In recent years, the constraints of monolithic silicon have pushed device design to its limits, necessitating innovative approaches to meet future PPA (Power, Performance, Area) targets. The solution lies in disaggregated designs utilizing chiplets interconnected via high-bandwidth interfaces. These chiplets, such as MPUs, GPUs, or AI accelerators, are arranged in 2.5D or 3DIC configurations within a single package, leveraging standards like JEDEC, HBM and UCIe for efficient logic-to-memory and logic-to-logic connections. However, the transition to these high-bandwidth die-to-die interfaces introduces new challenges, particularly in ensuring robust testability during production. This becomes crucial as Silent Data Corruption (SDC) emerges as a critical defect class in large-scale CPU deployments for high-bandwidth ML/AI applications, necessitating significant increases in vector loads for comprehensive functional testing and workload emulation. Addressing these demands requires a deep dive into bandwidth requirements for data flows across various mobile and HPC devices. This shift also poses a formidable challenge to wafer and package testing technologies, prompting exploration into effective ATE strategies for chiplet-based architectures. These strategies must accommodate Signal Integrity (SI) and Power Integrity (PI) considerations, alongside thermal management, and protection protocols for sensitive components. The stringent standards governing these interfaces prioritize high density and low power consumption, limiting external test access during wafer tests using ATE due to micro bumps and dense pitch configurations. Consequently, exploring viable test access methods becomes pivotal, weighing area, performance, cost, and non-recurring engineering (NRE) implications at each stage of integration. Current methodologies span a spectrum from Kbps to Gbps using NRZ protocols, necessitating precise determination of aggregate bandwidth to initialize DUTs and to execute extensive test pattern sets and workloads. While customized solutions presently address die access during wafer tests, industry momentum leans towards standardized solutions for high-bandwidth ATE access to UCIe-enabled chiplets, both on-wafer and in-package. This paper navigates these complexities, offering insights into the challenges posed, diverse approaches available, and a quantitative comparison of each test access method. By delving into these intricacies, we aim to pave the way for optimized testing solutions that align with the evolving landscape of advanced semiconductor technologies.