Arbitrum fork can't fork Arbitrum block number on tests

[hanzel98]

Component

Forge

Have you ensured that all of these are up to date?

• [X] Foundry
• [X] Foundryup

What version of Foundry are you on?

forge 0.2.0 (b174c3a 2024-02-09T00:19:10.198273000Z)

What command(s) is the bug in?

forge test

Operating System

macOS (Apple Silicon)

Describe the bug

I'm trying to use an Arbitrum fork in my tests, but I can't set the block number.

For some reason instead of using the arbitrum block number that I'm passing it, it is using a different block number. It recognizes the chainId change to Arbitrum but not the block number.

I'm simply running forge test -vv because the instructions for the fork are indicated inside the setup() function

I'm thinking this might be an issue with foundry

Sample code to reproduce the error

// SPDX-License-Identifier: MIT

pragma solidity 0.8.21;

import "forge-std/Test.sol";

contract SomeTest is Test {
    function setUp() external {
        console.log("1block.chainid:", block.chainid);
        console.log("1block.number:", block.number);
        console.log("1block.timestamp:", block.timestamp);
        vm.createSelectFork(vm.envString("RPC_ARB_MAINNET"), 179_639_839);
        console.log("2block.chainid:", block.chainid); // This must be 179_639_839 but it isn't
        console.log("2block.number:", block.number);
        console.log("2block.timestamp:", block.timestamp);
    }

    function test_ArbitrumBlockNumber() public {
        console.log("Something");
    }
}

[grandizzy]

that's by intent the L1 block see https://github.com/foundry-rs/foundry/blob/master/crates/evm/core/src/utils.rs#L70C1-L75C41

                // on arbitrum `block.number` is the L1 block which is included in the
                // `l1BlockNumber` field

[hanzel98]

that's by intent the L1 block see https://github.com/foundry-rs/foundry/blob/master/crates/evm/core/src/utils.rs#L70C1-L75C41

                // on arbitrum `block.number` is the L1 block which is included in the
                // `l1BlockNumber` field

If that is intentional how can I run tests on an arbitrum fork (with a specific arbitrum block) because it overrides the value with the mainnet block?

Or how can I disable that behavior, I don't need the Ethereum block, I need the arbitrum block.

Also is there any explanation of why this override of the block number is needed? Why if I'm testing arbitrum it changes to Ethereum blocks?

[grandizzy]

that's by intent the L1 block see https://github.com/foundry-rs/foundry/blob/master/crates/evm/core/src/utils.rs#L70C1-L75C41

                // on arbitrum `block.number` is the L1 block which is included in the
                // `l1BlockNumber` field

If that is intentional how can I run tests on an arbitrum fork (with a specific arbitrum block) because it overrides the value with the mainnet block?

Or how can I disable that behavior, I don't need the Ethereum block, I need the arbitrum block.

Also is there any explanation of why this override of the block number is needed? Why if I'm testing arbitrum it changes to Ethereum blocks?

I think you would need to test your contracts with correct chain behaviour https://docs.arbitrum.io/for-devs/concepts/differences-between-arbitrum-ethereum/block-numbers-and-time#ethereum-block-numbers-within-arbitrum

[zerosnacks]

Marking as duplicate of https://github.com/foundry-rs/foundry/issues/5085