pub(super) fn mock_l2_client_hanging() -> MockClient<L2> {
    MockClient::builder(L2::default())
        .method("eth_chainId", || Ok(U64::from(270)))
        .method("zks_L1ChainId", || Ok(U64::from(9)))
        .method("zks_L1BatchNumber", || {
            Err::<(), _>(ClientError::RequestTimeout)
        })
        .method("eth_blockNumber", || {
            Err::<(), _>(ClientError::RequestTimeout)
        })
        .method("zks_getFeeParams", || Ok(FeeParams::sensible_v1_default()))
        .method("en_whitelistedTokensForAA", || Ok([] as [Address; 0]))
        .build()
}
Creates a mock L2 client that will mimic request timeouts on block info requests.
core/bin/external_node/src/tests/utils.rs