chore(test-specs): fix fork transition tests (ethereum#2065)

* chore(test-specs): fix fork transition tests

* fix(test-forks): don't collect BPO tests w/ unchanged params on transition

- Use `fork.excess_blob_gas_calculator` to account for fork-specific
  blob gas calculations.

* refactor(test-forks): clearer definitions for transition forks

---------

Co-authored-by: fselmo <fselmo2@gmail.com>

Author: spencer-tb

packages/testing/src/execution_testing/cli/pytest_commands/plugins/forks/forks.py

@@ -1181,6 +1181,24 @@ def add_fork_covariant_parameters(
                 fp for fp in fork_parametrizers if fp.fork >= param_min_fork
             ]
 
+    # Filter out forks where blob params don't change for valid_for_bpo_forks
+    if list(metafunc.definition.iter_markers(name="valid_for_bpo_forks")):
+        filtered_forks = [
+            fp.fork
+            for fp in fork_parametrizers
+            if not blob_params_changed_at_transition(fp.fork)
+        ]
+        if filtered_forks:
+            logger.debug(
+                f"Skipping {metafunc.function.__name__} for forks with "
+                f"unchanged blob params: {[f.name() for f in filtered_forks]}"
+            )
+        fork_parametrizers[:] = [
+            fp
+            for fp in fork_parametrizers
+            if blob_params_changed_at_transition(fp.fork)
+        ]
+
     for covariant_descriptor in fork_covariant_decorators:
         if list(
             metafunc.definition.iter_markers(covariant_descriptor.marker_name)
@@ -1272,6 +1290,48 @@ def parametrize_fork(
     )
 
 
+def blob_params_changed_at_transition(fork: Fork) -> bool:
+    """
+    Check if BPO-relevant blob parameters change at a fork transition.
+
+    For transition forks, compares the 3 blob parameters that BPO forks modify
+    between the from_fork and to_fork:
+
+    - target_blobs_per_block
+    - max_blobs_per_block
+    - blob_base_fee_update_fraction
+
+    Returns True if any parameter changed, False otherwise.
+
+    For non-transition forks, returns True (no filtering needed).
+    """
+    # Check if this is a transition fork
+    if not hasattr(fork, "transitions_from") or not hasattr(
+        fork, "transitions_to"
+    ):
+        return True
+
+    from_fork = fork.transitions_from()
+    to_fork = fork.transitions_to()
+
+    # Compare the 3 blob parameters that BPO forks modify
+    bpo_blob_params = [
+        "target_blobs_per_block",
+        "max_blobs_per_block",
+        "blob_base_fee_update_fraction",
+    ]
+
+    for param in bpo_blob_params:
+        from_method = getattr(from_fork, param, None)
+        to_method = getattr(to_fork, param, None)
+        if from_method is None or to_method is None:
+            continue
+        if from_method() != to_method():
+            return True
+
+    return False
+
+
 def pytest_collection_modifyitems(
     config: pytest.Config, items: List[pytest.Item]
 ) -> None:

packages/testing/src/execution_testing/forks/forks/transition.py

@@ -6,6 +6,7 @@
     BPO2,
     BPO3,
     BPO4,
+    Amsterdam,
     Berlin,
     Cancun,
     London,
@@ -66,6 +67,17 @@ class BPO1ToBPO2AtTime15k(BPO1):
     pass
 
 
+@transition_fork(to_fork=Amsterdam, at_timestamp=15_000)
+class BPO2ToAmsterdamAtTime15k(BPO2):
+    """BPO2 to Amsterdam transition at Timestamp 15k."""
+
+    # TODO: We may need to adjust which BPO Amsterdam inherits from as the
+    #  related Amsterdam specs change over time, and before Amsterdam is
+    #  live on mainnet.
+
+    pass
+
+
 @transition_fork(to_fork=BPO3, at_timestamp=15_000)
 class BPO2ToBPO3AtTime15k(BPO2):
     """BPO2 to BPO3 transition at Timestamp 15k."""

tests/cancun/eip4844_blobs/test_excess_blob_gas_fork_transition.py

@@ -158,24 +158,36 @@ def pre_fork_blocks(
 
 
 @pytest.fixture
-def pre_fork_excess_blobs(
+def pre_fork_excess_blob_gas(
     fork: Fork,
     pre_fork_blobs_per_block: int,
     pre_fork_blocks: List[Block],
+    block_base_fee_per_gas: int,
 ) -> int:
     """
-    Return the cumulative excess blobs up until the fork given the
-    pre_fork_blobs_per_block and the target blobs in the fork prior.
+    Return the cumulative excess blob gas up until the fork.
+
+    Calculates the expected excess blob gas by iterating through pre-fork
+    blocks using the fork's calculator, which handles EIP-7918 reserve price
+    for >=Osaka.
     """
     if not fork.supports_blobs(timestamp=0):
         return 0
 
-    target_blobs = fork.target_blobs_per_block(timestamp=0)
-    if pre_fork_blobs_per_block > target_blobs:
-        return (pre_fork_blobs_per_block - target_blobs) * (
-            len(pre_fork_blocks) - 1
+    calc_excess_blob_gas = fork.excess_blob_gas_calculator(timestamp=0)
+    excess_blob_gas = 0
+
+    # Calculate excess accumulation for each pre-fork block
+    # First block is built on genesis which has 0 blobs
+    for i in range(len(pre_fork_blocks)):
+        parent_blob_count = 0 if i == 0 else pre_fork_blobs_per_block
+        excess_blob_gas = calc_excess_blob_gas(
+            parent_excess_blob_gas=excess_blob_gas,
+            parent_blob_count=parent_blob_count,
+            parent_base_fee_per_gas=block_base_fee_per_gas,
         )
-    return 0
+
+    return excess_blob_gas
 
 
 @pytest.fixture
@@ -204,7 +216,7 @@ def gas_spender_account(pre: Alloc) -> Address:  # noqa: D103
 @pytest.fixture
 def fork_block_excess_blob_gas(
     fork: Fork,
-    pre_fork_excess_blobs: int,
+    pre_fork_excess_blob_gas: int,
     pre_fork_blobs_per_block: int,
     block_base_fee_per_gas: int,
 ) -> int:
@@ -215,7 +227,7 @@ def fork_block_excess_blob_gas(
         timestamp=FORK_TIMESTAMP
     )
     return calc_excess_blob_gas_post_fork(
-        parent_excess_blobs=pre_fork_excess_blobs,
+        parent_excess_blob_gas=pre_fork_excess_blob_gas,
         parent_blob_count=pre_fork_blobs_per_block,
         parent_base_fee_per_gas=block_base_fee_per_gas,
     )
@@ -463,6 +475,7 @@ def test_fork_transition_excess_blob_gas_at_blob_genesis(
     )
 
 
+@pytest.mark.valid_for_bpo_forks
 @pytest.mark.valid_at_transition_to("Prague", subsequent_forks=True)
 @pytest.mark.parametrize_by_fork(
     "post_fork_block_count,pre_fork_blobs_per_block,post_fork_blobs_per_block",

tests/osaka/eip7823_modexp_upper_bounds/test_modexp_upper_bounds.py

@@ -283,7 +283,7 @@ def test_modexp_upper_bounds(
         ),
     ],
 )
-@pytest.mark.valid_at_transition_to("Osaka", subsequent_forks=True)
+@pytest.mark.valid_at_transition_to("Osaka")
 def test_modexp_upper_bounds_fork_transition(
     blockchain_test: BlockchainTestFiller,
     pre: Alloc,

tests/osaka/eip7825_transaction_gas_limit_cap/test_tx_gas_limit_transition_fork.py

@@ -28,7 +28,7 @@
 @EIPChecklist.ModifiedTransactionValidityConstraint.Test.ForkTransition.RejectedBeforeFork()
 @EIPChecklist.ModifiedTransactionValidityConstraint.Test.ForkTransition.AcceptedAfterFork()
 @EIPChecklist.ModifiedTransactionValidityConstraint.Test.ForkTransition.RejectedAfterFork()
-@pytest.mark.valid_at_transition_to("Osaka", subsequent_forks=True)
+@pytest.mark.valid_at_transition_to("Osaka")
 @pytest.mark.parametrize(
     "transaction_at_cap",
     [

tests/osaka/eip7883_modexp_gas_increase/test_modexp_thresholds_transition.py

@@ -21,7 +21,7 @@
 REFERENCE_SPEC_GIT_PATH = ref_spec_7883.git_path
 REFERENCE_SPEC_VERSION = ref_spec_7883.version
 
-pytestmark = pytest.mark.valid_at_transition_to("Osaka", subsequent_forks=True)
+pytestmark = pytest.mark.valid_at_transition_to("Osaka")
 
 
 @pytest.mark.parametrize(

tests/osaka/eip7939_count_leading_zeros/test_count_leading_zeros.py

@@ -284,7 +284,7 @@ def test_clz_push_operation_same_value(
 
 @EIPChecklist.Opcode.Test.ForkTransition.Invalid()
 @EIPChecklist.Opcode.Test.ForkTransition.At()
-@pytest.mark.valid_at_transition_to("Osaka", subsequent_forks=True)
+@pytest.mark.valid_at_transition_to("Osaka")
 def test_clz_fork_transition(
     blockchain_test: BlockchainTestFiller, pre: Alloc
 ) -> None: