Motivation and Strategy

The basic idea behind the feed is simple. Figure 11.19 shows a sample microposts database table and the resulting feed. The purpose of a feed is to pull out the microposts whose user ids correspond to the users being followed by the current user (and the current user itself), as indicated by the arrows in the diagram.

         Since we need a way to find all the microposts from users followed by a given user, we’ll plan on implementing a method called from_users_followed_by, which we will use as follows:

Although we don’t yet know how to implement it, we can already write tests for for its functionality. The key is to check all three requirements for the feed: microposts for followed users and the user itself should be included in the feed, but a post from an  

unfollowed user should not be included. Two of these requirements already appear in our tests: Listing 10.38 verifies that a user’s own microposts appear in the feed, while the micropost from an unfollowed user doesn’t appear. Now that we know how to follow users, we can add a third type of test, this time checking that the microposts of a followed user appear in the feed, as shown in Listing 11.41.