feat: Add Transaction input/output helper methods and extreme tx test

bitcoinutils/transactions.py

@@ -767,6 +767,44 @@ def get_transaction_digest(
 
         return tx_digest
 
+    def add_input(self, input: TxInput):
+        """Adds an input to the transaction (and an empty witness if segwit)"""
+        self.inputs.append(input)
+        if self.has_segwit:
+            self.witnesses.append(TxWitnessInput([]))
+
+    def update_input(self, index: int, input: TxInput):
+        """Updates an input at the specified index"""
+        if index < 0 or index >= len(self.inputs):
+            raise IndexError("Transaction input index out of range")
+        self.inputs[index] = input
+
+    def remove_input(self, index: int):
+        """Removes an input at the specified index (and its witness if segwit)"""
+        if index < 0 or index >= len(self.inputs):
+            raise IndexError("Transaction input index out of range")
+        del self.inputs[index]
+        if self.has_segwit:
+            # assuming witnesses logic is consistent with inputs length
+            if index < len(self.witnesses):
+                del self.witnesses[index]
+
+    def add_output(self, output: TxOutput):
+        """Adds an output to the transaction"""
+        self.outputs.append(output)
+
+    def update_output(self, index: int, output: TxOutput):
+        """Updates an output at the specified index"""
+        if index < 0 or index >= len(self.outputs):
+            raise IndexError("Transaction output index out of range")
+        self.outputs[index] = output
+
+    def remove_output(self, index: int):
+        """Removes an output at the specified index"""
+        if index < 0 or index >= len(self.outputs):
+            raise IndexError("Transaction output index out of range")
+        del self.outputs[index]
+
     def get_transaction_segwit_digest(
         self, txin_index: int, script: Script, amount: int, sighash: int = SIGHASH_ALL
     ):

tests/test_extreme_txs.py

@@ -0,0 +1,30 @@
+
+import unittest
+from bitcoinutils.transactions import Transaction, TxInput, TxOutput
+from bitcoinutils.script import Script
+
+class TestExtremeTransactions(unittest.TestCase):
+    def test_many_outputs(self):
+        """Test transaction with 260 outputs"""
+        tx = Transaction()
+        # Add one input
+        tx.add_input(TxInput("a"*64, 0, Script([])))
+
+        # Add 260 outputs
+        # 260 is chosen because it might trigger varint boundaries or size limits if logic is flawed
+        # For varint: 253 is the boundary where it switches from 1 byte to 3 bytes (fd xx xx)
+        # So 260 ensures we cover the multi-byte varint case for number of outputs.
+        for i in range(260):
+            tx.add_output(TxOutput(i, Script([])))
+
+        # Serialize and check size
+        raw_tx = tx.to_bytes(has_segwit=False)
+        self.assertTrue(len(raw_tx) > 0)
+
+        # Verify we can deserialize it
+        tx_from_raw = Transaction.from_raw(raw_tx)
+        self.assertEqual(len(tx_from_raw.outputs), 260)
+        self.assertEqual(tx_from_raw.outputs[-1].amount, 259)
+
+if __name__ == '__main__':
+    unittest.main()

tests/test_transaction_helpers.py

@@ -0,0 +1,59 @@
+
+import unittest
+from bitcoinutils.transactions import Transaction, TxInput, TxOutput, TxWitnessInput
+from bitcoinutils.script import Script
+
+class TestTransactionHelpers(unittest.TestCase):
+    def setUp(self):
+        self.tx_in = TxInput("txid", 0, Script(["OP_0"]))
+        self.tx_out = TxOutput(1000, Script(["OP_1"]))
+        self.tx = Transaction()
+
+    def test_add_input(self):
+        self.tx.add_input(self.tx_in)
+        self.assertEqual(len(self.tx.inputs), 1)
+        self.assertEqual(self.tx.inputs[0], self.tx_in)
+
+    def test_add_input_segwit(self):
+        self.tx.has_segwit = True
+        self.tx.add_input(self.tx_in)
+        self.assertEqual(len(self.tx.inputs), 1)
+        self.assertEqual(len(self.tx.witnesses), 1)
+        self.assertIsInstance(self.tx.witnesses[0], TxWitnessInput)
+
+    def test_remove_input(self):
+        self.tx.add_input(self.tx_in)
+        self.tx.remove_input(0)
+        self.assertEqual(len(self.tx.inputs), 0)
+
+    def test_remove_input_segwit(self):
+        self.tx.has_segwit = True
+        self.tx.add_input(self.tx_in) # adds witness
+        self.tx.remove_input(0) # should remove witness
+        self.assertEqual(len(self.tx.inputs), 0)
+        self.assertEqual(len(self.tx.witnesses), 0)
+
+    def test_update_input(self):
+        self.tx.add_input(self.tx_in)
+        new_in = TxInput("new_txid", 1, Script(["OP_2"]))
+        self.tx.update_input(0, new_in)
+        self.assertEqual(self.tx.inputs[0], new_in)
+
+    def test_add_output(self):
+        self.tx.add_output(self.tx_out)
+        self.assertEqual(len(self.tx.outputs), 1)
+        self.assertEqual(self.tx.outputs[0], self.tx_out)
+
+    def test_remove_output(self):
+        self.tx.add_output(self.tx_out)
+        self.tx.remove_output(0)
+        self.assertEqual(len(self.tx.outputs), 0)
+
+    def test_update_output(self):
+        self.tx.add_output(self.tx_out)
+        new_out = TxOutput(2000, Script(["OP_3"]))
+        self.tx.update_output(0, new_out)
+        self.assertEqual(self.tx.outputs[0], new_out)
+
+if __name__ == '__main__':
+    unittest.main()