diff --git a/test/functional/feature_help.py b/test/functional/feature_help.py
--- a/test/functional/feature_help.py
+++ b/test/functional/feature_help.py
@@ -39,7 +39,11 @@
         output = self.nodes[0].process.stdout.read()
         assert b'version' in output
         self.log.info("Version text received: {} (...)".format(output[0:60]))
+        # Clean up TestNode state
         self.nodes[0].running = False
+        self.nodes[0].process = None
+        self.nodes[0].rpc_connected = False
+        self.nodes[0].rpc = None
 
 
 if __name__ == '__main__':
diff --git a/test/functional/test_framework/test_framework.py b/test/functional/test_framework/test_framework.py
--- a/test/functional/test_framework/test_framework.py
+++ b/test/functional/test_framework/test_framework.py
@@ -160,6 +160,8 @@
             if self.nodes:
                 self.stop_nodes()
         else:
+            for node in self.nodes:
+                node.cleanup_on_exit = False
             self.log.info(
                 "Note: bitcoinds were not stopped and may still be running")
 
diff --git a/test/functional/test_framework/test_node.py b/test/functional/test_framework/test_node.py
--- a/test/functional/test_framework/test_node.py
+++ b/test/functional/test_framework/test_node.py
@@ -96,9 +96,20 @@
         self.url = None
         self.relay_fee_cache = None
         self.log = logging.getLogger('TestFramework.node{}'.format(i))
-
+        # Whether to kill the node when this object goes away
+        self.cleanup_on_exit = True
         self.p2ps = []
 
+    def __del__(self):
+        # Ensure that we don't leave any bitcoind processes lying around after
+        # the test ends
+        if self.process and self.cleanup_on_exit:
+            # Should only happen on test failure
+            # Avoid using logger, as that may have already been shutdown when
+            # this destructor is called.
+            print("Cleaning up leftover process")
+            self.process.kill()
+
     def __getattr__(self, name):
         """Dispatches any unrecognised messages to the RPC connection or a CLI instance."""
         if self.use_cli: