diff --git a/test/rdoc/end_to_end/heading_test.rb b/test/rdoc/end_to_end/heading_test.rb
new file mode 100644
index 0000000000..e7da9940e5
--- /dev/null
+++ b/test/rdoc/end_to_end/heading_test.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+require_relative 'helper'
+
+class HeadingTest < XrefTestCase
+
+  def test_headings
+    markup = <<MARKUP
+= Section 1
+== Section 1.1
+=== Section 1.1.1
+==== Section 1.1.1.1
+===== Section 1.1.1.1.1
+====== Section 1.1.1.1.1.1
+= Section 2
+== Section 2.1
+=== Section 2.1.1
+==== Section 2.1.1.1
+===== Section 2.1.1.1.1
+====== Section 2.1.1.1.1.1
+MARKUP
+    Helper.run_rdoc(markup, __method__) do |html_lines|
+      heading_lines = Helper.select_lines(html_lines, /^<h\d/)
+      # Check count of headings.
+      markup_lines = markup.lines
+      assert_equal(markup_lines.size, heading_lines.size)
+      # Check each markup line against the corresponding heading line.
+      markup_lines.each_with_index do |markup_line, index|
+        heading_line = heading_lines[index]
+        equal_signs, expected_title = markup_line.chomp.split(' ', 2)
+        assert(heading_line.include?(expected_title))
+        expected_heading_level = equal_signs.size
+        heading_line.match(/^<h(\d)/)
+        actual_heading_level = $1.to_i
+        assert_equal(expected_heading_level, actual_heading_level)
+      end
+    end
+  end
+
+end
diff --git a/test/rdoc/end_to_end/helper.rb b/test/rdoc/end_to_end/helper.rb
new file mode 100644
index 0000000000..01f483baea
--- /dev/null
+++ b/test/rdoc/end_to_end/helper.rb
@@ -0,0 +1,47 @@
+require 'fileutils'
+require 'open3'
+require_relative '../xref_test_case'
+
+class Helper
+
+  # Convenience method for selecting lines.
+  def self.select_lines(lines, pattern)
+    lines.select { |line| line.match(pattern) }
+  end
+
+  # Run rdoc for given markup; method is the caller's __method__, used for filename uniqueness.
+  def self.run_rdoc(markup, method)
+    # Make the temp dirpath; remove the dir and re-create it.
+    filestem = method.to_s
+    tmpdirpath = File.join(Dir.tmpdir, 'MarkupTest-' + filestem)
+    FileUtils.rm_rf(tmpdirpath)
+    Dir.mkdir(tmpdirpath)
+    FileUtils.chmod(0700, tmpdirpath)
+    # Do all the work in the temporary directory.
+    Dir.chdir(tmpdirpath) do
+      # Create the markdown file.
+      rdoc_filename = filestem + '.rdoc'
+      File.write(rdoc_filename, markup)
+      # Run rdoc, to create the HTML file.
+      command = "rdoc #{rdoc_filename + 'xxx'}"
+      puts command
+      Open3.popen3(command) do |_, stdout, stderr|
+        stdout_s = stdout.read
+        raise RuntimeError.new(stdout_s) unless stdout_s.match('Parsing')
+        stderr_s = stderr.read
+        raise RuntimeError.new(stderr_s) unless stderr_s.match('Generating')
+      end
+      # Get the HTML as lines.
+      html_filename = filestem + '_rdoc.html'
+      html_filepath = File.join('doc', html_filename)
+      html_lines = File.readlines(html_filepath)
+      # Yield them.
+      yield html_lines
+    end
+    # Clean up.
+    FileUtils.rm_rf(tmpdirpath)
+
+  end
+
+
+end
diff --git a/test/rdoc/end_to_end/horizontal_rule_test.rb b/test/rdoc/end_to_end/horizontal_rule_test.rb
new file mode 100644
index 0000000000..59bfa5bedd
--- /dev/null
+++ b/test/rdoc/end_to_end/horizontal_rule_test.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+require_relative 'helper'
+
+class HorizontalRuleTest < XrefTestCase
+
+  def test_horizontal_rule
+    markup = <<MARKUP
+---
+
+--- Not a horizontal rule.
+
+-- Not a horizontal rule.
+
+---
+
+MARKUP
+    Helper.run_rdoc(markup, __method__) do |html_lines|
+      # Check count of horizontal rules.
+      hr_lines = Helper.select_lines(html_lines, '<hr>')
+      assert_equal(2, hr_lines.size)
+      # Check count of not horizontal rules.
+      # One of the above generates an M-dash, the other an N-dash.
+      pattern = /<p>(—|–) Not a horizontal rule.<\/p>/
+      not_hr_lines = html_lines.select {|line| line.match(pattern) }
+      assert_equal(2, not_hr_lines.size)
+    end
+  end
+
+end
diff --git a/test/rdoc/end_to_end/text_markup_test.rb b/test/rdoc/end_to_end/text_markup_test.rb
new file mode 100644
index 0000000000..b0ebb55429
--- /dev/null
+++ b/test/rdoc/end_to_end/text_markup_test.rb
@@ -0,0 +1,149 @@
+# frozen_string_literal: true
+require_relative 'helper'
+
+class TextMarkupTest < XrefTestCase
+
+  def test_italic
+    markup = <<MARKUP
+
+Paragraph containing _italic_word_.
+
+>>>
+  Block quote containing _italic_word_.
+
+- List item containing _italic_word_.
+
+= Heading containing _italic_word_.
+
+Paragraph containing <i>italic phrase</i>.
+
+>>>
+  Block quote containing <i>italic phrase</i>.
+
+- List item containing <i>italic phrase</i>.
+
+= Heading containing <i>italic phrase</i>.
+
+Paragraph containing <em>italic phrase</em>.
+
+>>>
+  Block quote containing <em>italic phrase</em>.
+
+- List item containing <em>italic phrase</em>.
+
+= Heading containing <em>italic phrase</em>.
+
+MARKUP
+    Helper.run_rdoc(markup, __method__) do |html_lines|
+      italic_word_lines = Helper.select_lines(html_lines, '<em>italic_word</em>')
+      # Check count of italic words.
+      # (Five, not four, b/c the heading generates two.)
+      assert_equal(5, italic_word_lines.size)
+      italic_phrase_lines = Helper.select_lines(html_lines, '<em>italic phrase</em>')
+      # Check count of italic phrases.
+      # (Ten, not eight, b/c each heading generates two.)
+      assert_equal(10, italic_phrase_lines.size)
+    end
+  end
+
+  def test_bold
+    markup = <<MARKUP
+
+Paragraph containing *bold_word*.
+
+>>>
+  Block quote containing *bold_word*.
+
+- List item containing *bold_word*.
+
+= Heading containing *bold_word*.
+
+Paragraph containing <b>bold phrase</b>.
+
+>>>
+  Block quote containing <b>bold phrase</b>.
+
+- List item containing <b>bold phrase</b>.
+
+= Heading containing <b>bold phrase</b>.
+
+MARKUP
+    Helper.run_rdoc(markup, __method__) do |html_lines|
+      # Check count of bold words.
+      bold_word_lines = Helper.select_lines(html_lines, '<strong>bold_word</strong>')
+      # (Five, not four, b/c the heading generates two.)
+      assert_equal(5, bold_word_lines.size)
+      # Check count of bold phrases.
+      bold_phrase_lines = Helper.select_lines(html_lines, '<strong>bold phrase</strong>')
+      # (Five, not four, b/c the heading generates two.)
+      assert_equal(5, bold_phrase_lines.size)
+    end
+  end
+
+  def test_monofont
+    markup = <<MARKUP
+
+Paragraph containing +monofont_word+.
+
+>>>
+  Block quote containing +monofont_word+.
+
+- List item containing +monofont_word+.
+
+= Heading containing +monofont_word+.
+
+Paragraph containing <tt>monofont phrase</tt>.
+
+>>>
+  Block quote containing <tt>monofont phrase</tt>.
+
+- List item containing <tt>monofont phrase</tt>.
+
+= Heading containing <tt>monofont phrase</tt>.
+
+Paragraph containing <code>monofont phrase</code>.
+
+>>>
+  Block quote containing <code>monofont phrase</code>.
+
+- List item containing <code>monofont phrase</code>.
+
+= Heading containing <code>monofont phrase</code>.
+
+MARKUP
+    Helper.run_rdoc(markup, __method__) do |html_lines|
+      monofont_word_lines = Helper.select_lines(html_lines, '<code>monofont_word</code>')
+      # Check count of monofont words.
+      # (Five, not four, b/c the heading generates two.)
+      assert_equal(5, monofont_word_lines.size)
+      monofont_phrase_lines = Helper.select_lines(html_lines, '<code>monofont phrase</code>')
+      # Check count of monofont phrases.
+      # (Ten, not eight, b/c each heading generates two.)
+      assert_equal(10, monofont_phrase_lines.size)
+    end
+  end
+
+  def test_character_conversions
+    convertible_characters = %w[(c) (r) ... -- --- 'foo' "bar"].join(' ')
+
+    markup = <<MARKUP
+
+Paragraph containing #{convertible_characters}.
+
+>>>
+  Block quote containing #{convertible_characters}.
+
+- List item containing #{convertible_characters}.
+
+= Heading containing #{convertible_characters}.
+
+MARKUP
+    Helper.run_rdoc(markup, __method__) do |html_lines|
+      converted_character_lines = Helper.select_lines(html_lines, '© ® … – — ‘foo’ “bar”')
+      # Check count of converted character lines.
+      # (The generated heading line contains escapes, and so does not match.)
+      assert_equal(4, converted_character_lines.size)
+    end
+  end
+
+end