Testcase for wallet issue with orphaned rewards.

This adds a new test case demonstrating the wallet issue when block
rewards are orphaned (https://github.com/bitcoin/bitcoin/issues/14148).

test/functional/test_runner.py

@@ -283,6 +283,7 @@ BASE_SCRIPTS = [
     'feature_logging.py',
     'feature_anchors.py',
     'feature_coinstatsindex.py',
+    'wallet_orphanedreward.py',
     'p2p_node_network_limited.py',
     'p2p_permissions.py',
     'feature_blocksdir.py',

test/functional/wallet_orphanedreward.py

@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+# Copyright (c) 2020-2021 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 orphaned block rewards in the wallet."""
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+class OrphanedBlockRewardTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.setup_clean_chain = True
+        self.num_nodes = 2
+
+    def skip_test_if_missing_module(self):
+        self.skip_if_no_wallet()
+
+    def run_test(self):
+        # Generate some blocks and obtain some coins on node 0.  We send
+        # some balance to node 1, which will hold it as a single coin.
+        self.nodes[0].generate(150)
+        self.nodes[0].sendtoaddress(self.nodes[1].getnewaddress(), 10)
+        self.nodes[0].generate(1)
+
+        # Get a block reward with node 1 and remember the block so we can orphan
+        # it later.
+        self.sync_blocks()
+        blk = self.nodes[1].generate(1)[0]
+        self.sync_blocks()
+
+        # Let the block reward mature and send coins including both
+        # the existing balance and the block reward.
+        self.nodes[0].generate(150)
+        assert_equal(self.nodes[1].getbalance(), 10 + 25)
+        txid = self.nodes[1].sendtoaddress(self.nodes[0].getnewaddress(), 30)
+
+        # Orphan the block reward and make sure that the original coins
+        # from the wallet can still be spent.
+        self.nodes[0].invalidateblock(blk)
+        self.nodes[0].generate(152)
+        self.sync_blocks()
+        # Without the following abandontransaction call, the coins are
+        # not considered available yet.
+        assert_equal(self.nodes[1].getbalances()["mine"], {
+          "trusted": 0,
+          "untrusted_pending": 0,
+          "immature": 0,
+        })
+        # The following abandontransaction is necessary to make the later
+        # lines succeed, and probably should not be needed; see
+        # https://github.com/bitcoin/bitcoin/issues/14148.
+        self.nodes[1].abandontransaction(txid)
+        assert_equal(self.nodes[1].getbalances()["mine"], {
+          "trusted": 10,
+          "untrusted_pending": 0,
+          "immature": 0,
+        })
+        self.nodes[1].sendtoaddress(self.nodes[0].getnewaddress(), 9)
+
+if __name__ == '__main__':
+    OrphanedBlockRewardTest().main()