Fix test_demo.py

1. Fix serenity validation type hinting
2. Fix test_demo.py arguments
3. Add more testcase for `test_get_shard_committees_at_slot`
4. Add more output message for `get_shard_committees_at_slot` and `get_block_root`

Author: hwwhww

eth/beacon/helpers.py

@@ -76,8 +76,14 @@ def _get_block_root(
     if state_slot > slot + latest_block_roots_length:
         raise ValueError(
             "state.slot (%s) should be less than or equal to "
-            "(slot + latest_block_roots_length) (%s)" %
-            (state_slot, slot + latest_block_roots_length)
+            "(slot + latest_block_roots_length) (%s), "
+            "where slot=%s, latest_block_roots_length=%s" %
+            (
+                state_slot,
+                slot + latest_block_roots_length,
+                slot,
+                latest_block_roots_length,
+            )
         )
     if slot >= state_slot:
         raise ValueError(
@@ -121,8 +127,15 @@ def _get_shard_committees_at_slot(
         )
     if slot >= earliest_slot_in_array + epoch_length * 2:
         raise ValueError(
-            "slot (%s) should be less than earliest_slot_in_array + epoch_length * 2 (%s)" %
-            (slot, earliest_slot_in_array + epoch_length * 2)
+            "slot (%s) should be less than "
+            "(earliest_slot_in_array + epoch_length * 2) (%s), "
+            "where earliest_slot_in_array=%s, epoch_length=%s" %
+            (
+                slot,
+                earliest_slot_in_array + epoch_length * 2,
+                earliest_slot_in_array,
+                epoch_length,
+            )
         )
 
     return shard_committees_at_slots[slot - earliest_slot_in_array]

eth/beacon/state_machines/forks/serenity/validation.py

@@ -5,7 +5,6 @@
     ValidationError,
 )
 import rlp
-from typing import Type
 
 from eth.constants import (
     ZERO_HASH32,
@@ -69,7 +68,7 @@ def validate_serenity_proposer_signature(state: BeaconState,
 #
 # Attestation validation
 #
-def validate_serenity_attestation(state: Type[BeaconState],
+def validate_serenity_attestation(state: BeaconState,
                                   attestation: Attestation,
                                   epoch_length: int,
                                   min_attestation_inclusion_delay: int,
@@ -238,7 +237,7 @@ def validate_serenity_attestation_shard_block_root(attestation_data: Attestation
         )
 
 
-def validate_serenity_attestation_aggregate_signature(state: Type[BeaconState],
+def validate_serenity_attestation_aggregate_signature(state: BeaconState,
                                                       attestation: Attestation,
                                                       epoch_length: int) -> None:
     """

tests/beacon/state_machines/test_demo.py

@@ -26,7 +26,7 @@
         'shard_count'
     ),
     [
-        (10, 2, 1, 2, 2)
+        (10, 10, 1, 2, 2)
     ]
 )
 def test_demo(base_db,
@@ -45,10 +45,7 @@ def test_demo(base_db,
 
     # Sign block
     beacon_proposer_index = get_beacon_proposer_index(
-        # TODO: use `state` when the bug of `get_shard_committees_at_slot` is fixed.
-        state.copy(
-            slot=state.slot + 2,
-        ),
+        state,
         block.slot,
         config.EPOCH_LENGTH,
     )

tests/beacon/test_helpers.py

@@ -183,6 +183,15 @@ def test_get_block_root(current_slot,
             64,
             True,
         ),
+        (
+            100,
+            64,
+            1,
+            128,
+            10,
+            1,
+            True,
+        ),
         # slot is too small
         (
             100,