test: Use extra_port() helper in feature_bind_extra.py

test/functional/feature_bind_extra.py

@@ -37,37 +37,41 @@ class BindExtraTest(BitcoinTestFramework):
         loopback_ipv4 = addr_to_hex("127.0.0.1")
 
         # Start custom ports by reusing unused p2p ports
-        port = p2p_port(self.num_nodes)
+        def extra_port():
+            port = p2p_port(extra_port.index)
+            extra_port.index += 1
+            return port
+        extra_port.index = self.num_nodes
 
         # Array of tuples [command line arguments, expected bind addresses].
         self.expected = []
 
         # Node0, no normal -bind=... with -bind=...=onion, thus only the tor target.
+        port = extra_port()
         self.expected.append(
             [
                 [f"-bind=127.0.0.1:{port}=onion"],
-                [(loopback_ipv4, port)]
+                [(loopback_ipv4, port)],
             ],
         )
-        port += 1
 
         # Node1, both -bind=... and -bind=...=onion.
+        port = [extra_port(), extra_port()]
         self.expected.append(
             [
-                [f"-bind=127.0.0.1:{port}", f"-bind=127.0.0.1:{port + 1}=onion"],
-                [(loopback_ipv4, port), (loopback_ipv4, port + 1)]
+                [f"-bind=127.0.0.1:{port[0]}", f"-bind=127.0.0.1:{port[1]}=onion"],
+                [(loopback_ipv4, port[0]), (loopback_ipv4, port[1])],
             ],
         )
-        port += 2
 
         # Node2, no -bind=...=onion, thus no extra port for Tor target.
+        port = extra_port()
         self.expected.append(
             [
                 [f"-bind=127.0.0.1:{port}"],
-                [(loopback_ipv4, port)]
+                [(loopback_ipv4, port)],
             ],
         )
-        port += 1
 
         self.extra_args = list(map(lambda e: e[0], self.expected))
         self.setup_nodes()