Add tests for previous and next diary entry navigation

Add tests covering diary entry navigation behaviour,
including cases for first and last entries.

Includes minor updates to navigation markup and
missing locale keys required for tests to pass.

Author: phanq003

app/views/diary_entries/show.html.erb

@@ -17,7 +17,7 @@
 <%= render @diary_entry, :user => @user, :truncated => false %>
 <%= share_buttons(:title => @diary_entry.title, :url => diary_entry_url(@diary_entry.user, @diary_entry)) %>
 
-<nav class="d-flex justify-content-between mb-3">
+<nav class="diary-entry-navigation d-flex justify-content-between mb-3">
   <div>
     <% if @prev_entry %>
       <%= link_to diary_entry_path(@user, @prev_entry), :class => "btn btn-outline-secondary" do %>

config/locales/en.yml

@@ -628,6 +628,8 @@ en:
       leave_a_comment: "Leave a comment"
       login_to_leave_a_comment_html: "%{login_link} to leave a comment"
       login: "Log in"
+      previous_entry: "Previous Entry"
+      next_entry: "Next Entry"
     no_such_entry:
       title: "No such diary entry"
       heading: "No entry with the id: %{id}"

test/controllers/diary_entries_controller_test.rb

@@ -956,6 +956,47 @@ def test_unsubscribe_fail
     end
   end
 
+  def test_show_with_previous_and_next_links
+    user = create(:user)
+
+    entry1 = create(:diary_entry, :user => user)
+    entry2 = create(:diary_entry, :user => user)
+    entry3 = create(:diary_entry, :user => user)
+
+    get diary_entry_path(user.display_name, entry2)
+
+    assert_response :success
+
+    assert_select "nav.diary-entry-navigation a[href=?]", diary_entry_path(user.display_name, entry1)
+    assert_select "nav.diary-entry-navigation a[href=?]", diary_entry_path(user.display_name, entry3)
+  end
+
+  def test_show_without_previous_link_for_first_entry
+    user = create(:user)
+
+    entry1 = create(:diary_entry, :user => user)
+    entry2 = create(:diary_entry, :user => user)
+
+    get diary_entry_path(user.display_name, entry1)
+
+    assert_response :success
+
+    assert_select "nav.diary-entry-navigation a[href=?]", diary_entry_path(user.display_name, entry2)
+  end
+
+  def test_show_without_next_link_for_last_entry
+    user = create(:user)
+
+    entry1 = create(:diary_entry, :user => user)
+    entry2 = create(:diary_entry, :user => user)
+
+    get diary_entry_path(user.display_name, entry2)
+
+    assert_response :success
+
+    assert_select "nav.diary-entry-navigation a[href=?]", diary_entry_path(user.display_name, entry1)
+  end
+
   private
 
   def check_diary_index(*entries)