In the frenzied build-up to Ethereum’s much-anticipated merge, the network’s developers have deployed test after test to make sure everything goes smoothly when the second-largest cryptocurrency by market capitalization transitions to proof of stake sometime next week

Ethereum today successfully completed what its developers say is the absolute final dress rehearsal for the historic and massive upgrade, which is likely to occur between September 13 and 15. 

The Ethereum mainnet’s 13th shadow fork went live earlier today, apparently without a hitch. Shadow forks are focused trial runs of aspects of the merge, which test for potential issues and simulate the act of shifting the Ethereum mainnet’s underlying mechanism from the current, proof-of-work mining model to proof of stake, which will end the practice of mining on the network. 

In speaking with Decrypt, a number of Ethereum developers confirmed that the network's final shadow fork today was successfully deployed. “No issues surfaced,” Ethereum core developer Marius Van Der Wijden told. Decrypt.

Last week, during Bellatrix, a key pre-merge upgrade, the Ethereum network encountered some hiccups when its “missed block rate” spiked by some 1,700%. 

The missed-block-rate metric measures how frequently the Ethereum network fails to verify a block of transactions slated for validation. Typically, about 0.5% of blocks encounter this issue; in the hours following the Bellatrix upgrade, that figure surged to 9%. 

Ethereum’s developers chalked up the snag to a lack of preparedness from a number of node operators who had yet to update their clients to the proper merge-ready software. Node operators are the individuals and organizations that keep the backend infrastructure of the Ethereum network operating. 

At the time of the Bellatrix upgrade, 25.2% of Ethereum’s nodes still had yet to upgrade their software. As of writing, that figure has lowered to 15.4%, per Ethernodes

Terence Tsao, an Ethereum core developer, told Decrypt that today’s shadow fork tested this missed block rate issue, and found it to be functioning “basically perfectly.”

The network’s developers have been running dress rehearsals of the merge almost weekly for the last few months, attempting to game out any scenarios that could potentially derail or delay its execution. With tens of billions of dollars worth of digital assets, apps, and decentralized finance instruments built atop the Ethereum network, there is essentially no margin for error. 

Ethereum’s developers have continually signaled assuredness that the merge will go exactly as planned. Nonetheless, the test runs have continued—perhaps, more than anything else, to offer developers some peace of mind. 

“It’s just sanity checking at this point,” said Van Der Wijden.

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