test: check for specific disconnect reasons in p2p_blockfilters.py

This ensures that the disconnect happens for the expected reason and
also makes it easier to navigate between implementation and test code,
i.e. both the questions "do we have test coverage for this disconnect?"
(from an implementation reader's perspective) and "where is the code
handling this disconnect?" (from a test reader's perspective) can be
answered simply by grep-ping the corresponding debug message.

Can be easiest reviewed with `-w` (to ignore whitespace changes).

Author: theStack

test/functional/p2p_blockfilters.py

@@ -211,38 +211,48 @@ def run_test(self):
         ]
         for request in requests:
             peer_1 = self.nodes[1].add_p2p_connection(P2PInterface())
-            peer_1.send_message(request)
-            peer_1.wait_for_disconnect()
+            with self.nodes[1].assert_debug_log(expected_msgs=["requested unsupported block filter type"]):
+                peer_1.send_message(request)
+                peer_1.wait_for_disconnect()
 
         self.log.info("Check that invalid requests result in disconnection.")
         requests = [
             # Requesting too many filters results in disconnection.
-            msg_getcfilters(
-                filter_type=FILTER_TYPE_BASIC,
-                start_height=0,
-                stop_hash=int(main_block_hash, 16),
+            (
+                msg_getcfilters(
+                    filter_type=FILTER_TYPE_BASIC,
+                    start_height=0,
+                    stop_hash=int(main_block_hash, 16),
+                ), "requested too many cfilters/cfheaders"
             ),
             # Requesting too many filter headers results in disconnection.
-            msg_getcfheaders(
-                filter_type=FILTER_TYPE_BASIC,
-                start_height=0,
-                stop_hash=int(tip_hash, 16),
+            (
+                msg_getcfheaders(
+                    filter_type=FILTER_TYPE_BASIC,
+                    start_height=0,
+                    stop_hash=int(tip_hash, 16),
+                ), "requested too many cfilters/cfheaders"
             ),
             # Requesting unknown filter type results in disconnection.
-            msg_getcfcheckpt(
-                filter_type=255,
-                stop_hash=int(main_block_hash, 16),
+            (
+                msg_getcfcheckpt(
+                    filter_type=255,
+                    stop_hash=int(main_block_hash, 16),
+                ), "requested unsupported block filter type"
             ),
             # Requesting unknown hash results in disconnection.
-            msg_getcfcheckpt(
-                filter_type=FILTER_TYPE_BASIC,
-                stop_hash=123456789,
+            (
+                msg_getcfcheckpt(
+                    filter_type=FILTER_TYPE_BASIC,
+                    stop_hash=123456789,
+                ), "requested invalid block hash"
             ),
         ]
-        for request in requests:
+        for request, expected_log_msg in requests:
             peer_0 = self.nodes[0].add_p2p_connection(P2PInterface())
-            peer_0.send_message(request)
-            peer_0.wait_for_disconnect()
+            with self.nodes[0].assert_debug_log(expected_msgs=[expected_log_msg]):
+                peer_0.send_message(request)
+                peer_0.wait_for_disconnect()
 
         self.log.info("Test -peerblockfilters without -blockfilterindex raises an error")
         self.stop_node(0)