added extreme tx tests

Author: karask

TODO

@@ -54,8 +54,6 @@ OTHERLIBS-related
 
 OTHER
 - create script: clean-less-than-sats 100000 bc1q86gsg4t32...
-- create test with 260 outputs (inputs too much trouble) - file: test_extreme_txs.py
-- create test with script of 260 and another with 66000 commands
 - maybe make RBF the default from now on (like Bitcoin Core)
   . will need to change all the tests, unless I add minor hack that uses RBF by default only for taproot
 

bitcoinutils/script.py

@@ -293,16 +293,15 @@ def _op_push_data(self, data: str) -> bytes:
         Also note that according to standarardness rules (BIP-62) the minimum
         possible PUSHDATA operator must be used!
         """
-        
-        data_bytes = h_to_b(data) # Assuming string is hexadecimal
+        data_bytes = h_to_b(data)
 
         if len(data_bytes) < 0x4C:
             return bytes([len(data_bytes)]) + data_bytes
-        elif len(data_bytes) < 0xFF:
+        elif len(data_bytes) <= 0xFF:
             return b"\x4c" + bytes([len(data_bytes)]) + data_bytes
-        elif len(data_bytes) < 0xFFFF:
+        elif len(data_bytes) <= 0xFFFF:
             return b"\x4d" + struct.pack("<H", len(data_bytes)) + data_bytes
-        elif len(data_bytes) < 0xFFFFFFFF:
+        elif len(data_bytes) <= 0xFFFFFFFF:
             return b"\x4e" + struct.pack("<I", len(data_bytes)) + data_bytes
         else:
             raise ValueError("Data too large. Cannot push into script")

tests/test_extreme_txs.py

@@ -0,0 +1,87 @@
+# Copyright (C) 2018-2025 The python-bitcoin-utils developers
+#
+# This file is part of python-bitcoin-utils
+#
+# It is subject to the license terms in the LICENSE file found in the top-level
+# directory of this distribution.
+#
+# No part of python-bitcoin-utils, including this file, may be copied,
+# modified, propagated, or distributed except according to the terms contained
+# in the LICENSE file.
+
+import unittest
+
+from bitcoinutils.keys import P2pkhAddress
+from bitcoinutils.script import Script
+from bitcoinutils.setup import setup
+from bitcoinutils.transactions import Transaction, TxInput, TxOutput
+
+
+class TestExtremeTransactions(unittest.TestCase):
+    def setUp(self):
+        setup("testnet")
+        self.txin = TxInput(
+            "11" * 32,
+            0,
+            sequence=b"\xff\xff\xff\xff",
+        )
+        self.script_pubkey = P2pkhAddress(
+            "mytmhndz4UbEMeoSZorXXrLpPfeoFUDzEp"
+        ).to_script_pub_key()
+
+    def _assert_script_length_prefix(self, commands, expected_prefix):
+        script = Script(commands)
+        tx = Transaction([self.txin], [TxOutput(1000, script)])
+
+        raw = tx.serialize()
+
+        # version + input count + one input with empty scriptSig + output count
+        # + output amount
+        script_length_offset = (4 + 1 + 32 + 4 + 1 + 4 + 1 + 8) * 2
+        self.assertEqual(
+            raw[script_length_offset : script_length_offset + len(expected_prefix)],
+            expected_prefix,
+        )
+
+        parsed_tx = Transaction.from_raw(raw)
+        self.assertEqual(len(parsed_tx.outputs[0].script_pubkey.script), len(commands))
+        self.assertEqual(parsed_tx.serialize(), raw)
+
+    def test_transaction_with_260_outputs_uses_compact_size(self):
+        outputs = [TxOutput(1000 + i, self.script_pubkey) for i in range(260)]
+        tx = Transaction([self.txin], outputs)
+
+        raw = tx.serialize()
+
+        # version + input count + one input with empty scriptSig
+        output_count_offset = (4 + 1 + 32 + 4 + 1 + 4) * 2
+        self.assertEqual(raw[output_count_offset : output_count_offset + 6], "fd0401")
+
+        parsed_tx = Transaction.from_raw(raw)
+        self.assertEqual(len(parsed_tx.outputs), 260)
+        self.assertEqual(parsed_tx.serialize(), raw)
+
+    def test_script_with_260_commands_uses_compact_size_uint16(self):
+        self._assert_script_length_prefix(["OP_1"] * 260, "fd0401")
+
+    def test_script_with_66000_commands_uses_compact_size_uint32(self):
+        self._assert_script_length_prefix(["OP_1"] * 66000, "fed0010100")
+
+    def test_pushdata_boundaries_use_minimal_opcode(self):
+        cases = [
+            (75, "4b"),
+            (76, "4c4c"),
+            (255, "4cff"),
+            (256, "4d0001"),
+            (65535, "4dffff"),
+            (65536, "4e00000100"),
+        ]
+
+        for size, expected_prefix in cases:
+            with self.subTest(size=size):
+                raw = Script(["aa" * size]).to_hex()
+                self.assertEqual(raw[: len(expected_prefix)], expected_prefix)
+
+
+if __name__ == "__main__":
+    unittest.main()