Create comments for an article

Add a CommentsControler (with only a create action as-of now) and the
associated test class. Modify the articles show view to provide a list
of comments for the article and a form for adding a new comment to the
article. Modify the ArticlesControllerTest with assertions about the
new functionality for the show action and view.

Completes Rails Getting Started Guide:
* 8 Adding a Second Model
  * 8.4 Generating a Controller

app/controllers/comments_controller.rb

@@ -0,0 +1,12 @@
+class CommentsController < ApplicationController
+  def create
+    @article = Article.find(params[:article_id])
+    @comment = @article.comments.create(comment_params)
+    redirect_to article_path(@article), notice: "Comment was successfully created."
+  end
+
+  private
+  def comment_params
+    params.require(:comment).permit(:commenter, :body)
+  end
+end

app/helpers/comments_helper.rb

@@ -0,0 +1,2 @@
+module CommentsHelper
+end

app/views/articles/show.html.erb

@@ -9,3 +9,32 @@
   <li><%= link_to "Destroy", article_path(@article),
         data: { turbo_method: :delete, turbo_confirm: "Are you sure?" } %></li>
 </ul>
+
+
+<h2>Comments</h2>
+<% @article.comments.each do |comment| %>
+  <p class="commenter">
+    <strong>Commenter:</strong>
+    <%= comment.commenter %>
+  </p>
+
+  <p class="comment-body">
+    <strong>Comment:</strong>
+    <%= comment.body %>
+  </p>
+<% end %>
+
+<h2>Add a comment:</h2>
+<%= form_with model: [ @article, @article.comments.build ] do |form| %>
+  <p>
+    <%= form.label :commenter %><br>
+    <%= form.text_field :commenter %>
+  </p>
+  <p>
+    <%= form.label :body %><br>
+    <%= form.text_area :body %>
+  </p>
+  <p>
+    <%= form.submit %>
+  </p>
+<% end %>

test/controllers/articles_controller_test.rb

@@ -13,18 +13,24 @@ def setup
   test "should get index" do
     get articles_url
     assert_response :success
-    assert_select 'h1', 'Articles'
-    assert_select 'li', Article.count
-    assert_select 'a', 'New Article'
+    assert_select "h1", "Articles"
+    assert_select "li", Article.count
+    assert_select "a", "New Article"
   end
 
   test "should get show" do
     get article_url(@article)
     assert_response :success
-    assert_select 'h1', @article.title
-    assert_select 'p', @article.body
-    assert_select 'a', 'Edit'
-    assert_select 'a', 'Destroy'
+    assert_select "h1", @article.title
+    assert_select "p", @article.body
+    assert_select "a", "Edit"
+    assert_select "a", "Destroy"
+    assert_select "h2", "Comments"
+    assert_select "p.commenter", @article.comments.count
+    assert_select "p.comment-body", @article.comments.count
+    assert_select "h2", "Add a comment:"
+    assert_select "form"
+    assert_select "form p", 3
   end
 
   test "should get new" do

test/controllers/comments_controller_test.rb

@@ -0,0 +1,27 @@
+require "test_helper"
+
+class CommentsControllerTest < ActionDispatch::IntegrationTest
+  def setup
+    @article = articles(:nerd)
+  end
+
+  test "should create comment" do
+    commenter = "A new commenter"
+    body = "This is my comment on the Nerd Dice article."
+    assert_difference("Comment.count") do
+      post article_comments_url(@article), params: {
+        article_id: @article.id,
+        comment: {
+          commenter: commenter,
+          body: body
+        }
+      }
+    end
+
+    comment = @article.comments.last
+    assert_redirected_to article_path(@article)
+    assert_equal commenter, comment.commenter
+    assert_equal body, comment.body
+    assert_equal "Comment was successfully created.", flash[:notice]
+  end
+end