feat: add fork transition test

Author: LouisTsai-Csie

tests/osaka/eip7883_modexp_gas_increase/test_modexp_thresholds_transition.py

@@ -0,0 +1,86 @@
+"""Test ModExp gas cost transition from EIP-7883 before and after the Osaka hard fork."""
+
+import pytest
+
+from ethereum_test_forks import Fork
+from ethereum_test_tools import Account, Alloc, Block, BlockchainTestFiller, Transaction
+from ethereum_test_tools.vm.opcode import Opcodes as Op
+
+from .spec import Spec, ref_spec_7883
+
+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)
+
+
+@pytest.mark.parametrize(
+    "modexp_input,modexp_expected,gas_old,gas_new",
+    [
+        pytest.param(Spec.modexp_input, Spec.modexp_expected, 200, 500),  # Should be 1200
+    ],
+)
+def test_modexp_fork_transition(
+    blockchain_test: BlockchainTestFiller,
+    pre: Alloc,
+    fork: Fork,
+    gas_old: int,
+    gas_new: int,
+    tx_gas_limit: int,
+):
+    """Test ModExp gas cost transition from EIP-7883 before and after the Osaka hard fork."""
+    call_code = Op.CALL(
+        address=Spec.MODEXP_ADDRESS,
+        args_size=Op.CALLDATASIZE,
+    )
+
+    gas_costs = fork.gas_costs()
+    extra_gas = (
+        gas_costs.G_WARM_ACCOUNT_ACCESS
+        + (gas_costs.G_VERY_LOW * (len(Op.CALL.kwargs) - 2))  # type: ignore
+        + (gas_costs.G_BASE * 3)
+    )
+    code = (
+        Op.CALLDATACOPY(dest_offset=0, offset=0, size=Op.CALLDATASIZE)
+        + Op.GAS  # [gas_start]
+        + call_code  # [gas_start, call_result]
+        + Op.GAS  # [gas_start, call_result, gas_end]
+        + Op.SWAP1  # [gas_start, gas_end, call_result]
+        + Op.POP  # [gas_start, gas_end]
+        + Op.PUSH2[extra_gas]  # [gas_start, gas_end, extra_gas]
+        + Op.ADD  # [gas_start, gas_end + extra_gas]
+        + Op.SWAP1  # [gas_end + extra_gas, gas_start]
+        + Op.SUB  # [gas_start - (gas_end + extra_gas)]
+        + Op.TIMESTAMP  # [gas_start - (gas_end + extra_gas), TIMESTAMP]
+        + Op.SSTORE  # []
+    )
+
+    senders = [pre.fund_eoa() for _ in range(3)]
+    contracts = [pre.deploy_contract(code) for _ in range(3)]
+    timestamps = [14_999, 15_000, 15_001]
+    gas_values = [gas_old, gas_new, gas_new]
+
+    blocks = [
+        Block(
+            timestamp=ts,
+            txs=[
+                Transaction(
+                    to=contract,
+                    sender=sender,
+                    gas_limit=tx_gas_limit,
+                )
+            ],
+        )
+        for ts, contract, sender in zip(timestamps, contracts, senders, strict=False)
+    ]
+
+    post = {
+        contract: Account(storage={ts: gas})
+        for contract, ts, gas in zip(contracts, timestamps, gas_values, strict=False)
+    }
+
+    blockchain_test(
+        pre=pre,
+        blocks=blocks,
+        post=post,
+    )