Added `on_merge_block` client tests

specs/merge/fork-choice.md

@@ -70,8 +70,7 @@ def finalize_block(self: ExecutionEngine, block_hash: Hash32) -> bool:
 ### `PowBlock`
 
 ```python
-@dataclass
-class PowBlock(object):
+class PowBlock(Container):
     block_hash: Hash32
     parent_hash: Hash32
     total_difficulty: uint256

tests/core/pyspec/eth2spec/test/merge/fork_choice/test_on_merge_block.py

@@ -0,0 +1,162 @@
+from eth2spec.utils.ssz.ssz_typing import uint256
+from eth2spec.test.context import spec_state_test, with_phases, MERGE
+from eth2spec.test.helpers.block import (
+    build_empty_block_for_next_slot
+)
+from eth2spec.test.helpers.fork_choice import (
+    get_genesis_forkchoice_store_and_block,
+    on_tick_and_append_step,
+    tick_and_add_block,
+)
+from eth2spec.test.helpers.state import (
+    state_transition_and_sign_block,
+)
+from eth2spec.test.helpers.block import (
+    prepare_empty_pow_block
+)
+
+
+def with_pow_block_patch(spec, blocks, func):
+    def get_pow_block(hash: spec.Bytes32) -> spec.PowBlock:
+        for block in blocks:
+            if block.block_hash == hash:
+                return block
+        raise Exception("Block not found")
+    get_pow_block_backup = spec.get_pow_block
+    spec.get_pow_block = get_pow_block
+
+    class AtomicBoolean():
+        value = False
+    is_called = AtomicBoolean()
+
+    def wrap(flag: AtomicBoolean):
+        func()
+        flag.value = True
+
+    try:
+        wrap(is_called)
+    finally:
+        spec.get_pow_block = get_pow_block_backup
+    assert is_called.value
+
+
+@with_phases([MERGE])
+@spec_state_test
+def test_all_valid(spec, state):
+    test_steps = []
+    # Initialization
+    store, anchor_block = get_genesis_forkchoice_store_and_block(spec, state)
+    yield 'anchor_state', state
+    yield 'anchor_block', anchor_block
+    current_time = state.slot * spec.config.SECONDS_PER_SLOT + store.genesis_time
+    on_tick_and_append_step(spec, store, current_time, test_steps)
+    assert store.time == current_time
+
+    parent_block = prepare_empty_pow_block(spec)
+    parent_block.total_difficulty = spec.config.TERMINAL_TOTAL_DIFFICULTY - uint256(1)
+    block = prepare_empty_pow_block(spec)
+    block.parent_hash = parent_block.block_hash
+    block.total_difficulty = spec.config.TERMINAL_TOTAL_DIFFICULTY
+    pow_blocks = [block, parent_block]
+    yield 'pow_blocks', pow_blocks
+
+    def run_func():
+        block = build_empty_block_for_next_slot(spec, state)
+        signed_block = state_transition_and_sign_block(spec, state, block)
+        yield from tick_and_add_block(spec, store, signed_block, test_steps)
+        # valid
+        assert spec.get_head(store) == signed_block.message.hash_tree_root()
+
+    with_pow_block_patch(spec, pow_blocks, run_func)
+    yield 'steps', test_steps
+
+
+@with_phases([MERGE])
+@spec_state_test
+def test_block_lookup_failed(spec, state):
+    test_steps = []
+    # Initialization
+    store, anchor_block = get_genesis_forkchoice_store_and_block(spec, state)
+    yield 'anchor_state', state
+    yield 'anchor_block', anchor_block
+    current_time = state.slot * spec.config.SECONDS_PER_SLOT + store.genesis_time
+    on_tick_and_append_step(spec, store, current_time, test_steps)
+    assert store.time == current_time
+
+
+    parent_block = prepare_empty_pow_block(spec)
+    parent_block.total_difficulty = spec.config.TERMINAL_TOTAL_DIFFICULTY - uint256(1)
+    pow_blocks = [parent_block]
+    yield 'pow_blocks', pow_blocks
+
+    def run_func():
+        block = build_empty_block_for_next_slot(spec, state)
+        signed_block = state_transition_and_sign_block(spec, state, block)
+        yield from tick_and_add_block(spec, store, signed_block, test_steps)
+        # invalid
+        assert spec.get_head(store) == anchor_block.state_root
+
+    with_pow_block_patch(spec, pow_blocks, run_func)
+    yield 'steps', test_steps
+
+
+@with_phases([MERGE])
+@spec_state_test
+def test_too_early_for_merge(spec, state):
+    test_steps = []
+    # Initialization
+    store, anchor_block = get_genesis_forkchoice_store_and_block(spec, state)
+    yield 'anchor_state', state
+    yield 'anchor_block', anchor_block
+    current_time = state.slot * spec.config.SECONDS_PER_SLOT + store.genesis_time
+    on_tick_and_append_step(spec, store, current_time, test_steps)
+    assert store.time == current_time
+
+    parent_block = prepare_empty_pow_block(spec)
+    parent_block.total_difficulty = spec.config.TERMINAL_TOTAL_DIFFICULTY - uint256(2)
+    block = prepare_empty_pow_block(spec)
+    block.parent_hash = parent_block.block_hash
+    block.total_difficulty = spec.config.TERMINAL_TOTAL_DIFFICULTY - uint256(1)
+    pow_blocks = [block, parent_block]
+    yield 'pow_blocks', pow_blocks
+
+    def run_func():
+        block = build_empty_block_for_next_slot(spec, state)
+        signed_block = state_transition_and_sign_block(spec, state, block)
+        yield from tick_and_add_block(spec, store, signed_block, test_steps)
+        # invalid
+        assert spec.get_head(store) == anchor_block.state_root
+
+    with_pow_block_patch(spec, pow_blocks, run_func)
+    yield 'steps', test_steps
+
+
+@with_phases([MERGE])
+@spec_state_test
+def test_too_late_for_merge(spec, state):
+    test_steps = []
+    # Initialization
+    store, anchor_block = get_genesis_forkchoice_store_and_block(spec, state)
+    yield 'anchor_state', state
+    yield 'anchor_block', anchor_block
+    current_time = state.slot * spec.config.SECONDS_PER_SLOT + store.genesis_time
+    on_tick_and_append_step(spec, store, current_time, test_steps)
+    assert store.time == current_time
+
+    parent_block = prepare_empty_pow_block(spec)
+    parent_block.total_difficulty = spec.config.TERMINAL_TOTAL_DIFFICULTY
+    block = prepare_empty_pow_block(spec)
+    block.parent_hash = parent_block.block_hash
+    block.total_difficulty = spec.config.TERMINAL_TOTAL_DIFFICULTY + uint256(1)
+    pow_blocks = [block, parent_block]
+    yield 'pow_blocks', pow_blocks
+
+    def run_func():
+        block = build_empty_block_for_next_slot(spec, state)
+        signed_block = state_transition_and_sign_block(spec, state, block)
+        yield from tick_and_add_block(spec, store, signed_block, test_steps)
+        # invalid
+        assert spec.get_head(store) == anchor_block.state_root
+
+    with_pow_block_patch(spec, pow_blocks, run_func)
+    yield 'steps', test_steps

tests/generators/fork_choice/main.py

@@ -9,8 +9,14 @@ if __name__ == "__main__":
     ]}
     # No additional Altair specific finality tests, yet.
     altair_mods = phase_0_mods
-    # No specific Merge tests yet.
-    merge_mods = altair_mods
+    # For merge `on_merge_block` test kind added with `pow_block_N.ssz` files with several
+    # PowBlock's which should be resolved by `get_pow_block(hash: Hash32) -> PowBlock` function
+    merge_mods = {
+        **{key: 'eth2spec.test.merge.fork_choice.test_' + key for key in [
+            'on_merge_block',
+        ]},
+        **altair_mods,
+    }
 
     all_mods = {
         PHASE0: phase_0_mods,