test_sstore_dirty_slot_refund()

Documentation for tests/amsterdam/eip8037_state_creation_gas_cost_increase/test_state_gas_sstore.py::test_sstore_dirty_slot_refund@622620d8.

Generate fixtures for these test cases for Amsterdam with:

fill -v tests/amsterdam/eip8037_state_creation_gas_cost_increase/test_state_gas_sstore.py::test_sstore_dirty_slot_refund --fork Amsterdam

Test the refund for a second write to a slot already changed in the same transaction.

The write cost was paid by the first change, so the second write is charged the warm access alone. Clearing a dirty slot still earns the storage-clear refund; clearing and then writing the original value back reverses that refund and returns the write cost instead.

Source code in tests/amsterdam/eip8037_state_creation_gas_cost_increase/test_state_gas_sstore.py

@pytest.mark.parametrize(
    "initial_value,post_value",
    [
        pytest.param(2, 0, id="dirty_clear"),
        pytest.param(0, 1, id="clear_then_restore_original"),
    ],
)
@pytest.mark.valid_from("EIP8037")
def test_sstore_dirty_slot_refund(
    state_test: StateTestFiller,
    pre: Alloc,
    fork: Fork,
    initial_value: int,
    post_value: int,
) -> None:
    """
    Test the refund for a second write to a slot already changed in the
    same transaction.

    The write cost was paid by the first change, so the second write is
    charged the warm access alone. Clearing a dirty slot still earns the
    storage-clear refund; clearing and then writing the original value
    back reverses that refund and returns the write cost instead.
    """
    original = 1
    code = Op.SSTORE(
        0,
        initial_value,
        # gas accounting
        original_value=original,
        current_value=original,
        new_value=initial_value,
    ) + Op.SSTORE(
        0,
        post_value,
        # gas accounting
        key_warm=True,
        original_value=original,
        current_value=initial_value,
        new_value=post_value,
    )
    assert code.state_cost(fork) == 0, "a nonzero slot grows no state"
    assert code.state_refund(fork) == 0, "no state charge, no state refund"
    assert code.refund(fork) > 0, "the dirty second write earns a refund"

    pre_refund_gas = (
        fork.transaction_intrinsic_cost_calculator()()
        + code.execution_cost(fork)
    )

    contract = pre.deploy_contract(code=code, storage={0: original})

    tx = Transaction(
        to=contract,
        state_gas_reservoir=0,
        sender=pre.fund_eoa(),
        expected_receipt=TransactionReceipt(
            cumulative_gas_used=sender_gas_used(fork, pre_refund_gas, code)
        ),
    )

    state_test(
        pre=pre,
        post={contract: Account(storage={0: post_value})},
        tx=tx,
        blockchain_test_header_verify=Header(gas_used=pre_refund_gas),
    )

Parametrized Test Cases

This test generates 2 parametrized test cases across 1 fork.