test_exchange_stack_underflow()¶

@EIPChecklist.Opcode.Test.StackUnderflow()
@pytest.mark.parametrize(
    "immediate",
    # Boundaries of both valid ranges (0x00, 0x51, 0x80, 0xFF)
    [0, 78, 79, 80, 81, 128, 129, 255],
    ids=lambda x: f"underflow_imm_{x}",
)
def test_exchange_stack_underflow(
    immediate: int,
    pre: Alloc,
    state_test: StateTestFiller,
) -> None:
    """Test EXCHANGE causes transaction failure on stack underflow."""
    sender = pre.fund_eoa()

    # EXCHANGE needs m+1 items. Push one less to trigger underflow.
    n, m = decode_pair(immediate)
    insufficient_depth = m  # m+1 required, push only m

    code = Bytecode()
    code += Op.SSTORE(0, 1)  # Marker

    for i in range(insufficient_depth):
        code += Op.PUSH1(i)

    code += Op.EXCHANGE[immediate.to_bytes(1, "big")]
    code += Op.SSTORE(0, 2)  # Should never execute
    code += Op.STOP

    contract_address = pre.deploy_contract(code=code)
    tx = Transaction(to=contract_address, sender=sender)

    # Transaction should fail, contract storage unchanged
    post = {contract_address: Account(storage={})}

    state_test(pre=pre, post=post, tx=tx)