Extend getchaintips RPC test.

Add the capability to simulate network splits to the RPC test framework
and use it to do more extensive testing of 'getchaintips'.

qa/rpc-tests/getchaintips.py

@@ -3,22 +3,52 @@
 # Distributed under the MIT/X11 software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-# Exercise the getchaintips API.
-
-# Since the test framework does not generate orphan blocks, we can
-# unfortunately not check for them!
+# Exercise the getchaintips API.  We introduce a network split, work
+# on chains of different lengths, and join the network together again.
+# This gives us two tips, verify that it works.
 
 from test_framework import BitcoinTestFramework
 from util import assert_equal
 
 class GetChainTipsTest (BitcoinTestFramework):
 
-    def run_test (self, nodes):
-        res = nodes[0].getchaintips ()
-        assert_equal (len (res), 1)
-        res = res[0]
-        assert_equal (res['branchlen'], 0)
-        assert_equal (res['height'], 200)
+    def run_test (self):
+        BitcoinTestFramework.run_test (self)
+
+        tips = self.nodes[0].getchaintips ()
+        assert_equal (len (tips), 1)
+        assert_equal (tips[0]['branchlen'], 0)
+        assert_equal (tips[0]['height'], 200)
+
+        # Split the network and build two chains of different lengths.
+        self.split_network ()
+        self.nodes[0].setgenerate (True, 10);
+        self.nodes[2].setgenerate (True, 20);
+        self.sync_all ()
+
+        tips = self.nodes[1].getchaintips ()
+        assert_equal (len (tips), 1)
+        shortTip = tips[0]
+        assert_equal (shortTip['branchlen'], 0)
+        assert_equal (shortTip['height'], 210)
+
+        tips = self.nodes[3].getchaintips ()
+        assert_equal (len (tips), 1)
+        longTip = tips[0]
+        assert_equal (longTip['branchlen'], 0)
+        assert_equal (longTip['height'], 220)
+
+        # Join the network halves and check that we now have two tips
+        # (at least at the nodes that previously had the short chain).
+        self.join_network ()
+
+        tips = self.nodes[0].getchaintips ()
+        assert_equal (len (tips), 2)
+        assert_equal (tips[0], longTip)
+
+        assert_equal (tips[1]['branchlen'], 10)
+        tips[1]['branchlen'] = 0;
+        assert_equal (tips[1], shortTip)
 
 if __name__ == '__main__':
     GetChainTipsTest ().main ()