Add test for exited validators during inactivity leak

tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_inactivity_updates.py

@@ -3,10 +3,15 @@ from random import Random
 from eth2spec.test.context import spec_state_test, with_altair_and_later
 from eth2spec.test.helpers.inactivity_scores import randomize_inactivity_scores, zero_inactivity_scores
 from eth2spec.test.helpers.state import (
+    next_epoch,
     next_epoch_via_block,
     set_full_participation,
     set_empty_participation,
 )
+from eth2spec.test.helpers.voluntary_exits import (
+    exit_validators,
+    get_exited_validators
+)
 from eth2spec.test.helpers.epoch_processing import (
     run_epoch_processing_with
 )
@@ -266,3 +271,53 @@ def test_some_slashed_full_random_leaking(spec, state):
 
     # Check still in leak
     assert spec.is_in_inactivity_leak(state)
+
+
+@with_altair_and_later
+@spec_state_test
+@leaking()
+def test_some_exited_full_random_leaking(spec, state):
+    rng = Random(1102233)
+
+    exit_count = 3
+
+    # randomize ahead of time to check exited validators do not have
+    # mutations applied to their inactivity scores
+    randomize_inactivity_scores(spec, state, rng=rng)
+
+    assert not get_exited_validators(spec, state)
+    exited_indices = exit_validators(spec, state, exit_count, rng=rng)
+    assert not get_exited_validators(spec, state)
+
+    # advance the state to effect the exits
+    target_epoch = max(state.validators[index].exit_epoch for index in exited_indices)
+    # validators that have exited in the previous epoch or earlier will not
+    # have their inactivity scores modified, the test advances the state past this point
+    # to confirm this invariant:
+    previous_epoch = spec.get_previous_epoch(state)
+    for _ in range(target_epoch - previous_epoch):
+        next_epoch(spec, state)
+    assert len(get_exited_validators(spec, state)) == exit_count
+
+    previous_scores = state.inactivity_scores.copy()
+
+    yield from run_inactivity_scores_test(
+        spec, state,
+        randomize_previous_epoch_participation, rng=rng,
+    )
+
+    # ensure exited validators have their score "frozen" at exit
+    # but otherwise there was a change
+    some_changed = False
+    for index in range(len(state.validators)):
+        if index in exited_indices:
+            assert previous_scores[index] == state.inactivity_scores[index]
+        else:
+            previous_score = previous_scores[index]
+            current_score = state.inactivity_scores[index]
+            if previous_score != current_score:
+                some_changed = True
+    assert some_changed
+
+    # Check still in leak
+    assert spec.is_in_inactivity_leak(state)

tests/core/pyspec/eth2spec/test/helpers/voluntary_exits.py

@@ -1,3 +1,4 @@
+from random import Random
 from eth2spec.utils import bls
 from eth2spec.test.helpers.keys import privkeys
 
@@ -23,3 +24,21 @@ def sign_voluntary_exit(spec, state, voluntary_exit, privkey):
         message=voluntary_exit,
         signature=bls.Sign(privkey, signing_root)
     )
+
+
+#
+# Helpers for applying effects of a voluntary exit
+#
+def get_exited_validators(spec, state):
+    current_epoch = spec.get_current_epoch(state)
+    return [index for (index, validator) in enumerate(state.validators) if validator.exit_epoch <= current_epoch]
+
+
+def exit_validators(spec, state, validator_count, rng=None):
+    if rng is None:
+        rng = Random(1337)
+
+    indices = rng.sample(range(len(state.validators)), validator_count)
+    for index in indices:
+        spec.initiate_validator_exit(state, index)
+    return indices