Declare GET "/" route

In order to access the GET / route in UserSharesAMessageTest, declare a route using the get route helper, which delegates its arguments to the underlying match route helper, in order to handle requests made with the GET HTTP Verb.

The get declaration accepts options. The controller: option instructs the router to route requests with the GET verb and the "/" path to the controller name with the corresponding name.

In this commit’s case, controller: "notes" corresponds to the NotesController.

Another option the get helper accepts is action:. The value assigned to the action: key instructs the router to route requests that match the criteria to the corresponding controller’s instance method.

In this commit’s case, action: "index" corresponds to the NotesController#index instance method.

Once the route exists, the request made in the test yields a new error:

Error:
UserSharesAMessagesTest#test_visiting_the_index:
ActionController::RoutingError: uninitialized constant NotesController
Did you mean?  ActionController