Justyna Michalak enhanced the robustness of firmware upgrade testing in the nrfconnect/sdk-nrf repository by expanding test coverage for monotonic counter upgrades and bootloader failure handling. She removed the xfail quarantine marker from a key test, enabling active verification of monotonic counter upgrade limits, and updated bootloader tests to validate fallback behavior when upgrades fail. Using Python and her expertise in bootloader development and testing, Justyna ensured that the bootloader correctly reports new image versions while safely reverting to previous firmware slots. Her work reduced production risk and improved regression feedback, demonstrating a thorough approach to validating upgrade path resilience.