Fix spec typo and add test_prepare_execution_payload unit tests

specs/merge/validator.md

@@ -125,7 +125,7 @@ def prepare_execution_payload(state: BeaconState,
                               execution_engine: ExecutionEngine) -> Optional[PayloadId]:
     if not is_merge_complete(state):
         is_terminal_block_hash_set = TERMINAL_BLOCK_HASH != Hash32()
-        is_activation_epoch_reached = get_current_epoch(state.slot) >= TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH
+        is_activation_epoch_reached = get_current_epoch(state) >= TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH
         if is_terminal_block_hash_set and not is_activation_epoch_reached:
             # Terminal block hash is set but activation epoch is not yet reached, no prepare payload call is needed
             return None

tests/core/pyspec/eth2spec/test/merge/unittests/validator/test_validator.py

@@ -1,3 +1,5 @@
+from copy import deepcopy
+
 from eth2spec.test.helpers.pow_block import (
     prepare_random_pow_chain,
 )
@@ -62,3 +64,99 @@ def test_get_pow_block_at_terminal_total_difficulty(spec, state):
             assert pow_block is None
         else:
             raise Exception('Something is wrong')
+
+
+SAMPLE_PAYLOAD_ID = b'\x12' * 8
+# ('is_merge_complete', 'is_terminal_block_hash_set', 'is_activation_epoch_reached',
+# 'terminal_pow_block_is_none', 'result_payload_id')
+prepare_execution_payload_expected_results = [
+    (False, False, False, False, SAMPLE_PAYLOAD_ID),
+    (False, False, False, True, None),
+    (False, False, True, False, SAMPLE_PAYLOAD_ID),
+    (False, False, True, True, None),
+    (False, True, False, False, None),
+    (False, True, False, True, None),
+    (False, True, True, False, SAMPLE_PAYLOAD_ID),
+    (False, True, True, True, None),
+    (True, False, False, False, SAMPLE_PAYLOAD_ID),
+    (True, False, False, True, SAMPLE_PAYLOAD_ID),
+    (True, False, True, False, SAMPLE_PAYLOAD_ID),
+    (True, False, True, True, SAMPLE_PAYLOAD_ID),
+    (True, True, False, False, SAMPLE_PAYLOAD_ID),
+    (True, True, False, True, SAMPLE_PAYLOAD_ID),
+    (True, True, True, False, SAMPLE_PAYLOAD_ID),
+    (True, True, True, True, SAMPLE_PAYLOAD_ID),
+]
+
+
+@with_merge_and_later
+@spec_state_test
+def test_prepare_execution_payload(spec, state):
+    for result in prepare_execution_payload_expected_results:
+        (
+            is_merge_complete,
+            is_terminal_block_hash_set,
+            is_activation_epoch_reached,
+            terminal_pow_block_is_none,
+            result_payload_id,
+        ) = result
+
+        # 1. Handle `is_merge_complete`
+        if is_merge_complete:
+            state.latest_execution_payload_header = spec.ExecutionPayloadHeader(random=b'\x12' * 32)
+        else:
+            state.latest_execution_payload_header = spec.ExecutionPayloadHeader()
+
+        # 2. `is_terminal_block_hash_set` and `is_activation_epoch_reached` require mocking configs in runtime
+        config_overrides = {}
+        _mock_terminal_block_hash = b'\x34' * 32
+        if is_terminal_block_hash_set:
+            config_overrides['TERMINAL_BLOCK_HASH'] = _mock_terminal_block_hash
+        else:
+            config_overrides['TERMINAL_BLOCK_HASH'] = spec.Hash32()
+
+        # Default `TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH` is too big and too close to overflow
+        _mock_terminal_block_hash_activation_epoch = 3
+        config_overrides['TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH'] = _mock_terminal_block_hash_activation_epoch
+        if is_activation_epoch_reached:
+            state.slot = _mock_terminal_block_hash_activation_epoch * spec.SLOTS_PER_EPOCH
+        else:
+            state.slot = (_mock_terminal_block_hash_activation_epoch - 1) * spec.SLOTS_PER_EPOCH
+
+        # Logic from `with_config_overrides`
+        old_config = spec.config
+        tmp_config = deepcopy(old_config._asdict())
+        tmp_config.update(config_overrides)
+        config_types = spec.Configuration.__annotations__
+        test_config = {k: config_types[k](v) for k, v in tmp_config.items()}
+        spec.config = spec.Configuration(**test_config)
+
+        # 3. Handle `terminal_pow_block_is_none`
+        pow_chain = prepare_random_pow_chain(spec, 2)
+        if terminal_pow_block_is_none:
+            pow_chain.head().total_difficulty = spec.config.TERMINAL_TOTAL_DIFFICULTY - 1
+        else:
+            if is_terminal_block_hash_set:
+                pow_chain.head().block_hash = _mock_terminal_block_hash
+            pow_chain.head().total_difficulty = spec.config.TERMINAL_TOTAL_DIFFICULTY
+
+        # Dummy arguments
+        finalized_block_hash = b'\x56' * 32
+        suggested_fee_recipient = b'\x78' * 20
+
+        # Mock execution_engine
+        class TestEngine(spec.NoopExecutionEngine):
+            def notify_forkchoice_updated(self, parent_hash, finalized_block_hash, payload_attributes) -> bool:
+                return SAMPLE_PAYLOAD_ID
+
+        payload_id = spec.prepare_execution_payload(
+            state=state,
+            pow_chain=pow_chain.to_dict(),
+            finalized_block_hash=finalized_block_hash,
+            suggested_fee_recipient=suggested_fee_recipient,
+            execution_engine=TestEngine(),
+        )
+        assert payload_id == result_payload_id
+
+        # Restore config
+        spec.config = old_config