test: add unit test for non-standard txs with too large tx size

The function IsStandardTx() returns rejection reason "tx-size" if the
transaction weight is larger than MAX_STANDARD_TX_WEIGHT (=400000 vbytes).

Author: theStack

src/test/transaction_tests.cpp

@@ -821,9 +821,29 @@ BOOST_AUTO_TEST_CASE(test_IsStandard)
     BOOST_CHECK(!IsStandardTx(CTransaction(t), reason));
     BOOST_CHECK_EQUAL(reason, "scriptsig-size");
 
+    // Check tx-size (non-standard if transaction weight is > MAX_STANDARD_TX_WEIGHT)
+    t.vin.clear();
+    t.vin.resize(2438); // size per input (empty scriptSig): 41 bytes
+    t.vout[0].scriptPubKey = CScript() << OP_RETURN << std::vector<unsigned char>(19, 0); // output size: 30 bytes
+    // tx header:                12 bytes =>     48 vbytes
+    // 2438 inputs: 2438*41 = 99958 bytes => 399832 vbytes
+    //    1 output:              30 bytes =>    120 vbytes
+    //                      ===============================
+    //                                total: 400000 vbytes
+    BOOST_CHECK_EQUAL(GetTransactionWeight(CTransaction(t)), 400000);
+    BOOST_CHECK(IsStandardTx(CTransaction(t), reason));
+
+    // increase output size by one byte, so we end up with 400004 vbytes
+    t.vout[0].scriptPubKey = CScript() << OP_RETURN << std::vector<unsigned char>(20, 0); // output size: 31 bytes
+    BOOST_CHECK_EQUAL(GetTransactionWeight(CTransaction(t)), 400004);
+    reason.clear();
+    BOOST_CHECK(!IsStandardTx(CTransaction(t), reason));
+    BOOST_CHECK_EQUAL(reason, "tx-size");
+
     // Check bare multisig (standard if policy flag fIsBareMultisigStd is set)
     fIsBareMultisigStd = true;
     t.vout[0].scriptPubKey = GetScriptForMultisig(1, {key.GetPubKey()}); // simple 1-of-1
+    t.vin.resize(1);
     t.vin[0].scriptSig = CScript() << std::vector<unsigned char>(65, 0);
     BOOST_CHECK(IsStandardTx(CTransaction(t), reason));