Add some tests for getchaintxstats

1. Add a test for no parameters.
2. Add a test for the block's height = 1.
3. Add a test for nblocks is out of range.

test/functional/blockchain.py

@@ -56,6 +56,28 @@ class BlockchainTest(BitcoinTestFramework):
         # we have to round because of binary math
         assert_equal(round(chaintxstats['txrate'] * 600, 10), Decimal(1))
 
+        b1 = self.nodes[0].getblock(self.nodes[0].getblockhash(1))
+        b200 = self.nodes[0].getblock(self.nodes[0].getblockhash(200))
+        time_diff = b200['mediantime'] - b1['mediantime']
+
+        chaintxstats = self.nodes[0].getchaintxstats()
+        assert_equal(chaintxstats['time'], b200['time'])
+        assert_equal(chaintxstats['txcount'], 201)
+        assert_equal(chaintxstats['window_block_count'], 199)
+        assert_equal(chaintxstats['window_tx_count'], 199)
+        assert_equal(chaintxstats['window_interval'], time_diff)
+        assert_equal(round(chaintxstats['txrate'] * time_diff, 10), Decimal(199))
+
+        chaintxstats = self.nodes[0].getchaintxstats(blockhash=b1['hash'])
+        assert_equal(chaintxstats['time'], b1['time'])
+        assert_equal(chaintxstats['txcount'], 2)
+        assert_equal(chaintxstats['window_block_count'], 0)
+        assert('window_tx_count' not in chaintxstats)
+        assert('window_interval' not in chaintxstats)
+        assert('txrate' not in chaintxstats)
+
+        assert_raises_jsonrpc(-8, "Invalid block count: should be between 0 and the block's height - 1", self.nodes[0].getchaintxstats, 201)
+
     def _test_gettxoutsetinfo(self):
         node = self.nodes[0]
         res = node.gettxoutsetinfo()