Persist Sapling key material in the wallet to disk

qa/pull-tester/rpc-tests.sh

@@ -23,6 +23,7 @@ testScripts=(
     'wallet_mergetoaddress.py'
     'wallet.py'
     'wallet_overwintertx.py'
+    'wallet_persistence.py'
     'wallet_nullifiers.py'
     'wallet_1941.py'
     'wallet_addresses.py'

qa/rpc-tests/wallet_persistence.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python2
+# Copyright (c) 2018 The Zcash developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_true, start_nodes, stop_nodes, \
+    wait_bitcoinds
+
+class WalletPersistenceTest (BitcoinTestFramework):
+
+    def setup_network(self, split=False):
+        self.nodes = start_nodes(1, self.options.tmpdir)
+        self.is_network_split = False
+        self.sync_all()
+
+    def run_test(self):
+        sapling_addr = self.nodes[0].z_getnewaddress('sapling')
+        addresses = self.nodes[0].z_listaddresses()
+        # make sure the node has the addresss
+        assert_true(sapling_addr in addresses, "Should contain address before restart")
+        # restart the nodes
+        stop_nodes(self.nodes)
+        wait_bitcoinds()
+        self.nodes = self.setup_nodes()
+        addresses = self.nodes[0].z_listaddresses()
+        # make sure we still have the address after restarting
+        assert_true(sapling_addr in addresses, "Should contain address after restart")
+
+if __name__ == '__main__':
+    WalletPersistenceTest().main()