test: passing invalid -onion raises expected init error

test/functional/feature_proxy.py

@@ -32,6 +32,7 @@ addnode connect to a CJDNS address
 - Test getnetworkinfo for each node
 
 - Test passing invalid -proxy
+- Test passing invalid -onion
 """
 
 import socket
@@ -313,6 +314,11 @@ class ProxyTest(BitcoinTestFramework):
         msg = "Error: Invalid -proxy address or hostname: 'abc:def'"
         self.nodes[1].assert_start_raises_init_error(expected_msg=msg)
 
+        self.log.info("Test passing invalid -onion raises expected init error")
+        self.nodes[1].extra_args = ["-onion=xyz:abc"]
+        msg = "Error: Invalid -onion address or hostname: 'xyz:abc'"
+        self.nodes[1].assert_start_raises_init_error(expected_msg=msg)
+
 
 if __name__ == '__main__':
     ProxyTest().main()