Merge bitcoin/bitcoin#25173: test: add coverage for unknown network in -onlynet

055d94d test: add coverage for unknown network in -onlynet (brunoerg)

Pull request description:

  This PR adds test coverage for the following init error by passing an unknown network in -onlynet
  https://github.com/bitcoin/bitcoin/blob/0de36941eca1bff91420dd878eb097db2b1a596c/src/init.cpp#L1311

ACKs for top commit:
  MarcoFalke:
    rACK 055d94d

Tree-SHA512: 01bbb297afff371f6345889fa04117ff195b68f0bbf934878ba446049791fdbd7d2ce119ee4f9b3616cc0a81330d7055507dc81151acf68532c077f3575258e9

Author: MacroFake

test/functional/feature_proxy.py

@@ -36,6 +36,7 @@
 - Test passing invalid -i2psam
 - Test passing -onlynet=onion without -proxy or -onion
 - Test passing -onlynet=onion with -onion=0 and with -noonion
+- Test passing unknown -onlynet
 """
 
 import socket
@@ -349,6 +350,11 @@ def networks_dict(d):
             self.nodes[1].extra_args = ["-onlynet=onion", arg]
             self.nodes[1].assert_start_raises_init_error(expected_msg=msg)
 
+        self.log.info("Test passing unknown network to -onlynet raises expected init error")
+        self.nodes[1].extra_args = ["-onlynet=abc"]
+        msg = "Error: Unknown network specified in -onlynet: 'abc'"
+        self.nodes[1].assert_start_raises_init_error(expected_msg=msg)
+
 
 if __name__ == '__main__':
     ProxyTest().main()