feat(tests): add empty precompile top-frame charge test

tests/amsterdam/eip2780_reduce_intrinsic_tx_gas/test_top_frame_charges.py

@@ -19,6 +19,7 @@
 import pytest
 from execution_testing import (
     Account,
+    Address,
     Alloc,
     Fork,
     Op,
@@ -104,6 +105,60 @@ def test_top_frame_state_charge(
     state_test(pre=pre, tx=tx, post=post)
 
 
+def test_top_frame_state_charge_empty_precompile(
+    fork: Fork,
+    pre: Alloc,
+    state_test: StateTestFiller,
+) -> None:
+    """
+    An empty precompile recipient is still empty per EIP-161, so a
+    value-moving transaction to it must pay the top-frame
+    ``NEW_ACCOUNT`` state-gas charge.
+
+    The gas limit is one short of covering that state charge. Without
+    the charge, the transaction would reach the identity precompile and
+    transfer value, which makes this a direct regression test for a
+    precompile carve-out.
+    """
+    sender_initial_balance = 10**18
+    sender = pre.fund_eoa(sender_initial_balance)
+    identity_precompile = Address(0x04)
+
+    value = 1
+    intrinsic_gas = fork.transaction_intrinsic_cost_calculator()(
+        sends_value=True,
+        recipient_type=RecipientType.PRECOMPILE,
+        return_cost_deducted_prior_execution=True,
+    )
+    top_frame_state_gas = fork.transaction_top_frame_state_gas(
+        sends_value=True,
+        recipient_type=RecipientType.EMPTY_ACCOUNT,
+    )
+    assert top_frame_state_gas > 0, (
+        "top-frame state gas must be non-zero for empty recipients"
+    )
+
+    gas_price = 1_000_000_000
+    gas_limit = intrinsic_gas + top_frame_state_gas - 1
+    tx = Transaction(
+        sender=sender,
+        to=identity_precompile,
+        value=value,
+        gas_limit=gas_limit,
+        gas_price=gas_price,
+    )
+
+    post = {
+        sender: Account(
+            nonce=1,
+            balance=sender_initial_balance - gas_limit * gas_price,
+        ),
+        identity_precompile: None,
+    }
+
+    state_test(pre=pre, tx=tx, post=post)
+
+
 @pytest.mark.parametrize("outcome", ["oog", "success", "evm_reverts"])
 @pytest.mark.parametrize(
     "value",

tests/amsterdam/eip2780_reduce_intrinsic_tx_gas/test_value_moving_transactions.py

@@ -339,34 +339,46 @@ def test_value_move_to_precompiles(
         recipient_type=state_recipient_type,
     )
 
-    # Precompile execution gas varies per precompile and input; pick a
-    # buffer large enough to cover the most expensive precompile in the
-    # matrix on top of the intrinsic and the (spilled) state charge.
-    precompile_execution_budget = 100_000
-    tx_gas_limit = (
-        intrinsic_gas + top_frame_state_gas + precompile_execution_budget
-    )
     gas_price = 1_000_000_000
 
     tx = Transaction(
         sender=sender,
         to=precompile,
         value=value,
         data=tx_data,
-        gas_limit=tx_gas_limit,
         gas_price=gas_price,
     )
 
-    # Exact sender balance is not checked because precompile execution
-    # gas varies; verify value receipt and sender nonce instead.
+    # Exact sender balance is generally not checked because precompile
+    # execution gas varies across the matrix. For identity with empty
+    # calldata, the execution gas is deterministic, so pin the exact
+    # balance to make the empty-precompile ``NEW_ACCOUNT`` charge a
+    # source-level assertion.
     final_precompile_balance = pre_funded_amount + value
     expected_precompile: Account | None
     if final_precompile_balance > 0:
         expected_precompile = Account(balance=final_precompile_balance)
     else:
         expected_precompile = None
+    expected_sender = Account(nonce=1)
+    if precompile == Address(0x04):
+        gas_costs = fork.gas_costs()
+        precompile_execution_gas = (
+            gas_costs.PRECOMPILE_IDENTITY_BASE
+            + gas_costs.PRECOMPILE_IDENTITY_PER_WORD
+            * ((len(tx_data) + 31) // 32)
+        )
+        total_gas_cost = (
+            intrinsic_gas + top_frame_state_gas + precompile_execution_gas
+        )
+        expected_sender = Account(
+            nonce=1,
+            balance=(
+                sender_initial_balance - value - total_gas_cost * gas_price
+            ),
+        )
     post = {
-        sender: Account(nonce=1),
+        sender: expected_sender,
         precompile: expected_precompile,
     }