add tests for block filter in get_head

test_libs/pyspec/eth2spec/test/fork_choice/test_get_head.py

@@ -1,7 +1,12 @@
 from eth2spec.test.context import with_all_phases, spec_state_test
 from eth2spec.test.helpers.attestations import get_valid_attestation
 from eth2spec.test.helpers.block import build_empty_block_for_next_slot
-from eth2spec.test.helpers.state import state_transition_and_sign_block
+from eth2spec.test.helpers.state import (
+    next_epoch,
+    next_epoch_with_attestations,
+    state_transition_and_sign_block,
+)
+from eth2spec.utils.ssz.ssz_impl import signing_root
 
 
 def add_block_to_store(spec, store, block):
@@ -112,3 +117,76 @@ def test_shorter_chain_but_heavier_weight(spec, state):
     add_attestation_to_store(spec, store, short_attestation)
 
     assert spec.get_head(store) == spec.signing_root(short_block)
+
+
+@with_all_phases
+@spec_state_test
+def test_filtered_block_tree(spec, state):
+    genesis_state = state.copy()
+
+    # transition state past initial couple of epochs
+    next_epoch(spec, state)
+    next_epoch(spec, state)
+
+    # Initialization
+    store = spec.get_genesis_store(genesis_state)
+    genesis_block = spec.BeaconBlock(state_root=genesis_state.hash_tree_root())
+    assert spec.get_head(store) == spec.signing_root(genesis_block)
+
+    # fill in attestations for entire epoch, justifying the recent epoch
+    prev_state, blocks, state = next_epoch_with_attestations(spec, state, True, False)
+    attestations = [attestation for block in blocks for attestation in block.body.attestations]
+    assert state.current_justified_checkpoint.epoch > prev_state.current_justified_checkpoint.epoch
+
+    # tick time forward and add blocks and attestations to store
+    current_time = state.slot * spec.SECONDS_PER_SLOT + store.genesis_time
+    spec.on_tick(store, current_time)
+    for block in blocks:
+        spec.on_block(store, block)
+    for attestation in attestations:
+        spec.on_attestation(store, attestation)
+
+    assert store.justified_checkpoint == state.current_justified_checkpoint
+
+    # the last block in the branch should be the head
+    expected_head_root = signing_root(blocks[-1])
+    assert spec.get_head(store) == expected_head_root
+
+    #
+    # create branch containing the justified block but not containing enough on
+    # chain votes to justify that block
+    #
+
+    # build a chain without attestations off of previous justified block
+    non_viable_state = store.block_states[store.justified_checkpoint.root].copy()
+
+    # ensure that next wave of votes are for future epoch
+    next_epoch(spec, non_viable_state)
+    next_epoch(spec, non_viable_state)
+    next_epoch(spec, non_viable_state)
+    assert spec.get_current_epoch(non_viable_state) > store.justified_checkpoint.epoch
+
+    # create rogue block that will be attested to in this non-viable branch
+    rogue_block = build_empty_block_for_next_slot(spec, non_viable_state, True)
+    state_transition_and_sign_block(spec, non_viable_state, rogue_block)
+
+    # create an epoch's worth of attestations for the rogue block
+    next_epoch(spec, non_viable_state)
+    attestations = []
+    for i in range(spec.SLOTS_PER_EPOCH):
+        slot = rogue_block.slot + i
+        for index in range(spec.get_committee_count_at_slot(non_viable_state, slot)):
+            attestation = get_valid_attestation(spec, non_viable_state, rogue_block.slot + i, index)
+            attestations.append(attestation)
+
+    # tick time forward to be able to include up to the latest attestation
+    current_time = (attestations[-1].data.slot + 1) * spec.SECONDS_PER_SLOT + store.genesis_time
+    spec.on_tick(store, current_time)
+
+    # include rogue block and associated attestations in the store
+    spec.on_block(store, rogue_block)
+    for attestation in attestations:
+        spec.on_attestation(store, attestation)
+
+    # ensure that get_head still returns the head from the previous branch
+    assert spec.get_head(store) == expected_head_root