test_sstore_refund_quotient_cap()

Documentation for tests/amsterdam/eip8038_state_access_gas_cost_increase/test_sstore_refunds.py::test_sstore_refund_quotient_cap@343274cc.

Generate fixtures for these test cases for Amsterdam with:

fill -v tests/amsterdam/eip8038_state_access_gas_cost_increase/test_sstore_refunds.py::test_sstore_refund_quotient_cap --fork Amsterdam

The applied refund saturates at the EIP-3529 quotient cap.

num_clears distinct non-zero-original slots are each cleared, accruing num_clears * REFUND_STORAGE_CLEAR into refund_counter. A single clear's gross gas is small enough that gas_used // 5 is always below the accrued refund, so the applied refund is the cap and cumulative_gas_used reflects min(gas_used // 5, accrued).

Source code in tests/amsterdam/eip8038_state_access_gas_cost_increase/test_sstore_refunds.py

@EIPChecklist.GasRefundsChanges.Test.RefundCalculation()
@EIPChecklist.GasRefundsChanges.Test.RefundCalculation.Exact()
@pytest.mark.parametrize("num_clears", [1, 8, 32])
def test_sstore_refund_quotient_cap(
    state_test: StateTestFiller,
    pre: Alloc,
    fork: Fork,
    num_clears: int,
) -> None:
    """
    The applied refund saturates at the EIP-3529 quotient cap.

    ``num_clears`` distinct non-zero-original slots are each cleared,
    accruing ``num_clears * REFUND_STORAGE_CLEAR`` into ``refund_counter``.
    A single clear's gross gas is small enough that ``gas_used // 5`` is
    always below the accrued refund, so the applied refund is the cap and
    ``cumulative_gas_used`` reflects ``min(gas_used // 5, accrued)``.
    """
    code = Bytecode()
    for slot in range(num_clears):
        code += Op.SSTORE.with_metadata(
            key_warm=False,
            original_value=1,
            current_value=1,
            new_value=0,
        )(slot, 0)

    contract = pre.deploy_contract(
        code=code,
        storage=dict.fromkeys(range(num_clears), 1),
    )

    # num_clears distinct clears accrue num_clears * REFUND_STORAGE_CLEAR.
    accrued = code.refund(fork)
    intrinsic = fork.transaction_intrinsic_cost_calculator()(
        return_cost_deducted_prior_execution=True
    )
    gross = intrinsic + code.execution_cost(fork)
    # The cap binds for every parametrization (single-clear gross is far
    # below 5x a clear refund).
    cap = gross // 5
    assert cap < accrued
    applied_refund = min(cap, accrued)
    expected_cumulative = gross - applied_refund

    tx = Transaction(
        to=contract,
        sender=pre.fund_eoa(),
        expected_receipt=TransactionReceipt(
            cumulative_gas_used=expected_cumulative
        ),
    )

    post = {contract: Account(storage=dict.fromkeys(range(num_clears), 0))}
    state_test(pre=pre, post=post, tx=tx)

Parametrized Test Cases

This test generates 3 parametrized test cases across 1 fork.