The Art of Software Testing, Second Edition

9.1. Basic E-commerce Architecture

Before diving into testing Internet-based applications, we will provide an overview of the three-tier client-server (C/S) architecture used in a typical Internet-based e-commerce application. Conceptually, each tier is treated as a black box with well-defined interfaces. This model allows you to change the internals of each tier without worrying about breaking another tier. Figure 9.1 illustrates each tier and the associated components used by most e-commerce sites.

Although not an official tier in the architecture, the client side and its relevance are worth discussing. Most of the access to your applications occurs from a Web browser running on a computer, although many devices, such as cell phones, refrigerators, pagers, and automobiles, are being developed that can connect to the Internet. Browsers vary dramatically in how they render content from a Website. As we discuss later in this chapter, testing for browser compatibility is one challenge associated with testing Internet applications. Vendors loosely follow published standards to help make browsers behave consistently, but they also build in proprietary enhancements that cause inconsistent behavior. The remainder of the clients employ custom applications that use the Internet as a pipeline to a particular site. In this scenario, the application mimics a standard client-server application you might find on a company's local area network.

Figure 9.1. Typical architecture of an e-commerce ...