# Ethereum Upgrade Tests Can Miss Live-App Failures, Sprinter CEO Says

By Simon Yoon

Canonical URL: https://www.tokenpost.com/news/technology/55194
Published: 2026-11-12T09:46:43.000Z
Updated: 2026-11-12T09:46:43.000Z
Section: Technology

> Greg Markou said a MetaMask-related assumption went undetected during the August 2021 EIP-1559 upgrade, affecting nearly every application that relied on web3.js.

Ethereum testnets may not catch every combination of software that affects live applications during a network upgrade, Sprinter co-founder and CEO Greg Markou said, pointing to a 2021 incident involving web3.js.

Markou maintained web3.js, a JavaScript library that lets applications communicate with Ethereum, during the EIP-1559 upgrade, which was part of the London hard fork in August 2021. He said an assumption involving MetaMask went undetected in an update tied to the upgrade and affected nearly every application that relied on the library.

Testnets let developers try changes before they reach Ethereum’s main network. Markou said they may not reproduce every combination of wallets, libraries and smart contracts that applications encounter on the live network, leaving some edge cases undetected during testing.

Markou called Ethereum an “absolute monolithic beast” while discussing how difficult it can be to predict the effects of a change across connected software.