In recent years, embedded systems have become so complex and the development time to market is required to be shorter than before. As embedded systems include more functions for new services, embedded software gradually grow in size, and development costs and time are increasing. In order to overcome this serious matter, we need a customized design and test technique for embedded software. In this paper, we present a software architecture style for embedded software. It facilitates the composition of reusable functions and helps developers to reduce development time. Because the costs associated with revealing errors of embedded software in applications are rising, we propose a test method and tools for target environments.