) {
         throw std::runtime_error("invalid TX input txid");
-    uint256 txid(uint256S(strTxid));
+    }
 
     static const unsigned int minTxOutSz = 9;
     static const unsigned int maxVout = MaxBlockSize() / minTxOutSz;
@@ -547,7 +547,10 @@ static void MutateTxSign(CMutableTransaction& tx, const std::string& flagStr)
             if (!prevOut.checkObject(types))
                 throw std::runtime_error("prevtxs internal object typecheck fail");
 
-            uint256 txid = ParseHashStr(prevOut["txid"].get_str(), "txid");
+            uint256 txid;
+            if (!ParseHashStr(prevOut["txid"].get_str(), txid)) {
+                throw std::runtime_error("txid must be hexadecimal string (not '" + prevOut["txid"].get_str() + "')");
+            }
 
             const int nOut = prevOut["vout"].get_int();
             if (nOut < 0)
diff --git a/src/rest.cpp b/src/rest.cpp
index 946ebfde11..c0f46525c4 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -101,15 +101,6 @@ static std::string AvailableDataFormatsString()
     return formats;
 }
 
-static bool ParseHashStr(const std::string& strReq, uint256& v)
-{
-    if (!IsHex(strReq) || (strReq.size() != 64))
-        return false;
-
-    v.SetHex(strReq);
-    return true;
-}
-
 static bool CheckWarmup(HTTPRequest* req)
 {
     std::string statusmessage;
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index bc685f421f..759c370601 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -261,7 +261,7 @@ static UniValue prioritisetransaction(const JSONRPCRequest& request)
 
     LOCK(cs_main);
 
-    uint256 hash = ParseHashStr(request.params[0].get_str(), "txid");
+    uint256 hash = ParseHashV(request.params[0].get_str(), "txid");
     CAmount nAmount = request.params[1].get_int64();
 
     mempool.PrioritiseTransaction(hash, nAmount);
diff --git a/src/test/blockfilter_tests.cpp b/src/test/blockfilter_tests.cpp
index 6f93bc76e2..f888593989 100644
--- a/src/test/blockfilter_tests.cpp
+++ b/src/test/blockfilter_tests.cpp
@@ -114,7 +114,8 @@ BOOST_AUTO_TEST_CASE(blockfilters_json_test)
 
         unsigned int pos = 0;
         /*int block_height =*/ test[pos++].get_int();
-        /*uint256 block_hash =*/ ParseHashStr(test[pos++].get_str(), "block_hash");
+        uint256 block_hash;
+        BOOST_CHECK(ParseHashStr(test[pos++].get_str(), block_hash));
 
         CBlock block;
         BOOST_REQUIRE(DecodeHexBlk(block, test[pos++].get_str()));
@@ -129,9 +130,11 @@ BOOST_AUTO_TEST_CASE(blockfilters_json_test)
             tx_undo.vprevout.emplace_back(txout, 0, false);
         }
 
-        uint256 prev_filter_header_basic = ParseHashStr(test[pos++].get_str(), "prev_filter_header_basic");
+        uint256 prev_filter_header_basic;
+        BOOST_CHECK(ParseHashStr(test[pos++].get_str(), prev_filter_header_basic));
         std::vector<unsigned char> filter_basic = ParseHex(test[pos++].get_str());
-        uint256 filter_header_basic = ParseHashStr(test[pos++].get_str(), "filter_header_basic");
+        uint256 filter_header_basic;
+        BOOST_CHECK(ParseHashStr(test[pos++].get_str(), filter_header_basic));
 
         BlockFilter computed_filter_basic(BlockFilterType::BASIC_FILTER, block, block_undo);
         BOOST_CHECK(computed_filter_basic.GetFilter().GetEncoded() == filter_basic);
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 337e491937..473a3edf17 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -3945,6 +3945,8 @@ UniValue signrawtransactionwithwallet(const JSONRPCRequest& request)
     // Sign the transaction
     LOCK2(cs_main, mempool.cs);
     LOCK(pwallet->cs_wallet);
+    EnsureWalletIsUnlocked(pwallet);
+
     return SignTransaction(mtx, request.params[1], pwallet, false, request.params[2]);
 }
 
diff --git a/test/functional/README.md b/test/functional/README.md
index 6f82314c09..218439ab2c 100644
--- a/test/functional/README.md
+++ b/test/functional/README.md
@@ -64,6 +64,11 @@ don't have test cases for.
 - When calling RPCs with lots of arguments, consider using named keyword
   arguments instead of positional arguments to make the intent of the call
   clear to readers.
+- Many of the core test framework classes such as `CBlock` and `CTransaction`
+  don't allow new attributes to be added to their objects at runtime like
+  typical Python objects allow. This helps prevent unpredictable side effects
+  from typographical errors or usage of the objects outside of their intended
+  purpose.
 
 #### RPC and P2P definitions
 
@@ -76,7 +81,7 @@ P2P messages. These can be found in the following source files:
 
 #### Using the P2P interface
 
-- `mininode.py` contains all the definitions for objects that pass
+- `messages.py` contains all the definitions for objects that pass
 over the network (`CBlock`, `CTransaction`, etc, along with the network-level
 wrappers for them, `msg_block`, `msg_tx`, etc).
 
diff --git a/test/functional/mining_prioritisetransaction.py b/test/functional/mining_prioritisetransaction.py
index 28709c084a..79e0066cc2 100755
--- a/test/functional/mining_prioritisetransaction.py
+++ b/test/functional/mining_prioritisetransaction.py
@@ -23,7 +23,8 @@ class PrioritiseTransactionTest(BitcoinTestFramework):
         assert_raises_rpc_error(-1, "prioritisetransaction", self.nodes[0].prioritisetransaction, '', 0, 0)
 
         # Test `prioritisetransaction` invalid `txid`
-        assert_raises_rpc_error(-1, "txid must be hexadecimal string", self.nodes[0].prioritisetransaction, txid='foo', fee_delta=0)
+        assert_raises_rpc_error(-8, "txid must be hexadecimal string", self.nodes[0].prioritisetransaction, txid='foo', fee_delta=0)
+        assert_raises_rpc_error(-8, "txid must be hexadecimal string (not 'Zd1d4e24ed99057e84c3f80fd8fbec79ed9e1acee37da269356ecea000000000')", self.nodes[0].prioritisetransaction, txid='Zd1d4e24ed99057e84c3f80fd8fbec79ed9e1acee37da269356ecea000000000', fee_delta=0)
 
         txid = '1d1d4e24ed99057e84c3f80fd8fbec79ed9e1acee37da269356ecea000000000'
 
diff --git a/test/functional/rpc_signrawtransaction.py b/test/functional/rpc_signrawtransaction.py
index d316437678..7f473ff26b 100755
--- a/test/functional/rpc_signrawtransaction.py
+++ b/test/functional/rpc_signrawtransaction.py
@@ -46,6 +46,14 @@ class SignRawTransactionsTest(BitcoinTestFramework):
         rawTxSigned2 = self.nodes[0].signrawtransaction(rawTx, inputs, privKeys)
         assert_equal(rawTxSigned, rawTxSigned2)
 
+    def test_with_lock_outputs(self):
+        """Test correct error reporting when trying to sign a locked output"""
+        self.nodes[0].encryptwallet("password")
+
+        rawTx = '020000000156b958f78e3f24e0b2f4e4db1255426b0902027cb37e3ddadb52e37c3557dddb0000000000ffffffff01c0a6b929010000001600149a2ee8c77140a053f36018ac8124a6ececc1668a00000000'
+
+        assert_raises_rpc_error(-13, "Please enter the wallet passphrase with walletpassphrase first", self.nodes[0].signrawtransactionwithwallet, rawTx)
+
     def script_verification_error_test(self):
         """Create and sign a raw transaction with valid (vin 0), invalid (vin 1) and one missing (vin 2) input script.
 
@@ -117,6 +125,7 @@ class SignRawTransactionsTest(BitcoinTestFramework):
     def run_test(self):
         self.successful_signing_test()
         self.script_verification_error_test()
+        self.test_with_lock_outputs()
 
 
 if __name__ == '__main__':
diff --git a/test/functional/test_framework/messages.py b/test/functional/test_framework/messages.py
index e07a5318c2..1b49309446 100755
--- a/test/functional/test_framework/messages.py
+++ b/test/functional/test_framework/messages.py
@@ -10,7 +10,12 @@ CBlock, CTransaction, CBlockHeader, CTxIn, CTxOut, etc....:
     bitcoin/primitives
 msg_block, msg_tx, msg_headers, etc.:
     data structures that represent network messages
-ser_*, deser_*: functions that handle serialization/deserialization."""
+
+ser_*, deser_*: functions that handle serialization/deserialization.
+
+Classes use __slots__ to ensure extraneous attributes aren't accidentally added
+by tests, compromising their intended effect.
+"""
 from codecs import encode
 import copy
 from collections import namedtuple
@@ -215,7 +220,9 @@ def ToHex(obj):
 
 # Objects that map to dashd objects, which can be serialized/deserialized
 
-class CService():
+class CService:
+    __slots__ = ("ip", "port")
+
     def __init__(self):
         self.ip = ""
         self.port = 0
@@ -234,7 +241,7 @@ class CService():
         return "CService(ip=%s port=%i)" % (self.ip, self.port)
 
 
-class CAddress():
+class CAddress:
     __slots__ = ("net", "ip", "nServices", "port", "time")
 
     # see https://github.com/bitcoin/bips/blob/master/bip-0155.mediawiki
@@ -313,7 +320,9 @@ class CAddress():
                 % (self.nServices, self.ADDRV2_NET_NAME[self.net], self.ip, self.port))
 
 
-class CInv():
+class CInv:
+    __slots__ = ("hash", "type")
+
     typemap = {
         0: "Error",
         1: "TX",
@@ -340,7 +349,9 @@ class CInv():
                % (self.typemap.get(self.type, "%d" % self.type), self.hash)
 
 
-class CBlockLocator():
+class CBlockLocator:
+    __slots__ = ("nVersion", "vHave")
+
     def __init__(self):
         self.nVersion = MY_VERSION
         self.vHave = []
@@ -360,7 +371,9 @@ class CBlockLocator():
                % (self.nVersion, repr(self.vHave))
 
 
-class COutPoint():
+class COutPoint:
+    __slots__ = ("hash", "n")
+
     def __init__(self, hash=0, n=0xFFFFFFFF):
         self.hash = hash
         self.n = n
@@ -379,7 +392,9 @@ class COutPoint():
         return "COutPoint(hash=%064x n=%i)" % (self.hash, self.n)
 
 
-class CTxIn():
+class CTxIn:
+    __slots__ = ("nSequence", "prevout", "scriptSig")
+
     def __init__(self, outpoint=None, scriptSig=b"", nSequence=0):
         if outpoint is None:
             self.prevout = COutPoint()
@@ -407,7 +422,9 @@ class CTxIn():
                   self.nSequence)
 
 
-class CTxOut():
+class CTxOut:
+    __slots__ = ("nValue", "scriptPubKey")
+
     def __init__(self, nValue=0, scriptPubKey=b""):
         self.nValue = nValue
         self.scriptPubKey = scriptPubKey
@@ -428,7 +445,10 @@ class CTxOut():
                   bytes_to_hex_str(self.scriptPubKey))
 
 
-class CTransaction():
+class CTransaction:
+    __slots__ = ("hash", "nLockTime", "nVersion", "sha256", "vin", "vout",
+                 "nType", "vExtraPayload")
+
     def __init__(self, tx=None):
         if tx is None:
             self.nVersion = 1
@@ -494,7 +514,10 @@ class CTransaction():
                % (self.nVersion, repr(self.vin), repr(self.vout), self.nLockTime)
 
 
-class CBlockHeader():
+class CBlockHeader:
+    __slots__ = ("hash", "hashMerkleRoot", "hashPrevBlock", "nBits", "nNonce",
+                 "nTime", "nVersion", "sha256")
+
     def __init__(self, header=None):
         if header is None:
             self.set_null()
@@ -563,6 +586,8 @@ class CBlockHeader():
 
 
 class CBlock(CBlockHeader):
+    __slots__ = ("vtx",)
+
     def __init__(self, header=None):
         super(CBlock, self).__init__(header)
         self.vtx = []
@@ -619,7 +644,9 @@ class CBlock(CBlockHeader):
                % (self.nVersion, self.hashPrevBlock, self.hashMerkleRoot,
                   time.ctime(self.nTime), self.nBits, self.nNonce, repr(self.vtx))
 
-class PrefilledTransaction():
+class PrefilledTransaction:
+    __slots__ = ("index", "tx")
+
     def __init__(self, index=0, tx = None):
         self.index = index
         self.tx = tx
@@ -638,8 +665,12 @@ class PrefilledTransaction():
     def __repr__(self):
         return "PrefilledTransaction(index=%d, tx=%s)" % (self.index, repr(self.tx))
 
+
 # This is what we send on the wire, in a cmpctblock message.
-class P2PHeaderAndShortIDs():
+class P2PHeaderAndShortIDs:
+    __slots__ = ("header", "nonce", "prefilled_txn", "prefilled_txn_length",
+                 "shortids", "shortids_length")
+
     def __init__(self):
         self.header = CBlockHeader()
         self.nonce = 0
@@ -680,9 +711,12 @@ def calculate_shortid(k0, k1, tx_hash):
     expected_shortid &= 0x0000ffffffffffff
     return expected_shortid
 
+
 # This version gets rid of the array lengths, and reinterprets the differential
 # encoding into indices that can be used for lookup.
-class HeaderAndShortIDs():
+class HeaderAndShortIDs:
+    __slots__ = ("header", "nonce", "prefilled_txn", "shortids")
+
     def __init__(self, p2pheaders_and_shortids = None):
         self.header = CBlockHeader()
         self.nonce = 0
@@ -734,7 +768,8 @@ class HeaderAndShortIDs():
         return "HeaderAndShortIDs(header=%s, nonce=%d, shortids=%s, prefilledtxn=%s" % (repr(self.header), self.nonce, repr(self.shortids), repr(self.prefilled_txn))
 
 
-class BlockTransactionsRequest():
+class BlockTransactionsRequest:
+    __slots__ = ("blockhash", "indexes")
 
     def __init__(self, blockhash=0, indexes = None):
         self.blockhash = blockhash
@@ -774,7 +809,8 @@ class BlockTransactionsRequest():
         return "BlockTransactionsRequest(hash=%064x indexes=%s)" % (self.blockhash, repr(self.indexes))
 
 
-class BlockTransactions():
+class BlockTransactions:
+    __slots__ = ("blockhash", "transactions")
 
     def __init__(self, blockhash=0, transactions = None):
         self.blockhash = blockhash
@@ -794,7 +830,9 @@ class BlockTransactions():
         return "BlockTransactions(hash=%064x transactions=%s)" % (self.blockhash, repr(self.transactions))
 
 
-class CPartialMerkleTree():
+class CPartialMerkleTree:
+    __slots__ = ("fBad", "nTransactions", "vBits", "vHash")
+
     def __init__(self):
         self.nTransactions = 0
         self.vBits = []
@@ -817,7 +855,9 @@ class CPartialMerkleTree():
         return "CPartialMerkleTree(nTransactions=%d vBits.size=%d vHash.size=%d)" % (self.nTransactions, len(self.vBits), len(self.vHash))
 
 
-class CMerkleBlock():
+class CMerkleBlock:
+    __slots__ = ("header", "txn")
+
     def __init__(self, header=CBlockHeader(), txn=CPartialMerkleTree()):
         self.header = header
         self.txn = txn
@@ -836,7 +876,9 @@ class CMerkleBlock():
         return "CMerkleBlock(header=%s txn=%s)" % (repr(self.header), repr(self.txn))
 
 
-class CCbTx():
+class CCbTx:
+    __slots__ = ("version", "height", "merkleRootMNList", "merkleRootQuorums")
+
     def __init__(self, version=None, height=None, merkleRootMNList=None, merkleRootQuorums=None):
         self.set_null()
         if version is not None:
@@ -870,7 +912,9 @@ class CCbTx():
         return r
 
 
-class CSimplifiedMNListEntry():
+class CSimplifiedMNListEntry:
+    __slots__ = ("proRegTxHash", "confirmedHash", "service", "pubKeyOperator", "keyIDVoting", "isValid")
+
     def __init__(self):
         self.set_null()
 
@@ -902,6 +946,9 @@ class CSimplifiedMNListEntry():
 
 
 class CFinalCommitment:
+    __slots__ = ("nVersion", "llmqType", "quorumHash", "signers", "validMembers", "quorumPublicKey",
+                 "quorumVvecHash", "quorumSig", "membersSig")
+
     def __init__(self):
         self.set_null()
 
@@ -942,6 +989,9 @@ class CFinalCommitment:
 
 
 class CGovernanceObject:
+    __slots__ = ("nHashParent", "nRevision", "nTime", "nCollateralHash", "vchData", "nObjectType",
+                 "masternodeOutpoint", "vchSig")
+
     def __init__(self):
         self.nHashParent = 0
         self.nRevision = 0
@@ -982,6 +1032,8 @@ class CGovernanceObject:
 
 
 class CGovernanceVote:
+    __slots__ = ("masternodeOutpoint", "nParentHash", "nVoteOutcome", "nVoteSignal", "nTime", "vchSig")
+
     def __init__(self):
         self.masternodeOutpoint = COutPoint()
         self.nParentHash = 0
@@ -1013,6 +1065,8 @@ class CGovernanceVote:
 
 
 class CRecoveredSig:
+    __slots__ = ("llmqType", "quorumHash", "id", "msgHash", "sig")
+
     def __init__(self):
         self.llmqType = 0
         self.quorumHash = 0
@@ -1038,6 +1092,8 @@ class CRecoveredSig:
 
 
 class CSigShare:
+    __slots__ = ("llmqType", "quorumHash", "quorumMember", "id", "msgHash", "sigShare")
+
     def __init__(self):
         self.llmqType = 0
         self.quorumHash = 0
@@ -1066,6 +1122,8 @@ class CSigShare:
 
 
 class CBLSPublicKey:
+    __slots__ = ("data")
+
     def __init__(self):
         self.data = b'\\x0' * 48
 
@@ -1079,6 +1137,8 @@ class CBLSPublicKey:
 
 
 class CBLSIESEncryptedSecretKey:
+    __slots__ = ("ephemeral_pubKey", "iv", "data")
+
     def __init__(self):
         self.ephemeral_pubKey = b'\\x0' * 48
         self.iv = b'\\x0' * 32
@@ -1100,7 +1160,9 @@ class CBLSIESEncryptedSecretKey:
 
 
 # Objects that correspond to messages on the wire
-class msg_version():
+class msg_version:
+    __slots__ = ("addrFrom", "addrTo", "nNonce", "nRelay", "nServices",
+                 "nStartingHeight", "nTime", "nVersion", "strSubVer")
     command = b"version"
 
     def __init__(self):
@@ -1157,7 +1219,8 @@ class msg_version():
                   self.strSubVer, self.nStartingHeight, self.nRelay)
 
 
-class msg_verack():
+class msg_verack:
+    __slots__ = ()
     command = b"verack"
 
     def __init__(self):
@@ -1173,7 +1236,8 @@ class msg_verack():
         return "msg_verack()"
 
 
-class msg_addr():
+class msg_addr:
+    __slots__ = ("addrs",)
     command = b"addr"
 
     def __init__(self):
@@ -1189,8 +1253,8 @@ class msg_addr():
         return "msg_addr(addrs=%s)" % (repr(self.addrs))
 
 
-class msg_addrv2():
-    # __slots__ = ("addrs",)
+class msg_addrv2:
+    __slots__ = ("addrs",)
     # msgtype = b"addrv2"
     command = b"addrv2"
 
@@ -1207,8 +1271,8 @@ class msg_addrv2():
         return "msg_addrv2(addrs=%s)" % (repr(self.addrs))
 
 
-class msg_sendaddrv2():
-    # __slots__ = ()
+class msg_sendaddrv2:
+    __slots__ = ()
     # msgtype = b"sendaddrv2"
     command = b"sendaddrv2"
 
@@ -1225,7 +1289,8 @@ class msg_sendaddrv2():
         return "msg_sendaddrv2()"
 
 
-class msg_inv():
+class msg_inv:
+    __slots__ = ("inv",)
     command = b"inv"
 
     def __init__(self, inv=None):
@@ -1244,7 +1309,8 @@ class msg_inv():
         return "msg_inv(inv=%s)" % (repr(self.inv))
 
 
-class msg_getdata():
+class msg_getdata:
+    __slots__ = ("inv",)
     command = b"getdata"
 
     def __init__(self, inv=None):
@@ -1260,7 +1326,8 @@ class msg_getdata():
         return "msg_getdata(inv=%s)" % (repr(self.inv))
 
 
-class msg_getblocks():
+class msg_getblocks:
+    __slots__ = ("locator", "hashstop")
     command = b"getblocks"
 
     def __init__(self):
@@ -1283,7 +1350,8 @@ class msg_getblocks():
                % (repr(self.locator), self.hashstop)
 
 
-class msg_tx():
+class msg_tx:
+    __slots__ = ("tx",)
     command = b"tx"
 
     def __init__(self, tx=CTransaction()):
@@ -1299,7 +1367,8 @@ class msg_tx():
         return "msg_tx(tx=%s)" % (repr(self.tx))
 
 
-class msg_block():
+class msg_block:
+    __slots__ = ("block",)
     command = b"block"
 
     def __init__(self, block=None):
@@ -1319,7 +1388,9 @@ class msg_block():
 
 # for cases where a user needs tighter control over what is sent over the wire
 # note that the user must supply the name of the command, and the data
-class msg_generic():
+class msg_generic:
+    __slots__ = ("command", "data")
+
     def __init__(self, command, data=None):
         self.command = command
         self.data = data
@@ -1330,7 +1401,9 @@ class msg_generic():
     def __repr__(self):
         return "msg_generic()"
 
-class msg_getaddr():
+
+class msg_getaddr:
+    __slots__ = ()
     command = b"getaddr"
 
     def __init__(self):
@@ -1346,7 +1419,8 @@ class msg_getaddr():
         return "msg_getaddr()"
 
 
-class msg_ping():
+class msg_ping:
+    __slots__ = ("nonce",)
     command = b"ping"
 
     def __init__(self, nonce=0):
@@ -1364,7 +1438,8 @@ class msg_ping():
         return "msg_ping(nonce=%08x)" % self.nonce
 
 
-class msg_pong():
+class msg_pong:
+    __slots__ = ("nonce",)
     command = b"pong"
 
     def __init__(self, nonce=0):
@@ -1382,7 +1457,8 @@ class msg_pong():
         return "msg_pong(nonce=%08x)" % self.nonce
 
 
-class msg_mempool():
+class msg_mempool:
+    __slots__ = ()
     command = b"mempool"
 
     def __init__(self):
@@ -1414,7 +1490,8 @@ class msg_notfound:
         return "msg_notfound(vec=%s)" % (repr(self.vec))
 
 
-class msg_sendheaders():
+class msg_sendheaders:
+    __slots__ = ()
     command = b"sendheaders"
 
     def __init__(self):
@@ -1434,7 +1511,8 @@ class msg_sendheaders():
 # number of entries
 # vector of hashes
 # hash_stop (hash of last desired block header, 0 to get as many as possible)
-class msg_getheaders():
+class msg_getheaders:
+    __slots__ = ("hashstop", "locator",)
     command = b"getheaders"
 
     def __init__(self):
@@ -1459,7 +1537,8 @@ class msg_getheaders():
 
 # headers message has
 # <count> <vector of block headers>
-class msg_headers():
+class msg_headers:
+    __slots__ = ("headers",)
     command = b"headers"
 
     def __init__(self, headers=None):
@@ -1479,7 +1558,8 @@ class msg_headers():
         return "msg_headers(headers=%s)" % repr(self.headers)
 
 
-class msg_reject():
+class msg_reject:
+    __slots__ = ("code", "data", "message", "reason")
     command = b"reject"
     REJECT_MALFORMED = 1
 
@@ -1511,7 +1591,8 @@ class msg_reject():
                % (self.message, self.code, self.reason, self.data)
 
 
-class msg_sendcmpct():
+class msg_sendcmpct:
+    __slots__ = ("announce", "version")
     command = b"sendcmpct"
 
     def __init__(self):
@@ -1531,7 +1612,9 @@ class msg_sendcmpct():
     def __repr__(self):
         return "msg_sendcmpct(announce=%s, version=%lu)" % (self.announce, self.version)
 
-class msg_cmpctblock():
+
+class msg_cmpctblock:
+    __slots__ = ("header_and_shortids",)
     command = b"cmpctblock"
 
     def __init__(self, header_and_shortids = None):
@@ -1549,7 +1632,9 @@ class msg_cmpctblock():
     def __repr__(self):
         return "msg_cmpctblock(HeaderAndShortIDs=%s)" % repr(self.header_and_shortids)
 
-class msg_getblocktxn():
+
+class msg_getblocktxn:
+    __slots__ = ("block_txn_request",)
     command = b"getblocktxn"
 
     def __init__(self):
@@ -1567,7 +1652,9 @@ class msg_getblocktxn():
     def __repr__(self):
         return "msg_getblocktxn(block_txn_request=%s)" % (repr(self.block_txn_request))
 
-class msg_blocktxn():
+
+class msg_blocktxn:
+    __slots__ = ("block_transactions",)
     command = b"blocktxn"
 
     def __init__(self):
@@ -1584,7 +1671,9 @@ class msg_blocktxn():
     def __repr__(self):
         return "msg_blocktxn(block_transactions=%s)" % (repr(self.block_transactions))
 
-class msg_getmnlistd():
+
+class msg_getmnlistd:
+    __slots__ = ("baseBlockHash", "blockHash",)
     command = b"getmnlistd"
 
     def __init__(self, baseBlockHash=0, blockHash=0):
@@ -1606,7 +1695,8 @@ class msg_getmnlistd():
 
 QuorumId = namedtuple('QuorumId', ['llmqType', 'quorumHash'])
 
-class msg_mnlistdiff():
+class msg_mnlistdiff:
+    __slots__ = ("baseBlockHash", "blockHash", "merkleProof", "cbTx", "deletedMNs", "mnList", "deletedQuorums", "newQuorums",)
     command = b"mnlistdiff"
 
     def __init__(self):
@@ -1648,7 +1738,8 @@ class msg_mnlistdiff():
         return "msg_mnlistdiff(baseBlockHash=%064x, blockHash=%064x)" % (self.baseBlockHash, self.blockHash)
 
 
-class msg_clsig():
+class msg_clsig:
+    __slots__ = ("height", "blockHash", "sig",)
     command = b"clsig"
 
     def __init__(self, height=0, blockHash=0, sig=b'\\x0' * 96):
@@ -1672,7 +1763,8 @@ class msg_clsig():
         return "msg_clsig(height=%d, blockHash=%064x)" % (self.height, self.blockHash)
 
 
-class msg_islock():
+class msg_islock:
+    __slots__ = ("inputs", "txid", "sig",)
     command = b"islock"
 
     def __init__(self, inputs=[], txid=0, sig=b'\\x0' * 96):
@@ -1696,7 +1788,8 @@ class msg_islock():
         return "msg_islock(inputs=%s, txid=%064x)" % (repr(self.inputs), self.txid)
 
 
-class msg_qsigshare():
+class msg_qsigshare:
+    __slots__ = ("sig_shares",)
     command = b"qsigshare"
 
     def __init__(self, sig_shares=[]):
@@ -1714,7 +1807,8 @@ class msg_qsigshare():
         return "msg_qsigshare(sigShares=%d)" % (len(self.sig_shares))
 
 
-class msg_qwatch():
+class msg_qwatch:
+    __slots__ = ()
     command = b"qwatch"
 
     def __init__(self):
@@ -1730,7 +1824,8 @@ class msg_qwatch():
         return "msg_qwatch()"
 
 
-class msg_qgetdata():
+class msg_qgetdata:
+    __slots__ = ("quorum_hash", "quorum_type", "data_mask", "protx_hash")
     command = b"qgetdata"
 
     def __init__(self, quorum_hash=0, quorum_type=-1, data_mask=0, protx_hash=0):
@@ -1761,7 +1856,8 @@ class msg_qgetdata():
                                                                                 self.protx_hash)
 
 
-class msg_qdata():
+class msg_qdata:
+    __slots__ = ("quorum_hash", "quorum_type", "data_mask", "protx_hash", "error", "quorum_vvec", "enc_contributions",)
     command = b"qdata"
 
     def __init__(self):
diff --git a/test/functional/test_framework/script.py b/test/functional/test_framework/script.py
index 4dfb787323..df7c7e397f 100644
--- a/test/functional/test_framework/script.py
+++ b/test/functional/test_framework/script.py
@@ -25,7 +25,7 @@ def hash160(s):
 _opcode_instances = []
 class CScriptOp(int):
     """A single script opcode"""
-    __slots__ = []
+    __slots__ = ()
 
     @staticmethod
     def encode_op_pushdata(d):
@@ -362,8 +362,11 @@ class CScriptTruncatedPushDataError(CScriptInvalidError):
         self.data = data
         super(CScriptTruncatedPushDataError, self).__init__(msg)
 
+
 # This is used, eg, for blockchain heights in coinbase scripts (bip34)
-class CScriptNum():
+class CScriptNum:
+    __slots__ = ("value",)
+
     def __init__(self, d=0):
         self.value = d
 
@@ -394,6 +397,8 @@ class CScript(bytes):
 
     iter(script) however does iterate by opcode.
     """
+    __slots__ = ()
+
     @classmethod
     def __coerce_instance(cls, other):
         # Coerce other into bytes
diff --git a/test/util/data/bitcoin-util-test.json b/test/util/data/bitcoin-util-test.json
index 86e52e58ca..126b28b189 100644
--- a/test/util/data/bitcoin-util-test.json
+++ b/test/util/data/bitcoin-util-test.json
@@ -102,6 +102,30 @@
     "error_txt": "error: Invalid TX locktime requested",
     "description": "Tests the check for invalid locktime value"
   },
+  { "exec": "./dash-tx",
+    "args":
+    ["-create",
+      "in=Z897de6bd6027a475eadd57019d4e6872c396d0716c4875a5f1a6fcfdf385c1f:0"],
+    "return_code": 1,
+    "error_txt": "error: invalid TX input txid",
+    "description": "Tests the check for an invalid txid invalid hex"
+  },
+  { "exec": "./dash-tx",
+    "args":
+    ["-create",
+      "in=5897de6bd6:0"],
+    "return_code": 1,
+    "error_txt": "error: invalid TX input txid",
+    "description": "Tests the check for an invalid txid valid hex but too short"
+  },
+  { "exec": "./dash-tx",
+    "args":
+    ["-create",
+      "in=5897de6bd6027a475eadd57019d4e6872c396d0716c4875a5f1a6fcfdf385c1f12:0"],
+    "return_code": 1,
+    "error_txt": "error: invalid TX input txid",
+    "description": "Tests the check for an invalid txid valid hex but too long"
+  },
   { "exec": "./dash-tx",
     "args":
     ["-create",
@@ -251,6 +275,42 @@
     "error_txt": "error: prevtxs internal object typecheck fail",
     "description": "Tests the check for invalid vout index in prevtxs for sign"
   },
+  { "exec": "./dash-tx",
+    "args":
+    ["-create",
+      "in=4d49a71ec9da436f71ec4ee231d04f292a29cd316f598bb7068feccabdc59485:0",
+      "set=privatekeys:[\"7qYrzJZWqnyCWMYswFcqaRJypGdVceudXPSxmZKsngN7fyo7aAV\"]",
+      "set=prevtxs:[{\"txid\":\"Zd49a71ec9da436f71ec4ee231d04f292a29cd316f598bb7068feccabdc59412\",\"vout\":0,\"scriptPubKey\":\"76a91491b24bf9f5288532960ac687abb035127b1d28a588ac\"}]",
+      "sign=ALL",
+      "outaddr=0.001:XijDvbYpPmznwgpWD3DkdYNfGmRP2KoVSk"],
+    "return_code": 1,
+    "error_txt": "error: txid must be hexadecimal string (not 'Zd49a71ec9da436f71ec4ee231d04f292a29cd316f598bb7068feccabdc59412')",
+    "description": "Tests the check for invalid txid due to invalid hex"
+  },
+  { "exec": "./dash-tx",
+    "args":
+    ["-create",
+      "in=4d49a71ec9da436f71ec4ee231d04f292a29cd316f598bb7068feccabdc59485:0",
+      "set=privatekeys:[\"7qYrzJZWqnyCWMYswFcqaRJypGdVceudXPSxmZKsngN7fyo7aAV\"]",
+      "set=prevtxs:[{\"txid\":\"4d49a71ec9da436f71ec4ee231d04f292a29cd316f598bb7068feccabdc594\",\"vout\":0,\"scriptPubKey\":\"76a91491b24bf9f5288532960ac687abb035127b1d28a588ac\"}]",
+      "sign=ALL",
+      "outaddr=0.001:XijDvbYpPmznwgpWD3DkdYNfGmRP2KoVSk"],
+    "return_code": 1,
+    "error_txt": "error: txid must be hexadecimal string (not '4d49a71ec9da436f71ec4ee231d04f292a29cd316f598bb7068feccabdc594')",
+    "description": "Tests the check for invalid txid valid hex, but too short"
+  },
+  { "exec": "./dash-tx",
+    "args":
+    ["-create",
+      "in=4d49a71ec9da436f71ec4ee231d04f292a29cd316f598bb7068feccabdc59485:0",
+      "set=privatekeys:[\"7qYrzJZWqnyCWMYswFcqaRJypGdVceudXPSxmZKsngN7fyo7aAV\"]",
+      "set=prevtxs:[{\"txid\":\"4d49a71ec9da436f71ec4ee231d04f292a29cd316f598bb7068feccabdc5948512\",\"vout\":0,\"scriptPubKey\":\"76a91491b24bf9f5288532960ac687abb035127b1d28a588ac\"}]",
+      "sign=ALL",
+      "outaddr=0.001:XijDvbYpPmznwgpWD3DkdYNfGmRP2KoVSk"],
+    "return_code": 1,
+    "error_txt": "error: txid must be hexadecimal string (not '4d49a71ec9da436f71ec4ee231d04f292a29cd316f598bb7068feccabdc5948512')",
+    "description": "Tests the check for invalid txid valid hex, but too long"
+  },
   { "exec": "./dash-tx",
     "args":
     ["-create", "outpubkey=0:02a5613bd857b7048924264d1e70e08fb2a7e6527d32b7ab1bb993ac59964ff397", "nversion=1"],