[refactor/test] Extract P2PTxInvStore into test framework

test/functional/test_framework/mininode.py

@@ -12,7 +12,10 @@ found in the mini-node branch of http://github.com/jgarzik/pynode.
 P2PConnection: A low-level connection object to a node's P2P interface
 P2PInterface: A high-level interface object for communicating to a node over P2P
 P2PDataStore: A p2p interface class that keeps a store of transactions and blocks
-              and can respond correctly to getdata and getheaders messages"""
+              and can respond correctly to getdata and getheaders messages
+P2PTxInvStore: A p2p interface class that inherits from P2PDataStore, and keeps
+              a count of how many times each txid has been announced."""
+
 import asyncio
 from collections import defaultdict
 from io import BytesIO
@@ -606,3 +609,20 @@ class P2PDataStore(P2PInterface):
                 # Check that none of the txs are now in the mempool
                 for tx in txs:
                     assert tx.hash not in raw_mempool, "{} tx found in mempool".format(tx.hash)
+
+class P2PTxInvStore(P2PInterface):
+    """A P2PInterface which stores a count of how many times each txid has been announced."""
+    def __init__(self):
+        super().__init__()
+        self.tx_invs_received = defaultdict(int)
+
+    def on_inv(self, message):
+        # Store how many times invs have been received for each tx.
+        for i in message.inv:
+            if i.type == MSG_TX:
+                # save txid
+                self.tx_invs_received[i.hash] += 1
+
+    def get_invs(self):
+        with mininode_lock:
+            return list(self.tx_invs_received.keys())