Worked on enhancing the stability and usability of ZTEST shell integration within the zephyrproject-rtos/zephyr repository, focusing on improving test workflow reliability for POSIX targets. Addressed a key bug by adding missing ztest_posix functions to support compilation when ZTEST_SHELL is enabled, and modified test control flow to prevent shell termination after test execution, preserving session continuity. Disabled the redundant -test command-line option in favor of shell-based filtering, streamlining test selection and interaction. Utilized C programming and embedded systems expertise, along with testing frameworks and unit testing, to deliver more robust and predictable test runs for developers using Zephyr.