test: add rpc_generate functional test

Author: jonatack

test/functional/rpc_generate.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+# Copyright (c) 2020 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test generate RPC."""
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import (
+    assert_equal,
+    assert_raises_rpc_error,
+)
+
+
+class RPCGenerateTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+
+    def run_test(self):
+        message = (
+            "generate ( nblocks maxtries ) has been replaced by the -generate "
+            "cli option. Refer to -help for more information."
+        )
+
+        self.log.info("Test rpc generate raises with message to use cli option")
+        assert_raises_rpc_error(-32601, message, self.nodes[0].rpc.generate)
+
+        self.log.info("Test rpc generate help prints message to use cli option")
+        assert_equal(message, self.nodes[0].help("generate"))
+
+        self.log.info("Test rpc generate is a hidden command not discoverable in general help")
+        assert message not in self.nodes[0].help()
+
+
+if __name__ == "__main__":
+    RPCGenerateTest().main()

test/functional/test_runner.py

@@ -193,6 +193,7 @@
     'p2p_eviction.py',
     'rpc_signmessage.py',
     'rpc_generateblock.py',
+    'rpc_generate.py',
     'wallet_balance.py',
     'feature_nulldummy.py',
     'mempool_accept.py',