The Tester Abstraction Layer (TAL) is a novel approach to ATE test design that provides a platform-agnostic and extensible Application Programming Interface (API) in order to simplify test development. TAL is designed to abstract away the complexities and idiosyncrasies of individual testing platforms and provide a unified, easy-to-use API for test development. This abstraction layer allows test program developers to write tests once and run them on multiple platforms without any modifications. TAL acts as a bridge between test program logic and the underlying testing platforms, encapsulating differences between the platforms and translating generic test commands into platform-specific instructions. TAL additionally allows for test portability. Since TAL provides a platform-agnostic API, tests written for one platform can be easily ported to another platform. This can be particularly useful with multi-tiered test strategies, where common test logic needs to be executed on multiple platforms, such as ATE and SLT, to ensure test completeness. This document will describe the design principles, benefits, and applications of TAL, namely siting the Tester API project.