fix: reconcile differences with main after rebase + cleanup impl

- Reconcile differences with ``main`` after rebase.
- Clean up the implementation of the test fixtures + remove clunky
  builder for now.

Author: fselmo

packages/testing/src/consensus_testing/__init__.py

@@ -4,7 +4,9 @@
 
 from framework.base_types import CamelModel
 
-from .builders import BlockBuilder
+from . import forks
+from .block_spec import BlockSpec
+from .genesis import generate_pre_state
 from .test_fixtures import (
     BaseConsensusFixture,
     ForkChoiceTest,
@@ -25,7 +27,9 @@
 
 __all__ = [
     # Public API
-    "BlockBuilder",
+    "BlockSpec",
+    "forks",
+    "generate_pre_state",
     # Base types
     "CamelModel",
     # Fixture classes

packages/testing/src/consensus_testing/block_spec.py

@@ -0,0 +1,56 @@
+"""Lightweight block specification for test definitions."""
+
+from pydantic import BaseModel
+
+from lean_spec.subspecs.containers.block import BlockBody
+from lean_spec.subspecs.containers.slot import Slot
+from lean_spec.types import Bytes32, ValidatorIndex
+
+
+class BlockSpec(BaseModel):
+    """
+    Block specification for test definitions.
+
+    Contains the same fields as Block, but all optional except slot.
+    The framework fills in any missing fields automatically.
+
+    This matches the pattern from execution-specs where Block(...) is a spec
+    that the framework builds into a full block.
+
+    Usage:
+    - Simple: BlockSpec(slot=Slot(1)) - framework computes everything
+    - Custom: BlockSpec(slot=Slot(1), proposer_index=ValidatorIndex(5)) - override specific fields
+    - Invalid: BlockSpec(slot=Slot(1), state_root=Bytes32.zero()) - test invalid blocks
+    """
+
+    slot: Slot
+    """The slot for this block (required)."""
+
+    proposer_index: ValidatorIndex | None = None
+    """
+    The proposer index for this block.
+
+    If None, framework selects using round-robin based on slot and num_validators.
+    """
+
+    parent_root: Bytes32 | None = None
+    """
+    The root of the parent block.
+
+    If None, framework computes from state.latest_block_header.
+    """
+
+    state_root: Bytes32 | None = None
+    """
+    The state root after applying this block.
+
+    If None, framework computes via state_transition dry-run.
+    """
+
+    body: BlockBody | None = None
+    """
+    The block body containing attestations.
+
+    If None, framework creates empty body for state transition tests,
+    or collects attestations for fork choice tests.
+    """

packages/testing/src/consensus_testing/builders.py

@@ -0,0 +1,30 @@
+"""Consensus layer pre-state generation."""
+
+from typing import Any
+
+from lean_spec.subspecs.containers.state import State, Validators
+from lean_spec.subspecs.containers.validator import Validator
+from lean_spec.types import Bytes52, Uint64
+
+
+def generate_pre_state(**kwargs: Any) -> State:
+    """
+    Generate a default pre-state for consensus tests.
+
+    Args:
+        **kwargs: Optional keyword arguments:
+            - genesis_time: The genesis timestamp (defaults to Uint64(0)).
+            - validators: Validators list (defaults to 4 validators with dummy pubkeys).
+
+    Returns:
+        State: A properly initialized consensus state.
+    """
+    genesis_time = kwargs.get("genesis_time", Uint64(0))
+
+    # If validators not provided, create a default set of 4 validators with dummy pubkeys
+    if "validators" not in kwargs:
+        validators = Validators(data=[Validator(pubkey=Bytes52.zero()) for _ in range(4)])
+    else:
+        validators = kwargs["validators"]
+
+    return State.generate_genesis(genesis_time=genesis_time, validators=validators)