enhance finality testing -- case 1, 2, 4

specs/core/0_beacon-chain.md

@@ -1697,18 +1697,22 @@ def process_justification_and_finalization(state: BeaconState) -> None:
     current_epoch = get_current_epoch(state)
     # The 2nd/3rd/4th most recent epochs are justified, the 2nd using the 4th as source
     if (bitfield >> 1) % 8 == 0b111 and old_previous_justified_epoch == current_epoch - 3:
+        print("rule 1")
         state.finalized_epoch = old_previous_justified_epoch
         state.finalized_root = get_block_root(state, get_epoch_start_slot(state.finalized_epoch))
     # The 2nd/3rd most recent epochs are justified, the 2nd using the 3rd as source
     if (bitfield >> 1) % 4 == 0b11 and old_previous_justified_epoch == current_epoch - 2:
+        print("rule 2")
         state.finalized_epoch = old_previous_justified_epoch
         state.finalized_root = get_block_root(state, get_epoch_start_slot(state.finalized_epoch))
     # The 1st/2nd/3rd most recent epochs are justified, the 1st using the 3rd as source
     if (bitfield >> 0) % 8 == 0b111 and old_current_justified_epoch == current_epoch - 2:
+        print("rule 3")
         state.finalized_epoch = old_current_justified_epoch
         state.finalized_root = get_block_root(state, get_epoch_start_slot(state.finalized_epoch))
     # The 1st/2nd most recent epochs are justified, the 1st using the 2nd as source
     if (bitfield >> 0) % 4 == 0b11 and old_current_justified_epoch == current_epoch - 1:
+        print("rule 4")
         state.finalized_epoch = old_current_justified_epoch
         state.finalized_root = get_block_root(state, get_epoch_start_slot(state.finalized_epoch))
 ```

test_libs/pyspec/tests/helpers.py

@@ -155,7 +155,6 @@ def build_attestation_data(state, slot, shard):
 
     current_epoch_start_slot = get_epoch_start_slot(get_current_epoch(state))
     if slot < current_epoch_start_slot:
-        print(slot)
         epoch_boundary_root = get_block_root(state, get_epoch_start_slot(get_previous_epoch(state)))
     elif slot == current_epoch_start_slot:
         epoch_boundary_root = block_root

test_libs/pyspec/tests/test_finality.py

@@ -0,0 +1,156 @@
+from copy import deepcopy
+
+import pytest
+
+import eth2spec.phase0.spec as spec
+
+from eth2spec.phase0.state_transition import (
+    state_transition,
+)
+from .helpers import (
+    build_empty_block_for_next_slot,
+    fill_aggregate_attestation,
+    get_current_epoch,
+    get_epoch_start_slot,
+    get_valid_attestation,
+    next_epoch,
+)
+
+# mark entire file as 'state'
+pytestmark = pytest.mark.state
+
+
+def check_finality(state,
+                   prev_state,
+                   current_justified_changed,
+                   previous_justified_changed,
+                   finalized_changed):
+    if current_justified_changed:
+        assert state.current_justified_epoch > prev_state.current_justified_epoch
+        assert state.current_justified_root != prev_state.current_justified_root
+    else:
+        assert state.current_justified_epoch == prev_state.current_justified_epoch
+        assert state.current_justified_root == prev_state.current_justified_root
+
+    if previous_justified_changed:
+        assert state.previous_justified_epoch > prev_state.previous_justified_epoch
+        assert state.previous_justified_root != prev_state.previous_justified_root
+    else:
+        assert state.previous_justified_epoch == prev_state.previous_justified_epoch
+        assert state.previous_justified_root == prev_state.previous_justified_root
+
+    if finalized_changed:
+        assert state.finalized_epoch > prev_state.finalized_epoch
+        assert state.finalized_root != prev_state.finalized_root
+    else:
+        assert state.finalized_epoch == prev_state.finalized_epoch
+        assert state.finalized_root == prev_state.finalized_root
+
+
+def test_finality_from_genesis_rule_4(state):
+    test_state = deepcopy(state)
+
+    blocks = []
+    for epoch in range(6):
+        old_current_justified_epoch = test_state.current_justified_epoch
+        old_current_justified_root = test_state.current_justified_root
+        for slot in range(spec.SLOTS_PER_EPOCH):
+            attestation = None
+            slot_to_attest = test_state.slot - spec.MIN_ATTESTATION_INCLUSION_DELAY + 1
+            if slot_to_attest >= spec.GENESIS_SLOT:
+                attestation = get_valid_attestation(test_state, slot_to_attest)
+                fill_aggregate_attestation(test_state, attestation)
+            block = build_empty_block_for_next_slot(test_state)
+            if attestation:
+                block.body.attestations.append(attestation)
+            state_transition(test_state, block)
+            blocks.append(block)
+
+        if epoch == 0:
+            check_finality(test_state, state, False, False, False)
+        elif epoch == 1:
+            check_finality(test_state, state, False, False, False)
+        elif epoch == 2:
+            check_finality(test_state, state, True, False, False)
+        elif epoch >= 3:
+            # rule 4 of finaliy
+            check_finality(test_state, state, True, True, True)
+            assert test_state.finalized_epoch == old_current_justified_epoch
+            assert test_state.finalized_root == old_current_justified_root
+
+    return state, blocks, test_state
+
+
+def test_finality_rule_1(state):
+    # get past first two epochs that finality does not run on
+    next_epoch(state)
+    next_epoch(state)
+
+    test_state = deepcopy(state)
+
+    blocks = []
+    for epoch in range(3):
+        old_previous_justified_epoch = test_state.previous_justified_epoch
+        old_previous_justified_root = test_state.previous_justified_root
+        for slot in range(spec.SLOTS_PER_EPOCH):
+            slot_to_attest = test_state.slot - spec.SLOTS_PER_EPOCH + 1
+            attestation = get_valid_attestation(test_state, slot_to_attest)
+            fill_aggregate_attestation(test_state, attestation)
+            block = build_empty_block_for_next_slot(test_state)
+            block.body.attestations.append(attestation)
+            state_transition(test_state, block)
+
+            assert len(test_state.previous_epoch_attestations) >= 0
+            assert len(test_state.current_epoch_attestations) == 0
+
+            blocks.append(block)
+
+        if epoch == 0:
+            check_finality(test_state, state, True, False, False)
+        elif epoch == 1:
+            check_finality(test_state, state, True, True, False)
+        elif epoch == 2:
+            # finalized by rule 1
+            check_finality(test_state, state, True, True, True)
+            assert test_state.finalized_epoch == old_previous_justified_epoch
+            assert test_state.finalized_root == old_previous_justified_root
+
+
+def test_finality_rule_2(state):
+    # get past first two epochs that finality does not run on
+    next_epoch(state)
+    next_epoch(state)
+
+    test_state = deepcopy(state)
+
+    blocks = []
+    for epoch in range(3):
+        old_previous_justified_epoch = test_state.previous_justified_epoch
+        old_previous_justified_root = test_state.previous_justified_root
+        for slot in range(spec.SLOTS_PER_EPOCH):
+            attestation = None
+            if epoch == 0:
+                slot_to_attest = test_state.slot - spec.MIN_ATTESTATION_INCLUSION_DELAY + 1
+                if slot_to_attest >= get_epoch_start_slot(get_current_epoch(state)):
+                    attestation = get_valid_attestation(test_state, slot_to_attest)
+                    fill_aggregate_attestation(test_state, attestation)
+            if epoch == 2:
+                slot_to_attest = test_state.slot - spec.SLOTS_PER_EPOCH + 1
+                attestation = get_valid_attestation(test_state, slot_to_attest)
+                fill_aggregate_attestation(test_state, attestation)
+
+            block = build_empty_block_for_next_slot(test_state)
+            if attestation:
+                block.body.attestations.append(attestation)
+            state_transition(test_state, block)
+            blocks.append(block)
+
+        if epoch == 0:
+            check_finality(test_state, state, True, False, False)
+        elif epoch == 1:
+            check_finality(test_state, state, True, True, False)
+        elif epoch == 2:
+            # finalized by rule 2
+            check_finality(test_state, state, True, True, True)
+            assert test_state.finalized_epoch == old_previous_justified_epoch
+            assert test_state.finalized_root == old_previous_justified_root

test_libs/pyspec/tests/test_sanity.py

@@ -145,33 +145,6 @@ def test_empty_epoch_transition_not_finalizing(state):
     return state, [block], test_state
 
 
-def test_full_attestations_finalizing(state):
-    test_state = deepcopy(state)
-
-    for slot in range(spec.MIN_ATTESTATION_INCLUSION_DELAY):
-        next_slot(test_state)
-
-    for epoch in range(5):
-        for slot in range(spec.SLOTS_PER_EPOCH):
-            print(test_state.slot)
-            attestation = get_valid_attestation(test_state, test_state.slot - spec.MIN_ATTESTATION_INCLUSION_DELAY)
-            fill_aggregate_attestation(test_state, attestation)
-            block = build_empty_block_for_next_slot(test_state)
-            block.body.attestations.append(attestation)
-            state_transition(test_state, block)
-
-        if epoch == 0:
-            check_finality(test_state, state, False, False, False)
-        elif epoch == 1:
-            check_finality(test_state, state, False, False, False)
-        elif epoch == 2:
-            check_finality(test_state, state, True, False, False)
-        elif epoch == 3:
-            check_finality(test_state, state, True, True, False)
-        elif epoch == 4:
-            check_finality(test_state, state, True, True, True)
-
-
 def test_proposer_slashing(state):
     test_state = deepcopy(state)
     proposer_slashing = get_valid_proposer_slashing(state)