As the proposed date for the Ethereum Shanghai update draws closer, developers have created a testing environment called a “shadow fork,” according to a January 23 tweet thread by Go-Ethereum developer Marius Van Der Wijden. The new testnet appears to have been created in order to test the conditions needed for Ether (ETH) staking withdrawals, which are currently disabled but are intended to become enabled in the update.

Withdrawal-Mainnet-Shadow-Fork-1 is finalizing

It started out with a few issues because the config wasn’t correctly applied on geth (we disallow overriding the mainnet config). The config is applied correctly and all nodes are in agreement. We will start some evil nodes,.

— MariusVanDerWijden (@vdWijden) January 23, 2023

The name of the testnet is “Withdrawal-Mainnet-Shadow-Fork-1.” According to Web3 node provider Alchemy, a “shadow fork” is a fork of the mainnet that is intended to be used only for testing purposes.

Van Der Wijden stated that he and another developer named “Potuz” will create malicious nodes that will send bad blocks and messages to other nodes on the testnet and try to convince them to join a false version of the network. For now, the network is running smoothly, but Van Der Wijden has stated that he wants to “see if Potuz and I can break it.” This is apparently being done to see if the upgrade can prevent malicious attacks or if further changes need to be made before it is implemented on mainnet.

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The launch of this testnet comes after devs have expressed an increasing urgency to make Ether staking withdrawals a reality. On Jan. 6, they held a meeting during which they agreed to exclude the proposed EVM Object Format (EOF) from the Shanghai upgrade. EOF was intended to make Ethereum easier to upgrade in the future. But because of its complexity, the devs decided to leave it out of Shanghai for fear that it would delay withdrawal implementation.

Over 14.5 million ETH (over $23 billion worth at the time this is being written) has been deposited into the Ethereum staking contract and cannot currently be withdrawn, according to a December, 2022 report by Nansen. In November, 2022, Ethereum devs came under harsh criticism for allegedly moving the goalpost in regards to enabling withdrawals.

The Shanghai upgrade is currently scheduled to be implemented sometime in March.