7.1.1 Debug and Rails environments
7.1.2 A Users resource
7.1.4 A Gravatar image and a sidebar
7.2.1 Using form_for
7.3.1 A working form
7.3.2 Strong parameters
7.3.3 Signup error messages
7.3.4 A test for invalid submission
7.4.1 The finished signup form
7.4.2 The flash
7.4.4 A test for valid submission