Fixes issue brought up in elixirschool#1043 (elixirschool#1086)

* Fixes issue brought up in elixirschool#1043

* Fixes error described in elixirschool#1043 (comment)
* Updates lesson for Elixir 1.4 (1.3 not supported)
* Clearer code formatting
* Improved program output
* Adds instructions to RouterTest

* Plug Version 1.1.1

lessons/specifics/plug.md

@@ -1,5 +1,5 @@
 ---
-version: 1.1.0
+version: 1.1.1
 layout: page
 title: Plug
 category: specifics
@@ -18,7 +18,7 @@ After that, we'll learn about Plug's router and how to add a Plug to an existing
 
 ## Prerequisites
 
-This tutorial assumes you have Elixir and `mix` installed already.
+This tutorial assumes you have Elixir 1.4 or higher, and `mix` installed already.
 
 If you don't have a project started, create one like this:
 
@@ -35,8 +35,10 @@ The first thing to do is add both Plug and a web server (we'll be using Cowboy)
 
 ```elixir
 defp deps do
- [{:cowboy, "~> 1.1.2"},
- {:plug, "~> 1.3.4"}]
+ [
+ {:cowboy, "~> 1.1.2"},
+ {:plug, "~> 1.3.4"},
+ ]
 end
 ```
 
@@ -62,7 +64,7 @@ defmodule Example.HelloWorldPlug do
  def call(conn, _opts) do
  conn
  |> put_resp_content_type("text/plain")
- |> send_resp(200, "Hello World!")
+ |> send_resp(200, "Hello World!\n")
  end
 end
 ```
@@ -103,15 +105,14 @@ This supervises Cowboy, and in turn, supervises our `HelloWorldPlug`.
 In the `Plug.Adapters.Cowboy.child_spec/4` call, the third argument will be passed to `Example.HelloWorldPlug.init/1`.
 
 We're not finished yet. Open `mix.exs` again, and find the `applications` function.
-For now, it'll provide two things:
-1) A list of dependency applications (`cowboy`, `logger`, and `plug`) that need to start up, and
-2) Configuration for our own application, which should also start up automatically.
+We need to add configuration for our own application, which should also cause it to start up automatically.
+
 Let's update it to do that:
 
 ```elixir
 def application do
  [
- applications: [:cowboy, :logger, :plug],
+ extra_applications: [:logger],
  mod: {Example, []}
  ]
 end
@@ -159,11 +160,11 @@ Swap out the `Example.HelloWorldPlug` plug with the new router:
 
 ```elixir
 def start(_type, _args) do
-  children = [
-  Plug.Adapters.Cowboy.child_spec(:http, Example.Router, [], port: 8080)
-  ]
-  Logger.info "Started application"
-  Supervisor.start_link(children, strategy: :one_for_one)
+ children = [
+ Plug.Adapters.Cowboy.child_spec(:http, Example.Router, [], port: 8080)
+ ]
+ Logger.info "Started application"
+ Supervisor.start_link(children, strategy: :one_for_one)
 end
 ```
 
@@ -247,9 +248,9 @@ defmodule Example.Router do
  plug :match
  plug :dispatch
 
- get "/", do: send_resp(conn, 200, "Welcome")
- post "/upload", do: send_resp(conn, 201, "Uploaded")
- match _, do: send_resp(conn, 404, "Oops!")
+ get "/", do: send_resp(conn, 200, "Welcome\n")
+ post "/upload", do: send_resp(conn, 201, "Uploaded\n")
+ match _, do: send_resp(conn, 404, "Oops!\n")
 end
 ```
 
@@ -263,9 +264,11 @@ With those changes in place our code should look something like this:
 
 ```elixir
 def application do
- [applications: [:cowboy, :logger, :plug],
- mod: {Example, []},
- env: [cowboy_port: 8080]]
+ [
+ extra_applications: [:logger],
+ mod: {Example, []},
+ env: [cowboy_port: 8080]
+ ]
 end
 ```
 
@@ -282,7 +285,7 @@ defmodule Example do
  port = Application.get_env(:example, :cowboy_port, 8080)
 
  children = [
- Plug.Adapters.Cowboy.child_spec(:http, Example.Plug.Router, [], port: port)
+ Plug.Adapters.Cowboy.child_spec(:http, Example.Router, [], port: port)
  ]
 
  Supervisor.start_link(children, strategy: :one_for_one)
@@ -311,7 +314,7 @@ $ mix run --no-halt
 Testing Plugs is pretty straightforward thanks to `Plug.Test`.
 It includes a number of convenience functions to make testing easy.
 
-See if you can follow along with the router test:
+Write the following test to `test/example/router_test.exs`:
 
 ```elixir
 defmodule Example.RouterTest do
@@ -352,6 +355,12 @@ defmodule Example.RouterTest do
 end
 ```
 
+Run it with this:
+
+```shell
+mix test test/example/router_test.exs
+```
+
 ## Available Plugs
 
 There are a number of Plugs available out-of-the-box.