test: Introduce ensure_for helper

test/functional/mempool_unbroadcast.py

@@ -5,11 +5,12 @@
 """Test that the mempool ensures transaction delivery by periodically sending
 to peers until a GETDATA is received."""
 
-import time
-
 from test_framework.p2p import P2PTxInvStore
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal
+from test_framework.util import (
+    assert_equal,
+    ensure_for,
+)
 from test_framework.wallet import MiniWallet
 
 MAX_INITIAL_BROADCAST_DELAY = 15 * 60 # 15 minutes in seconds
@@ -83,8 +84,8 @@ class MempoolUnbroadcastTest(BitcoinTestFramework):
 
         conn = node.add_p2p_connection(P2PTxInvStore())
         node.mockscheduler(MAX_INITIAL_BROADCAST_DELAY)
-        time.sleep(2) # allow sufficient time for possibility of broadcast
-        assert_equal(len(conn.get_invs()), 0)
+        # allow sufficient time for possibility of broadcast
+        ensure_for(duration=2, f=lambda: len(conn.get_invs()) == 0)
 
         self.disconnect_nodes(0, 1)
         node.disconnect_p2ps()