[qa] Test for duplicate inputs within a transaction

test/functional/p2p_invalid_block.py

@@ -81,6 +81,16 @@ class InvalidBlockRequestTest(BitcoinTestFramework):
 
         node.p2p.send_blocks_and_test([block2], node, success=False, request_block=False, reject_reason='bad-txns-duplicate')
 
+        # Check transactions for duplicate inputs
+        self.log.info("Test duplicate input block.")
+
+        block2_orig.vtx[2].vin.append(block2_orig.vtx[2].vin[0])
+        block2_orig.vtx[2].rehash()
+        block2_orig.hashMerkleRoot = block2_orig.calc_merkle_root()
+        block2_orig.rehash()
+        block2_orig.solve()
+        node.p2p.send_blocks_and_test([block2_orig], node, success=False, request_block=False, reject_reason='bad-txns-inputs-duplicate')
+
         self.log.info("Test very broken block.")
 
         block3 = create_block(tip, create_coinbase(height), block_time)