Add tests for news archives plugin

Provide tests that check the used layouts for news archive pages.

This targets issues like e.g. the one related to behavior changed
with Jekyll 4.2.0, fixed in f29a3d5.

Author: stomar

test/test_plugin_news.rb

@@ -0,0 +1,124 @@
+# frozen_string_literal: true
+
+require "helper"
+
+require "jekyll"
+require_relative "../_plugins/news"
+
+
+describe NewsArchivePlugin do
+
+  before do
+    chdir_tempdir
+
+    content = <<~CONFIG
+    CONFIG
+
+    create_file("source/_config.yml", content)
+
+    content = <<~LOCALES
+      month_names:
+        - January
+        - February
+
+      news:
+        recent_news: Recent News
+        yearly_archive_title: "%Y Archives"
+        monthly_archive_title: "%B %Y Archives"
+        yearly_archive_link: "%Y Archives"
+        monthly_archive_link: "%B %Y"
+    LOCALES
+
+    create_file("source/_data/locales/en.yml", content)
+
+    content = <<~LAYOUT
+      ---
+      layout: default
+      ---
+      NEWS LAYOUT
+
+      {% for post in page.posts %}
+        {{ post.title }}
+      {% endfor %}
+    LAYOUT
+
+    create_file("source/_layouts/news.html", content)
+
+    content = <<~LAYOUT
+      ---
+      layout: default
+      ---
+      NEWS ARCHIVE YEAR LAYOUT
+
+      {% for post in page.posts %}
+        {{ post.title }}
+      {% endfor %}
+    LAYOUT
+
+    create_file("source/_layouts/news_archive_year.html", content)
+
+    content = <<~LAYOUT
+      ---
+      layout: default
+      ---
+      NEWS ARCHIVE MONTH LAYOUT
+
+      {% for post in page.posts %}
+        {{ post.title }}
+      {% endfor %}
+    LAYOUT
+
+    create_file("source/_layouts/news_archive_month.html", content)
+
+    content = <<~POST
+      ---
+      title: "Post Jan 2020"
+      author: "stomar"
+      date: 2020-01-01 12:00:00 +0000
+      lang: en
+      ---
+
+      Content
+    POST
+
+    create_file("source/en/news/_posts/2020-01-01-post.md", content)
+
+    config = Jekyll.configuration(
+      source: "source",
+      destination: "_site",
+      quiet: true
+    )
+    site = Jekyll::Site.new(config)
+
+    file_wont_exist("_site")
+    site.process
+  end
+
+  after do
+    teardown_tempdir
+  end
+
+  it "should create news page" do
+    file_must_exist("_site/en/news/index.html")
+  end
+
+  it "should use the correct layout for news page" do
+    _(File.read("_site/en/news/index.html")).must_match "NEWS LAYOUT"
+  end
+
+  it "should create news/2020 page" do
+    file_must_exist("_site/en/news/2020/index.html")
+  end
+
+  it "should use the correct layout for news/2020 page" do
+    _(File.read("_site/en/news/2020/index.html")).must_match "YEAR LAYOUT"
+  end
+
+  it "should create news/2020/01 page" do
+    file_must_exist("_site/en/news/2020/index.html")
+  end
+
+  it "should use the correct layout for news/2020/01 page" do
+    _(File.read("_site/en/news/2020/01/index.html")).must_match "MONTH LAYOUT"
+  end
+end