test: add coverage to rpc_blockchain.py

Included a test that checks the functionality of setting
the first param of getnetworkhashps to negative value returns
the average network hashes per second from the last difficulty change.

Co-authored-by: ismaelsadeeq <[email protected]>

Author: kevkevinpal

test/functional/rpc_blockchain.py

@@ -58,6 +58,7 @@
 TIME_RANGE_MTP = TIME_GENESIS_BLOCK + (HEIGHT - 6) * TIME_RANGE_STEP
 TIME_RANGE_TIP = TIME_GENESIS_BLOCK + (HEIGHT - 1) * TIME_RANGE_STEP
 TIME_RANGE_END = TIME_GENESIS_BLOCK + HEIGHT * TIME_RANGE_STEP
+DIFFICULTY_ADJUSTMENT_INTERVAL = 2016
 
 
 class BlockchainTest(BitcoinTestFramework):
@@ -451,6 +452,15 @@ def _test_getnetworkhashps(self):
         # This should be 2 hashes every 10 minutes or 1/300
         assert abs(hashes_per_second * 300 - 1) < 0.0001
 
+        # Test setting the first param of getnetworkhashps to negative value returns the average network
+        # hashes per second from the last difficulty change.
+        current_block_height = self.nodes[0].getmininginfo()['blocks']
+        blocks_since_last_diff_change = current_block_height % DIFFICULTY_ADJUSTMENT_INTERVAL + 1
+        expected_hashes_per_second_since_diff_change = self.nodes[0].getnetworkhashps(blocks_since_last_diff_change)
+
+        assert_equal(self.nodes[0].getnetworkhashps(-1), expected_hashes_per_second_since_diff_change)
+        assert_equal(self.nodes[0].getnetworkhashps(-2), expected_hashes_per_second_since_diff_change)
+
     def _test_stopatheight(self):
         self.log.info("Test stopping at height")
         assert_equal(self.nodes[0].getblockcount(), HEIGHT)