Reviewing Form Submission

As in the case of creating users (signup), the first step in creating sessions (signin) is to handle invalid input. We already have tests for the signup failure (Listing 8.5), and the application code is simple apart from a couple of subtleties. We’ll start by reviewing what happens when a form gets submitted, and then arrange for helpful error messages to appear in the case of signin failure (as mocked up in Figure 8.2.) Then we’ll lay the foundation for successful signin (Section 8.2) by evaluating each signin submission based on the validity of its email/password combination

  Let’s start by defining a minimalist create action for the Sessions controller (Listing 8.9), which does nothing but render the new view. Submitting the/sessions/new form with blank fields then yields the result shown in Figure 8.5.

                          Figure 8.5 The initial failed signin, with create as in Listing 8.9.