[test] make submit optional in CreateValidMempoolTransaction

This allows us to easily create transaction chains for package
validation. We don't test_accept if submit=false because we want to be
able to make transactions that wouldn't pass ATMP (i.e. a child
transaction in a package would fail due to missing inputs).

src/test/util/setup_common.cpp

@@ -263,7 +263,8 @@ CMutableTransaction TestChain100Setup::CreateValidMempoolTransaction(CTransactio
                                                                      int input_height,
                                                                      CKey input_signing_key,
                                                                      CScript output_destination,
-                                                                     CAmount output_amount)
+                                                                     CAmount output_amount,
+                                                                     bool submit)
 {
     // Transaction we will submit to the mempool
     CMutableTransaction mempool_txn;
@@ -296,8 +297,8 @@ CMutableTransaction TestChain100Setup::CreateValidMempoolTransaction(CTransactio
     std::map<int, std::string> input_errors;
     assert(SignTransaction(mempool_txn, &keystore, input_coins, nHashType, input_errors));
 
-    // Add transaction to the mempool
-    {
+    // If submit=true, add transaction to the mempool.
+    if (submit) {
         LOCK(cs_main);
         const MempoolAcceptResult result = AcceptToMemoryPool(::ChainstateActive(), *m_node.mempool.get(), MakeTransactionRef(mempool_txn), /* bypass_limits */ false);
         assert(result.m_result_type == MempoolAcceptResult::ResultType::VALID);

src/test/util/setup_common.h

@@ -135,13 +135,15 @@ struct TestChain100Setup : public RegTestingSetup {
      * @param input_signing_key  The key to spend the input_transaction
      * @param output_destination Where to send the output
      * @param output_amount      How much to send
+     * @param submit             Whether or not to submit to mempool
      */
     CMutableTransaction CreateValidMempoolTransaction(CTransactionRef input_transaction,
                                                       int input_vout,
                                                       int input_height,
                                                       CKey input_signing_key,
                                                       CScript output_destination,
-                                                      CAmount output_amount = CAmount(1 * COIN));
+                                                      CAmount output_amount = CAmount(1 * COIN),
+                                                      bool submit = true);
 
     ~TestChain100Setup();