Double fetch size of mempool.

Set testnet genesis hash.

lib/coins.py

@@ -278,6 +278,8 @@ class BitcoinTestnet(Bitcoin):
     P2PKH_VERBYTE = 0x6f
     P2SH_VERBYTE = 0xc4
     WIF_BYTE = 0xef
+    GENESIS_HASH=(b'000000000933ea01ad0ee984209779ba'
+                  b'aec3ced90fa3f408719526f8d77f4943')
     REORG_LIMIT = 2000
     TX_COUNT = 12242438
     TX_COUNT_HEIGHT = 1035428

server/mempool.py

@@ -89,7 +89,7 @@ class MemPool(util.LoggedClass):
         unprocessed = {}
         unfetched = set()
         txs = self.txs
-        fetch_size = 400
+        fetch_size = 800
         process_some = self.async_process_some(unfetched, fetch_size // 2)
 
         await self.daemon.mempool_refresh_event.wait()