The application we have built so far allows users to choose a username to identify themselves. However, they only retain this identity for the duration of their browser session. It's important to allow users to retain a consistent identity from one session to the next. This allows us to build richer user experiences. Some websites (such as Facebook) couldn't offer their main functionality at all without being able to identify users.
Identifying users requires us to implement authentication. In this chapter, we will cover the following topics:
Implementing third-party authentication via social networking sites
Associating third-party identities with our own user data
Simulating user authentication to support integration testing