Fix StateMachine initialization

Author: hwwhww

eth/beacon/helpers.py

@@ -1,4 +1,3 @@
-import functools
 from itertools import (
     repeat,
 )

eth/beacon/state_machines/base.py

@@ -85,10 +85,10 @@ def __init__(self, chaindb: BaseBeaconChainDB, block: BaseBeaconBlock=None) -> N
         self.chaindb = chaindb
         if block is None:
             # Build a child block of current head
-            head = self.chaindb.get_canonical_head()
-            self.block = self.get_block_class()(*block).copy(
-                slot_number=head.slot_number + 1,
-                parent_hash=head.hash,
+            head_block = self.chaindb.get_canonical_head()
+            self.block = self.get_block_class()(*head_block).copy(
+                slot_number=head_block.slot_number + 1,
+                parent_hash=head_block.hash,
             )
         else:
             self.block = self.get_block_class()(*block)

tests/beacon/state_machines/test_state_machines.py

@@ -9,6 +9,20 @@
 )
 
 
+def test_state_machine_canonical(initial_chaindb,
+                                 genesis_block,
+                                 genesis_crystallized_state,
+                                 genesis_active_state):
+    chaindb = initial_chaindb
+    sm = SerenityStateMachine(chaindb)
+    assert sm.block == genesis_block.copy(
+        slot_number=genesis_block.slot_number + 1,
+        parent_hash=genesis_block.hash
+    )
+    assert sm.crystallized_state == genesis_crystallized_state
+    assert sm.active_state == genesis_active_state
+
+
 def test_state_machine(initial_chaindb,
                        genesis_block,
                        genesis_crystallized_state):