diff --git a/test/functional/abc-invalid-message.py b/test/functional/abc-invalid-message.py
--- a/test/functional/abc-invalid-message.py
+++ b/test/functional/abc-invalid-message.py
@@ -12,7 +12,6 @@
 
 from test_framework.messages import NODE_NETWORK, msg_version
 from test_framework.mininode import (
-    MAGIC_BYTES,
     mininode_lock,
     msg_ping,
     P2PInterface,
@@ -26,7 +25,7 @@
 
     data = original_message.serialize()
     i = 0
-    i += len(MAGIC_BYTES[connection.network])
+    i += len(connection.magic_bytes)
     i += 12
     i += len(struct.pack("<I", len(data)))
 
diff --git a/test/functional/p2p_invalid_messages.py b/test/functional/p2p_invalid_messages.py
--- a/test/functional/p2p_invalid_messages.py
+++ b/test/functional/p2p_invalid_messages.py
@@ -15,7 +15,7 @@
 
     command = b'badmsg'
 
-    def __init__(self, str_data):
+    def __init__(self, *, str_data):
         self.str_data = str_data.encode() if not isinstance(str_data, bytes) else str_data
 
     def serialize(self):
@@ -25,19 +25,14 @@
         return "{}(data={})".format(self.command, self.str_data)
 
 
-class msg_nametoolong(msg_unrecognized):
-
-    command = b'thisnameiswayyyyyyyyytoolong'
-
-
 class InvalidMessagesTest(BitcoinTestFramework):
-
     def set_test_params(self):
         self.num_nodes = 1
         self.setup_clean_chain = True
 
     def run_test(self):
         """
+         . Test msg header
         0. Send a bunch of large (2MB) messages of an unrecognized type. Check to see
            that it isn't an effective DoS against the node.
 
@@ -45,10 +40,12 @@
 
         2. Send a few messages with an incorrect data size in the header, ensure the
            messages are ignored.
-
-        3. Send an unrecognized message with a command name longer than 12 characters.
-
         """
+        self.test_magic_bytes()
+        self.test_checksum()
+        self.test_size()
+        self.test_command()
+
         node = self.nodes[0]
         self.node = node
         node.add_p2p_connection(P2PDataStore())
@@ -65,7 +62,7 @@
         # Send as large a message as is valid, ensure we aren't disconnected but
         # also can't exhaust resources.
         #
-        msg_at_size = msg_unrecognized("b" * valid_data_limit)
+        msg_at_size = msg_unrecognized(str_data="b" * valid_data_limit)
         assert len(msg_at_size.serialize()) == msg_limit
 
         self.log.info(
@@ -91,7 +88,7 @@
         #
         # Send an oversized message, ensure we're disconnected.
         #
-        msg_over_size = msg_unrecognized("b" * (valid_data_limit + 1))
+        msg_over_size = msg_unrecognized(str_data="b" * (valid_data_limit + 1))
         assert len(msg_over_size.serialize()) == (msg_limit + 1)
 
         with node.assert_debug_log(["Oversized header detected"]):
@@ -110,7 +107,7 @@
         # Send messages with an incorrect data size in the header.
         #
         actual_size = 100
-        msg = msg_unrecognized("b" * actual_size)
+        msg = msg_unrecognized(str_data="b" * actual_size)
 
         # TODO: handle larger-than cases. I haven't been able to pin down what
         # behavior to expect.
@@ -141,18 +138,65 @@
             node.disconnect_p2ps()
             node.add_p2p_connection(P2PDataStore())
 
-        #
-        # 3.
-        #
-        # Send a message with a too-long command name.
-        #
-        node.p2p.send_message(msg_nametoolong("foobar"))
-        node.p2p.wait_for_disconnect(timeout=4)
-
         # Node is still up.
         conn = node.add_p2p_connection(P2PDataStore())
         conn.sync_with_ping()
 
+    def test_magic_bytes(self):
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        conn.magic_bytes = b'\x00\x11\x22\x32'
+        with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: INVALID MESSAGESTART ping']):
+            conn.send_message(messages.msg_ping(nonce=0xff))
+            conn.wait_for_disconnect(timeout=1)
+            self.nodes[0].disconnect_p2ps()
+
+    def test_checksum(self):
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        with self.nodes[0].assert_debug_log(['ProcessMessages(badmsg, 2 bytes): CHECKSUM ERROR expected 78df0a04 was ffffffff']):
+            msg = conn.build_message(msg_unrecognized(str_data="d"))
+            cut_len = (
+                # magic
+                4 +
+                # command
+                12 +
+                # len
+                4
+            )
+            # modify checksum
+            msg = msg[:cut_len] + b'\xff' * 4 + msg[cut_len + 4:]
+            self.nodes[0].p2p.send_raw_message(msg)
+            conn.wait_for_disconnect()
+            self.nodes[0].disconnect_p2ps()
+
+    def test_size(self):
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        with self.nodes[0].assert_debug_log(['']):
+            msg = conn.build_message(msg_unrecognized(str_data="d"))
+            cut_len = (
+                # magic
+                4 +
+                # command
+                12
+            )
+            # modify len to MAX_SIZE + 1
+            msg = msg[:cut_len] + \
+                struct.pack("<I", 0x02000000 + 1) + msg[cut_len + 4:]
+            self.nodes[0].p2p.send_raw_message(msg)
+            conn.wait_for_disconnect(timeout=1)
+            self.nodes[0].disconnect_p2ps()
+
+    def test_command(self):
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: ERRORS IN HEADER']):
+            msg = msg_unrecognized(str_data="d")
+            msg.command = b'\xff' * 12
+            msg = conn.build_message(msg)
+            # Modify command
+            msg = msg[:7] + b'\x00' + msg[7 + 1:]
+            self.nodes[0].p2p.send_raw_message(msg)
+            conn.sync_with_ping(timeout=1)
+            self.nodes[0].disconnect_p2ps()
+
     def _tweak_msg_data_size(self, message, wrong_size):
         """
         Return a raw message based on another message but with an incorrect data size in
diff --git a/test/functional/test_framework/mininode.py b/test/functional/test_framework/mininode.py
--- a/test/functional/test_framework/mininode.py
+++ b/test/functional/test_framework/mininode.py
@@ -123,7 +123,7 @@
         self.on_connection_send_msg = None
         self.on_connection_send_msg_is_raw = False
         self.recvbuf = b""
-        self.network = net
+        self.magic_bytes = MAGIC_BYTES[net]
         logger.debug('Connecting to Bitcoin Node: {}:{}'.format(
             self.dstaddr, self.dstport))
 
@@ -193,7 +193,7 @@
             with mininode_lock:
                 if len(self.recvbuf) < 4:
                     return None
-                if self.recvbuf[:4] != MAGIC_BYTES[self.network]:
+                if self.recvbuf[:4] != self.magic_bytes:
                     raise ValueError(
                         "got garbage {}".format(repr(self.recvbuf)))
                 if len(self.recvbuf) < 4 + 12 + 4 + 4:
@@ -260,7 +260,7 @@
         """Build a serialized P2P message"""
         command = message.command
         data = message.serialize()
-        tmsg = MAGIC_BYTES[self.network]
+        tmsg = self.magic_bytes
         tmsg += command
         tmsg += b"\x00" * (12 - len(command))
         tmsg += struct.pack("<I", len(data))