Refactor markdown golden master specs

- See https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68671

ee/spec/fixtures/markdown/markdown_golden_master_examples.yml

+# See spec/fixtures/markdown/markdown_golden_master_examples.yml for documentation.
+---
+- name: attachment_link_for_group_wiki
+  api_context: group_wiki
+  substitutions:
+    # NOTE: We don't care about verifying specific attribute values here, that should be the
+    #       responsibility of unit tests. These tests are about the structure of the HTML.
+    path_attribute_id_substitution:
+      - regex: '(group|project)(\d+)'
+        replacement: '\1ID'
+  markdown: |-
+    [test-file](test-file.zip)
+  html: |-
+    <p data-sourcepos="1:1-1:26" dir="auto"><a href="/groups/group2/-/wikis/test-file.zip" data-canonical-src="test-file.zip">test-file</a></p>

ee/spec/frontend/content_editor/markdown_processing_spec.js

+import path from 'path';
+import {
+  createSharedExamples,
+  loadMarkdownApiExamples,
+} from 'jest/content_editor/markdown_processing_spec_helper';
+
+jest.mock('~/emoji');
+
+// See spec/fixtures/markdown/markdown_golden_master_examples.yml for documentation on how this spec works.
+describe('EE markdown processing in ContentEditor', () => {
+  // Ensure we generate same markdown that was provided to Markdown API.
+  const markdownYamlPath = path.join(
+    __dirname,
+    '..',
+    '..',
+    'fixtures',
+    'markdown',
+    'markdown_golden_master_examples.yml',
+  );
+  // eslint-disable-next-line jest/valid-describe
+  describe.each(loadMarkdownApiExamples(markdownYamlPath))('%s', createSharedExamples);
+});

ee/spec/frontend/fixtures/api_markdown.rb

-# frozen_string_literal: true
-
-require 'spec_helper'
-
-RSpec.describe API::MergeRequests, '(JavaScript fixtures)', type: :request do
-  include ApiHelpers
-  include WikiHelpers
-  include JavaScriptFixturesHelpers
-
-  let_it_be(:user) { create(:user) }
-
-  let_it_be(:group) { create(:group, :public) }
-
-  let_it_be(:group_wiki) { create(:group_wiki, user: user) }
-
-  let(:group_wiki_page) { create(:wiki_page, wiki: group_wiki) }
-  let(:project_wiki_page) { create(:wiki_page, wiki: project_wiki) }
-
-  before(:all) do
-    group.add_owner(user)
-  end
-
-  before do
-    stub_group_wikis(true)
-    sign_in(user)
-  end
-
-  markdown_examples = begin
-    yaml_file_path = File.expand_path('api_markdown.yml', __dir__)
-    yaml = File.read(yaml_file_path)
-    YAML.safe_load(yaml, symbolize_names: true)
-  end
-
-  markdown_examples.each do |markdown_example|
-    context = markdown_example.fetch(:context, '')
-    name = markdown_example.fetch(:name)
-
-    context "for #{name}#{!context.empty? ? " (context: #{context})" : ''}" do
-      let(:markdown) { markdown_example.fetch(:markdown) }
-
-      name = "#{context}_#{name}" unless context.empty?
-
-      it "api/markdown/#{name}.json" do
-        api_url = case context
-                  when 'group_wiki'
-                    "/groups/#{group.full_path}/-/wikis/#{group_wiki_page.slug}/preview_markdown"
-                  else
-                    api "/markdown"
-                  end
-
-        post api_url, params: { text: markdown, gfm: true }
-        expect(response).to be_successful
-      end
-    end
-  end
-end

ee/spec/frontend/fixtures/api_markdown.yml

-# This data file drives the specs in
-# ee/spec/frontend/fixtures/api_markdown.rb and
----
-- name: attachment_link
-  context: group_wiki
-  markdown: '[test-file](test-file.zip)'

ee/spec/requests/api/markdown_golden_master_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+# See spec/fixtures/markdown/markdown_golden_master_examples.yml for documentation on how this spec works.
+RSpec.describe API::Markdown, 'EE Golden Master' do
+  include WikiHelpers
+
+  let_it_be(:user) { create(:user, username: 'gfm_ee_user') }
+
+  let_it_be(:group_wiki) { create(:group_wiki, user: user) }
+
+  let_it_be(:group_wiki_page) { create(:wiki_page, wiki: group_wiki) }
+
+  before do
+    stub_group_wikis(true)
+    sign_in(user)
+  end
+
+  markdown_yml_file_path = File.expand_path('../../fixtures/markdown/markdown_golden_master_examples.yml', __dir__)
+  include_examples 'API::Markdown Golden Master shared context', markdown_yml_file_path do
+    extend ::Gitlab::Utils::Override
+
+    override :supported_api_contexts
+    def supported_api_contexts
+      super + %w(group_wiki)
+    end
+
+    override :get_url_for_api_context
+    def get_url_for_api_context(api_context)
+      case api_context
+      when 'group_wiki'
+        "/groups/#{group.full_path}/-/wikis/#{group_wiki_page.slug}/preview_markdown"
+      else
+        super
+      end
+    end
+  end
+end

spec/fixtures/markdown/markdown_golden_master_examples.yml

+# Related Specs:
+#
+# This data file drives the specs in the following specs:
+#
+# CE Backend:  spec/requests/api/markdown_golden_master_spec.rb
+# CE Frontend: spec/frontend/content_editor/markdown_processing_spec.js
+#
+# For EE, these files are used:
+# EE Data:     ee/spec/fixtures/markdown/markdown_golden_master_examples.yml
+# EE Backend:  ee/spec/requests/api/markdown_golden_master_spec.rb
+# EE Frontend: ee/spec/frontend/content_editor/markdown_processing_spec.js
+#
+#
+# Requirements:
+#
+# 1. Frontend: We should have test coverage that the Content Editor can properly serialize HTML
+#    to Markdown for all GFM source elements which it currently supports.
+# 2. Frontend: We should have test coverage that the Content Editor can properly render the expected
+#    HTML for all GFM source elements which it currently supports (not currently implemented in the
+#    frontend - this will likely be a standalone module outside of the Content Editor).
+# 3. Backend: We should ensure that for all GFM elements, the backend always renders the expected
+#    HTML, for **all** supported GFM source elements.
+#
+# If any of this this ever changes unexpectedly, tests will start failing, and force the same change
+# to be made on the backend and frontend.
+#
+#
+# Overview:
+#
+# These specs ensure that the bidirectional Markdown <-> HTML conversion logic is implemented
+# identically on the backend and frontend, for all supported GitLab-Flavored Markdown examples, by
+# running hardcoded examples through the logic and ensuring the results match.
+#
+# This is an example of the "Golden Master Testing" approach, which is also referred to as
+# "Approval Testing" or "Characterization Testing".
+#
+# The term "Golden Master" originally comes from the recording industry, and refers to process
+# of "mastering", or making a final mix from which all other copies will be produced.
+#
+# See:
+# - https://en.wikipedia.org/wiki/Characterization_test
+# - https://en.wikipedia.org/wiki/Gold_master_(disambiguation)
+#
+#
+# What we are doing is actually a type Golden Master testing with modifications:
+#
+# 1. The original markdown examples used to drive the tests are taken from this YAML, and can be
+#    considered a form of "fixture" in this case.
+# 2. The HTML in the YAML is the "Golden Master", but we are going to use it to assert
+#    against **TWO** different implementations of markdown rendering:
+#    1. The frontend, implemented as Jest specs.
+#       1. This will assert both HTML -> markdown serialization (what it currently does), as well as...
+#       2. Markdown -> HTML rendering (not currently implemented in the frontend - this will likely
+#          be a standalone module outside of the Content Editor)
+#    1. The backend, implemented as requests specs
+#       1. This will assert markdown -> HTML conversion by the backend.
+#
+# Also see the MR for more explanation on the details of this approach:
+#   https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68671
+#
+#
+# Usage:
+#
+# * Please keep this file alphabetized.
+# * To run focused example(s), set the `FOCUSED_MARKDOWN_EXAMPLES` environment variable to a
+#   comma-separated list of example names. This works for the frontend and backend specs.
+# * Required attributes for every example:
+#   1. `name`: Specifies the Name of the example, which will be printed when specs are run.
+#   2. `markdown`: Specifies the Markdown for the example, which will be compared with the
+#      Markdown the code generates from the corresponding specified HTML.
+#   3. `html`: Specifies the HTML for the example, which will be compared with the
+#      HTML the code generated from the corresponding specified Markdown.
+# * `api_context` (optional): This is used when a single markdown can be
+#   rendered differently depending on the API endpoint or area of the app from which it is called or
+#   used. The valid values for `api_context` are: `project`, `group`, `project_wiki`,
+#   and (for EE only) `group_wiki`.The `name` attribute must also have a `_for_[API_CONTEXT]` suffix
+#   which matches the `api_context`, in order to ensure that each example has a unique `name`
+#   identifier. For example, `attachment_image_for_project`.
+# * `pending`: To skip an example that is broken or not yet fully implemented, add
+#   a `pending: <reason with issue/MR URL>` attribute to the example. See
+#   the `a_example_of_pending` entry for an example.
+# * `pending` with key: You can also mark an example pending on only the frontend or backend. See
+#   the `a_example_of_pending_with_keys` entry for an example.
+# * `substitutions`: For examples which may have variable content in different environments,
+#   such as portions of the URI, or database record IDs, you can specify
+#   `substitutions`, which is an array of regex/replacement pairs. The HTML
+#   value will be normalized with each of these pairs using Ruby `gsub`
+#   before comparing.
+#   The substitution values can (and are) also reused in multiple examples
+#   via YAML anchors.
+#
+#
+# Notes:
+#
+# * The html values should exactly match what the backend markdown API endpoints return for the
+#   given markdown example. The HTML is intentionally not indented, formatted, or split across lines.
+#   This is a bit less readable, but it makes the spec logic simpler and less error prone for edge
+#   cases.
+#
+#
+# Debugging Failures and Writing New Entries:
+#
+# * You need to compare what is different between the expected and actual values.
+# * In rspec, the diff printed out includes the full text of the HTML. This may be long, so you
+#   may want to turn line wrapping on or off or copy the diff to separate file(s) for easier comparison.
+# * If the difference is just in an attribute value, use the `substitutions` support to normalize
+#   the HTML before comparing. These specs are only validating the HTML structure, the individual
+#   markdown elements' unit tests can provide coverage that the exact attribute values are correct.
+# * If you are making a new entry, you can create the entry according to the `Usage` section above,
+#   but leave the `html` value blank. This will cause the spec to fail, and you can fill in the
+#   `html` value based on the spec failure that is printed out.
+
+---
+
+#- name: an_example_of_pending
+#  pending: 'This is an example of the pending attribute: http://example.com'
+#  markdown: ;)
+#  html: |-
+#    <blink data-sourcepos="1:1-1:2"/></blink>
+#
+
+#- name: an_example_of_pending_with_keys
+#  pending:
+#    frontend: 'This is an example of the frontend-only pending attribute: http://example.com'
+#    backend: 'This is an example of the backend-only pending attribute: http://example.com'
+#  markdown: ;)
+#  html: |-
+#    <blink data-sourcepos="1:1-1:2"/></blink>
+
+- name: attachment_image_for_group
+  api_context: group
+  substitutions:
+    # Note: having the top level `substitutions` data structure be a hash of arrays
+    # allows us to compose multiple substitutions via YAML anchors (YAML anchors
+    # pointing to arrays can't be combined)
+    uri_substitution: &uri_substitution
+      # NOTE: We don't care about verifying specific attribute values here, that should be the
+      #       responsibility of unit tests. These tests are about the structure of the HTML.
+      - regex: '(href|data-src)(=")(.*?)(test-file\.(png|zip)")'
+        replacement: '\1\2URI_PREFIX\4'
+  markdown: |-
+    ![test-file](/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png)
+  html: |-
+    <p data-sourcepos="1:1-1:69" dir="auto"><a class="no-attachment-icon gfm" href="/groups/group58/-/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png" target="_blank" rel="noopener noreferrer" data-canonical-src="/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png" data-link="true"><img src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" alt="test-file" class="lazy gfm" data-src="/groups/group58/-/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png" data-canonical-src="/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png"></a></p>
+
+- name: attachment_image_for_project
+  api_context: project
+  substitutions:
+    uri_substitution: *uri_substitution
+  markdown: |-
+    ![test-file](/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png)
+  html: |-
+    <p data-sourcepos="1:1-1:69" dir="auto"><a class="no-attachment-icon gfm" href="/group58/project22/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png" target="_blank" rel="noopener noreferrer" data-canonical-src="/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png" data-link="true"><img src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" alt="test-file" class="lazy gfm" data-src="/group58/project22/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png" data-canonical-src="/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png"></a></p>
+
+- name: attachment_image_for_project_wiki
+  api_context: project_wiki
+  substitutions:
+    uri_substitution: *uri_substitution
+  markdown: |-
+    ![test-file](test-file.png)
+  html: |-
+    <p data-sourcepos="1:1-1:27" dir="auto"><a class="no-attachment-icon" href="/group1/project1/-/wikis/test-file.png" target="_blank" rel="noopener noreferrer" data-canonical-src="test-file.png"><img alt="test-file" class="lazy" data-src="/group1/project1/-/wikis/test-file.png" data-canonical-src="test-file.png"></a></p>
+
+- name: attachment_link_for_group
+  api_context: group
+  substitutions:
+    uri_substitution: *uri_substitution
+  markdown: |-
+    [test-file](/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.zip)
+  html: |-
+    <p data-sourcepos="1:1-1:68" dir="auto"><a href="/groups/group58/-/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.zip" data-canonical-src="/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.zip" data-link="true" class="gfm">test-file</a></p>
+
+- name: attachment_link_for_project
+  api_context: project
+  substitutions:
+    uri_substitution: *uri_substitution
+  markdown: |-
+    [test-file](/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.zip)
+  html: |-
+    <p data-sourcepos="1:1-1:68" dir="auto"><a href="/group58/project22/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.zip" data-canonical-src="/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.zip" data-link="true" class="gfm">test-file</a></p>
+
+- name: attachment_link_for_project_wiki
+  api_context: project_wiki
+  substitutions:
+    uri_substitution: *uri_substitution
+  # TODO: The current frontend example doesn't include the path, need to look into why it does after refactoring to the new golden master approach
+  pending:
+    frontend: 'The current frontend example doesnt include the path, need to look into why it does after refactoring to the new golden master approach'
+  markdown: |-
+    [test-file](test-file.zip)
+  html: |-
+    <p data-sourcepos="1:1-1:26" dir="auto"><a href="/group1/project1/-/wikis/test-file.zip" data-canonical-src="test-file.zip">test-file</a></p>
+
+- name: audio
+  markdown: |-
+    ![Sample Audio](https://gitlab.com/gitlab.mp3)
+  html: |-
+    <p data-sourcepos="1:1-1:46" dir="auto"><span class="media-container audio-container"><audio src="https://gitlab.com/gitlab.mp3" controls="true" data-setup="{}" data-title="Sample Audio"></audio><a href="https://gitlab.com/gitlab.mp3" target="_blank" rel="nofollow noreferrer noopener" title="Download 'Sample Audio'">Sample Audio</a></span></p>
+
+- name: audio_and_video_in_lists
+  markdown: |-
+    * ![Sample Audio](https://gitlab.com/1.mp3)
+    * ![Sample Video](https://gitlab.com/2.mp4)
+
+    1. ![Sample Video](https://gitlab.com/1.mp4)
+    2. ![Sample Audio](https://gitlab.com/2.mp3)
+
+    * [x] ![Sample Audio](https://gitlab.com/1.mp3)
+    * [x] ![Sample Audio](https://gitlab.com/2.mp3)
+    * [x] ![Sample Video](https://gitlab.com/3.mp4)
+  html: |-
+    <ul data-sourcepos="1:1-3:0" dir="auto">
+    <li data-sourcepos="1:1-1:43"><span class="media-container audio-container"><audio src="https://gitlab.com/1.mp3" controls="true" data-setup="{}" data-title="Sample Audio"></audio><a href="https://gitlab.com/1.mp3" target="_blank" rel="nofollow noreferrer noopener" title="Download 'Sample Audio'">Sample Audio</a></span></li>
+    <li data-sourcepos="2:1-3:0"><span class="media-container video-container"><video src="https://gitlab.com/2.mp4" controls="true" data-setup="{}" data-title="Sample Video" width="400" preload="metadata"></video><a href="https://gitlab.com/2.mp4" target="_blank" rel="nofollow noreferrer noopener" title="Download 'Sample Video'">Sample Video</a></span></li>
+    </ul>
+    <ol data-sourcepos="4:1-6:0" dir="auto">
+    <li data-sourcepos="4:1-4:44"><span class="media-container video-container"><video src="https://gitlab.com/1.mp4" controls="true" data-setup="{}" data-title="Sample Video" width="400" preload="metadata"></video><a href="https://gitlab.com/1.mp4" target="_blank" rel="nofollow noreferrer noopener" title="Download 'Sample Video'">Sample Video</a></span></li>
+    <li data-sourcepos="5:1-6:0"><span class="media-container audio-container"><audio src="https://gitlab.com/2.mp3" controls="true" data-setup="{}" data-title="Sample Audio"></audio><a href="https://gitlab.com/2.mp3" target="_blank" rel="nofollow noreferrer noopener" title="Download 'Sample Audio'">Sample Audio</a></span></li>
+    </ol>
+    <ul data-sourcepos="7:1-9:47" class="task-list" dir="auto">
+    <li data-sourcepos="7:1-7:47" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> <span class="media-container audio-container"><audio src="https://gitlab.com/1.mp3" controls="true" data-setup="{}" data-title="Sample Audio"></audio><a href="https://gitlab.com/1.mp3" target="_blank" rel="nofollow noreferrer noopener" title="Download 'Sample Audio'">Sample Audio</a></span>
+    </li>
+    <li data-sourcepos="8:1-8:47" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> <span class="media-container audio-container"><audio src="https://gitlab.com/2.mp3" controls="true" data-setup="{}" data-title="Sample Audio"></audio><a href="https://gitlab.com/2.mp3" target="_blank" rel="nofollow noreferrer noopener" title="Download 'Sample Audio'">Sample Audio</a></span>
+    </li>
+    <li data-sourcepos="9:1-9:47" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> <span class="media-container video-container"><video src="https://gitlab.com/3.mp4" controls="true" data-setup="{}" data-title="Sample Video" width="400" preload="metadata"></video><a href="https://gitlab.com/3.mp4" target="_blank" rel="nofollow noreferrer noopener" title="Download 'Sample Video'">Sample Video</a></span>
+    </li>
+    </ul>
+
+- name: blockquote
+  markdown: |-
+    > This is a blockquote
+    >
+    > This is another one
+  html: |-
+    <blockquote data-sourcepos="1:1-3:21" dir="auto">
+    <p data-sourcepos="1:3-1:22">This is a blockquote</p>
+    <p data-sourcepos="3:3-3:21">This is another one</p>
+    </blockquote>
+
+- name: bold
+  markdown: |-
+    **bold**
+  html: |-
+    <p data-sourcepos="1:1-1:8" dir="auto"><strong>bold</strong></p>
+
+- name: bullet_list_style_1
+  markdown: |-
+    * list item 1
+    * list item 2
+      * embedded list item 3
+  html: |-
+    <ul data-sourcepos="1:1-3:24" dir="auto">
+    <li data-sourcepos="1:1-1:13">list item 1</li>
+    <li data-sourcepos="2:1-3:24">list item 2
+    <ul data-sourcepos="3:3-3:24">
+    <li data-sourcepos="3:3-3:24">embedded list item 3</li>
+    </ul>
+    </li>
+    </ul>
+
+- name: bullet_list_style_2
+  markdown: |-
+    - list item 1
+    - list item 2
+      * embedded list item 3
+  html: |-
+    <ul data-sourcepos="1:1-3:24" dir="auto">
+    <li data-sourcepos="1:1-1:13">list item 1</li>
+    <li data-sourcepos="2:1-3:24">list item 2
+    <ul data-sourcepos="3:3-3:24">
+    <li data-sourcepos="3:3-3:24">embedded list item 3</li>
+    </ul>
+    </li>
+    </ul>
+
+- name: bullet_list_style_3
+  markdown: |-
+    + list item 1
+    + list item 2
+      - embedded list item 3
+  html: |-
+    <ul data-sourcepos="1:1-3:24" dir="auto">
+    <li data-sourcepos="1:1-1:13">list item 1</li>
+    <li data-sourcepos="2:1-3:24">list item 2
+    <ul data-sourcepos="3:3-3:24">
+    <li data-sourcepos="3:3-3:24">embedded list item 3</li>
+    </ul>
+    </li>
+    </ul>
+
+- name: code_block
+  markdown: |-
+    ```javascript
+      console.log('hello world')
+    ```
+  html: |-
+    <pre data-sourcepos="1:1-3:3" class="code highlight js-syntax-highlight language-javascript" lang="javascript" v-pre="true"><code><span id="LC1" class="line" lang="javascript">  <span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="dl">'</span><span class="s1">hello world</span><span class="dl">'</span><span class="p">)</span></span></code></pre>
+
+- name: color_chips
+  markdown: |-
+    - `#F00`
+    - `#F00A`
+    - `#FF0000`
+    - `#FF0000AA`
+    - `RGB(0,255,0)`
+    - `RGB(0%,100%,0%)`
+    - `RGBA(0,255,0,0.3)`
+    - `HSL(540,70%,50%)`
+    - `HSLA(540,70%,50%,0.3)`
+  html: |-
+    <ul data-sourcepos="1:1-9:25" dir="auto">
+    <li data-sourcepos="1:1-1:8"><code>#F00<span class="gfm-color_chip"><span style="background-color: #F00;"></span></span></code></li>
+    <li data-sourcepos="2:1-2:9"><code>#F00A<span class="gfm-color_chip"><span style="background-color: #F00A;"></span></span></code></li>
+    <li data-sourcepos="3:1-3:11"><code>#FF0000<span class="gfm-color_chip"><span style="background-color: #FF0000;"></span></span></code></li>
+    <li data-sourcepos="4:1-4:13"><code>#FF0000AA<span class="gfm-color_chip"><span style="background-color: #FF0000AA;"></span></span></code></li>
+    <li data-sourcepos="5:1-5:16"><code>RGB(0,255,0)<span class="gfm-color_chip"><span style="background-color: RGB(0,255,0);"></span></span></code></li>
+    <li data-sourcepos="6:1-6:19"><code>RGB(0%,100%,0%)<span class="gfm-color_chip"><span style="background-color: RGB(0%,100%,0%);"></span></span></code></li>
+    <li data-sourcepos="7:1-7:21"><code>RGBA(0,255,0,0.3)<span class="gfm-color_chip"><span style="background-color: RGBA(0,255,0,0.3);"></span></span></code></li>
+    <li data-sourcepos="8:1-8:20"><code>HSL(540,70%,50%)<span class="gfm-color_chip"><span style="background-color: HSL(540,70%,50%);"></span></span></code></li>
+    <li data-sourcepos="9:1-9:25"><code>HSLA(540,70%,50%,0.3)<span class="gfm-color_chip"><span style="background-color: HSLA(540,70%,50%,0.3);"></span></span></code></li>
+    </ul>
+
+- name: description_list
+  markdown: |-
+    <dl>
+    <dt>Frog</dt>
+    <dd>Wet green thing</dd>
+    <dt>Rabbit</dt>
+    <dd>Warm fluffy thing</dd>
+    <dt>Punt</dt>
+    <dd>Kick a ball</dd>
+    <dd>Take a bet</dd>
+    <dt>Color</dt>
+    <dt>Colour</dt>
+    <dd>
+
+    Any hue except _white_ or **black**
+
+    </dd>
+    </dl>
+  html: |-
+    <dl>
+    <dt>Frog</dt>
+    <dd>Wet green thing</dd>
+    <dt>Rabbit</dt>
+    <dd>Warm fluffy thing</dd>
+    <dt>Punt</dt>
+    <dd>Kick a ball</dd>
+    <dd>Take a bet</dd>
+    <dt>Color</dt>
+    <dt>Colour</dt>
+    <dd>
+    <p data-sourcepos="13:1-13:35">Any hue except <em>white</em> or <strong>black</strong></p>
+    </dd>
+    </dl>
+
+- name: details
+  markdown: |-
+    <details>
+    <summary>This is the visible summary of the collapsible section</summary>
+
+    1. collapsed markdown
+    2. more collapsed markdown
+
+    </details>
+  html: |-
+    <details>
+    <summary>This is the visible summary of the collapsible section</summary>
+    <ol data-sourcepos="4:1-6:0">
+    <li data-sourcepos="4:1-4:21">collapsed markdown</li>
+    <li data-sourcepos="5:1-6:0">more collapsed markdown</li>
+    </ol>
+    </details>
+
+- name: div
+  markdown: |-
+    <div>plain text</div>
+    <div>
+
+    just a plain ol' div, not much to _expect_!
+
+    </div>
+  html: |-
+    <div>plain text</div>
+    <div>
+    <p data-sourcepos="4:1-4:43">just a plain ol' div, not much to <em>expect</em>!</p>
+    </div>
+
+- name: emoji
+  markdown: |-
+    :sparkles: :heart: :100:
+  html: |-
+    <p data-sourcepos="1:1-1:24" dir="auto"><gl-emoji title="sparkles" data-name="sparkles" data-unicode-version="6.0">✨</gl-emoji> <gl-emoji title="heavy black heart" data-name="heart" data-unicode-version="1.1">❤</gl-emoji> <gl-emoji title="hundred points symbol" data-name="100" data-unicode-version="6.0">💯</gl-emoji></p>
+
+- name: emphasis
+  markdown: _emphasized text_
+  html: <p data-sourcepos="1:1-1:17" dir="auto"><em>emphasized text</em></p>
+
+- name: figure
+  markdown: |-
+    <figure>
+
+    ![Elephant at sunset](elephant-sunset.jpg)
+
+    <figcaption>An elephant at sunset</figcaption>
+    </figure>
+    <figure>
+
+    ![A crocodile wearing crocs](croc-crocs.jpg)
+
+    <figcaption>
+
+    A crocodile wearing _crocs_!
+
+    </figcaption>
+    </figure>
+  html: |-
+    <figure>
+    <p data-sourcepos="3:1-3:42"><a class="no-attachment-icon" href="elephant-sunset.jpg" target="_blank" rel="noopener noreferrer"><img src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" alt="Elephant at sunset" class="lazy" data-src="elephant-sunset.jpg"></a></p>
+    <figcaption>An elephant at sunset</figcaption>
+    </figure>
+    <figure>
+    <p data-sourcepos="9:1-9:44"><a class="no-attachment-icon" href="croc-crocs.jpg" target="_blank" rel="noopener noreferrer"><img src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" alt="A crocodile wearing crocs" class="lazy" data-src="croc-crocs.jpg"></a></p>
+    <figcaption>
+    <p data-sourcepos="13:1-13:28">A crocodile wearing <em>crocs</em>!</p>
+    </figcaption>
+    </figure>
+
+- name: frontmatter_json
+  markdown: |-
+    ;;;
+    {
+      "title": "Page title"
+    }
+    ;;;
+  html: |-
+    <pre data-sourcepos="1:1-5:3" class="code highlight js-syntax-highlight language-json" lang="json" data-lang-params="frontmatter" v-pre="true"><code><span id="LC1" class="line" lang="json"><span class="p">{</span></span>
+    <span id="LC2" class="line" lang="json"><span class="w">  </span><span class="nl">"title"</span><span class="p">:</span><span class="w"> </span><span class="s2">"Page title"</span></span>
+    <span id="LC3" class="line" lang="json"><span class="p">}</span></span></code></pre>
+
+- name: frontmatter_toml
+  markdown: |-
+    +++
+    title = "Page title"
+    +++
+  html: <pre data-sourcepos="1:1-3:3" class="code highlight js-syntax-highlight language-toml" lang="toml" data-lang-params="frontmatter" v-pre="true"><code><span id="LC1" class="line" lang="toml"><span class="py">title</span> <span class="p">=</span> <span class="s">"Page title"</span></span></code></pre>
+
+- name: frontmatter_yaml
+  markdown: |-
+    ---
+    title: Page title
+    ---
+  html: <pre data-sourcepos="1:1-3:3" class="code highlight js-syntax-highlight language-yaml" lang="yaml" data-lang-params="frontmatter" v-pre="true"><code><span id="LC1" class="line" lang="yaml"><span class="na">title</span><span class="pi">:</span> <span class="s">Page title</span></span></code></pre>
+
+- name: hard_break
+  markdown: |-
+    This is a line after a\
+    hard break
+  html: |-
+    <p data-sourcepos="1:1-2:10" dir="auto">This is a line after a<br>
+    hard break</p>
+
+- name: headings
+  markdown: |-
+    # Heading 1
+
+    ## Heading 2
+
+    ### Heading 3
+
+    #### Heading 4
+
+    ##### Heading 5
+
+    ###### Heading 6
+  html: |-
+    <h1 data-sourcepos="1:1-1:11" dir="auto">
+    <a id="user-content-heading-1" class="anchor" href="#heading-1" aria-hidden="true"></a>Heading 1</h1>
+    <h2 data-sourcepos="3:1-3:12" dir="auto">
+    <a id="user-content-heading-2" class="anchor" href="#heading-2" aria-hidden="true"></a>Heading 2</h2>
+    <h3 data-sourcepos="5:1-5:13" dir="auto">
+    <a id="user-content-heading-3" class="anchor" href="#heading-3" aria-hidden="true"></a>Heading 3</h3>
+    <h4 data-sourcepos="7:1-7:14" dir="auto">
+    <a id="user-content-heading-4" class="anchor" href="#heading-4" aria-hidden="true"></a>Heading 4</h4>
+    <h5 data-sourcepos="9:1-9:15" dir="auto">
+    <a id="user-content-heading-5" class="anchor" href="#heading-5" aria-hidden="true"></a>Heading 5</h5>
+    <h6 data-sourcepos="11:1-11:16" dir="auto">
+    <a id="user-content-heading-6" class="anchor" href="#heading-6" aria-hidden="true"></a>Heading 6</h6>
+
+- name: horizontal_rule
+  markdown: |-
+    ---
+  html: |-
+    <hr data-sourcepos="1:1-1:3">
+
+- name: html_marks
+  markdown: |-
+    * Content editor is ~~great~~<ins>amazing</ins>.
+    * If the changes <abbr title="Looks good to merge">LGTM</abbr>, please <abbr title="Merge when pipeline succeeds">MWPS</abbr>.
+    * The English song <q>Oh I do like to be beside the seaside</q> looks like this in Hebrew: <span dir="rtl">אה, אני אוהב להיות ליד חוף הים</span>. In the computer's memory, this is stored as <bdo dir="ltr">אה, אני אוהב להיות ליד חוף הים</bdo>.
+    * <cite>The Scream</cite> by Edvard Munch. Painted in 1893.
+    * <dfn>HTML</dfn> is the standard markup language for creating web pages.
+    * Do not forget to buy <mark>milk</mark> today.
+    * This is a paragraph and <small>smaller text goes here</small>.
+    * The concert starts at <time datetime="20:00">20:00</time> and you'll be able to enjoy the band for at least <time datetime="PT2H30M">2h 30m</time>.
+    * Press <kbd>Ctrl</kbd> + <kbd>C</kbd> to copy text (Windows).
+    * WWF's goal is to: <q>Build a future where people live in harmony with nature.</q> We hope they succeed.
+    * The error occured was: <samp>Keyboard not found. Press F1 to continue.</samp>
+    * The area of a triangle is: 1/2 x <var>b</var> x <var>h</var>, where <var>b</var> is the base, and <var>h</var> is the vertical height.
+    * <ruby>漢<rt>ㄏㄢˋ</rt></ruby>
+    * C<sub>7</sub>H<sub>16</sub> + O<sub>2</sub> → CO<sub>2</sub> + H<sub>2</sub>O
+    * The **Pythagorean theorem** is often expressed as <var>a<sup>2</sup></var> + <var>b<sup>2</sup></var> = <var>c<sup>2</sup></var>
+  html: |-
+    <ul data-sourcepos="1:1-15:130" dir="auto">
+    <li data-sourcepos="1:1-1:48">Content editor is <del>great</del><ins>amazing</ins>.</li>
+    <li data-sourcepos="2:1-2:126">If the changes <abbr title="Looks good to merge">LGTM</abbr>, please <abbr title="Merge when pipeline succeeds">MWPS</abbr>.</li>
+    <li data-sourcepos="3:1-3:288">The English song <q>Oh I do like to be beside the seaside</q> looks like this in Hebrew: <span dir="rtl">אה, אני אוהב להיות ליד חוף הים</span>. In the computer's memory, this is stored as <bdo dir="ltr">אה, אני אוהב להיות ליד חוף הים</bdo>.</li>
+    <li data-sourcepos="4:1-4:59">
+    <cite>The Scream</cite> by Edvard Munch. Painted in 1893.</li>
+    <li data-sourcepos="5:1-5:73">
+    <dfn>HTML</dfn> is the standard markup language for creating web pages.</li>
+    <li data-sourcepos="6:1-6:47">Do not forget to buy <mark>milk</mark> today.</li>
+    <li data-sourcepos="7:1-7:64">This is a paragraph and <small>smaller text goes here</small>.</li>
+    <li data-sourcepos="8:1-8:149">The concert starts at <time datetime="20:00">20:00</time> and you'll be able to enjoy the band for at least <time datetime="PT2H30M">2h 30m</time>.</li>
+    <li data-sourcepos="9:1-9:62">Press <kbd>Ctrl</kbd> + <kbd>C</kbd> to copy text (Windows).</li>
+    <li data-sourcepos="10:1-10:105">WWF's goal is to: <q>Build a future where people live in harmony with nature.</q> We hope they succeed.</li>
+    <li data-sourcepos="11:1-11:79">The error occured was: <samp>Keyboard not found. Press F1 to continue.</samp>
+    </li>
+    <li data-sourcepos="12:1-12:136">The area of a triangle is: 1/2 x <var>b</var> x <var>h</var>, where <var>b</var> is the base, and <var>h</var> is the vertical height.</li>
+    <li data-sourcepos="13:1-13:35"><ruby>漢<rt>ㄏㄢˋ</rt></ruby></li>
+    <li data-sourcepos="14:1-14:81">C<sub>7</sub>H<sub>16</sub> + O<sub>2</sub> → CO<sub>2</sub> + H<sub>2</sub>O</li>
+    <li data-sourcepos="15:1-15:130">The <strong>Pythagorean theorem</strong> is often expressed as <var>a<sup>2</sup></var> + <var>b<sup>2</sup></var> = <var>c<sup>2</sup></var>
+    </li>
+    </ul>
+
+- name: image
+  markdown: |-
+    ![alt text](https://gitlab.com/logo.png)
+  html: |-
+    <p data-sourcepos="1:1-1:40" dir="auto"><a class="no-attachment-icon" href="https://gitlab.com/logo.png" target="_blank" rel="nofollow noreferrer noopener"><img src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" alt="alt text" class="lazy" data-src="https://gitlab.com/logo.png"></a></p>
+
+- name: inline_code
+  markdown: |-
+    `code`
+  html: |-
+    <p data-sourcepos="1:1-1:6" dir="auto"><code>code</code></p>
+
+- name: inline_diff
+  markdown: |-
+    * {-deleted-}
+    * {+added+}
+  html: |-
+    <ul data-sourcepos="1:1-2:11" dir="auto">
+    <li data-sourcepos="1:1-1:13"><span class="idiff left right deletion">deleted</span></li>
+    <li data-sourcepos="2:1-2:11"><span class="idiff left right addition">added</span></li>
+    </ul>
+
+- name: label
+  pending:
+    # TODO: There is an error with the frontend HTML to markdown spec adding a double escape (\\) to the label tilde.
+    frontend: 'There is an error with the frontend HTML to markdown spec adding a double escape (\\) to the label tilde.'
+  markdown: |-
+    ~bug
+  html: |-
+    <p data-sourcepos="1:1-1:4" dir="auto">~bug</p>
+
+- name: link
+  markdown: |-
+    [GitLab](https://gitlab.com)
+  html: |-
+    <p data-sourcepos="1:1-1:28" dir="auto"><a href="https://gitlab.com" rel="nofollow noreferrer noopener" target="_blank">GitLab</a></p>
+
+- name: math
+  markdown: |-
+    This math is inline $`a^2+b^2=c^2`$.
+
+    This is on a separate line:
+
+    ```math
+    a^2+b^2=c^2
+    ```
+  html: |-
+    <p data-sourcepos="1:1-1:36" dir="auto">This math is inline <code class="code math js-render-math" data-math-style="inline">a^2+b^2=c^2</code>.</p>
+    <p data-sourcepos="3:1-3:27" dir="auto">This is on a separate line:</p>
+    <pre data-sourcepos="5:1-7:3" class="code highlight js-syntax-highlight language-math js-render-math" lang="math" v-pre="true" data-math-style="display"><code><span id="LC1" class="line" lang="math">a^2+b^2=c^2</span></code></pre>
+
+- name: ordered_list
+  markdown: |-
+    1. list item 1
+    2. list item 2
+    3. list item 3
+  html: |-
+    <ol data-sourcepos="1:1-3:14" dir="auto">
+    <li data-sourcepos="1:1-1:14">list item 1</li>
+    <li data-sourcepos="2:1-2:14">list item 2</li>
+    <li data-sourcepos="3:1-3:14">list item 3</li>
+    </ol>
+
+- name: ordered_list_with_start_order
+  markdown: |-
+    134. list item 1
+    135. list item 2
+    136. list item 3
+  html: |-
+    <ol start="134" data-sourcepos="1:1-3:16" dir="auto">
+    <li data-sourcepos="1:1-1:16">list item 1</li>
+    <li data-sourcepos="2:1-2:16">list item 2</li>
+    <li data-sourcepos="3:1-3:16">list item 3</li>
+    </ol>
+
+- name: ordered_task_list
+  markdown: |-
+    1. [x] hello
+    2. [x] world
+    3. [ ] example
+       1. [ ] of nested
+          1. [x] task list
+          2. [ ] items
+  html: |-
+    <ol data-sourcepos="1:1-6:18" class="task-list" dir="auto">
+    <li data-sourcepos="1:1-1:12" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> hello</li>
+    <li data-sourcepos="2:1-2:12" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> world</li>
+    <li data-sourcepos="3:1-6:18" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" disabled> example
+    <ol data-sourcepos="4:4-6:18" class="task-list">
+    <li data-sourcepos="4:4-6:18" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" disabled> of nested
+    <ol data-sourcepos="5:7-6:18" class="task-list">
+    <li data-sourcepos="5:7-5:22" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> task list</li>
+    <li data-sourcepos="6:7-6:18" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" disabled> items</li>
+    </ol>
+    </li>
+    </ol>
+    </li>
+    </ol>
+
+- name: ordered_task_list_with_order
+  markdown: |-
+    4893. [x] hello
+    4894. [x] world
+    4895. [ ] example
+  html: |-
+    <ol start="4893" data-sourcepos="1:1-3:17" class="task-list" dir="auto">
+    <li data-sourcepos="1:1-1:15" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> hello</li>
+    <li data-sourcepos="2:1-2:15" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> world</li>
+    <li data-sourcepos="3:1-3:17" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" disabled> example</li>
+    </ol>
+
+- name: reference_for_project_wiki
+  api_context: project_wiki
+  substitutions:
+    # NOTE: We don't care about verifying specific attribute values here, that should be the
+    #       responsibility of unit tests. These tests are about the structure of the HTML.
+    uri_substitution: *uri_substitution
+    data_attribute_id_substitution:
+      - regex: '(data-user|data-project|data-issue|data-iid|data-merge-request|data-milestone)(=")(\d+?)(")'
+        replacement: '\1\2ID\4'
+    text_attribute_substitution:
+      - regex: '(title)(=")(.+?)(")'
+        replacement: '\1\2TEXT\4'
+    path_attribute_id_substitution:
+      - regex: '(group|project)(\d+)'
+        replacement: '\1ID'
+  markdown: |-
+    Hi @gfm_user - thank you for reporting this bug (#1) we hope to fix it in %1.1 as part of !1
+  html: |-
+    <p data-sourcepos="1:1-1:92" dir="auto">Hi <a href="/gfm_user" data-user="1" data-reference-type="user" data-container="body" data-placement="top" class="gfm gfm-project_member js-user-link" title="John Doe1">@gfm_user</a> - thank you for reporting this bug (<a href="/group1/project1/-/issues/1" data-original="#1" data-link="false" data-link-reference="false" data-project="11" data-issue="11" data-reference-type="issue" data-container="body" data-placement="top" title="My title 1" class="gfm gfm-issue has-tooltip">#1</a>) we hope to fix it in <a href="/group1/project1/-/milestones/1" data-original="%1.1" data-link="false" data-link-reference="false" data-project="11" data-milestone="11" data-reference-type="milestone" data-container="body" data-placement="top" title="" class="gfm gfm-milestone has-tooltip">%1.1</a> as part of <a href="/group1/project1/-/merge_requests/1" data-original="!1" data-link="false" data-link-reference="false" data-project="11" data-merge-request="11" data-project-path="group1/project1" data-iid="1" data-mr-title="My title 2" data-reference-type="merge_request" data-container="body" data-placement="top" title="" class="gfm gfm-merge_request">!1</a></p>
+- name: strike
+  markdown: |-
+    ~~del~~
+  html: |-
+    <p data-sourcepos="1:1-1:7" dir="auto"><del>del</del></p>
+
+- name: table
+  markdown: |-
+    | header | header |
+    |--------|--------|
+    | `code` | cell with **bold** |
+    | ~~strike~~ | cell with _italic_ |
+
+    # content after table
+  html: |-
+    <table data-sourcepos="1:1-4:35" dir="auto">
+    <thead>
+    <tr data-sourcepos="1:1-1:19">
+    <th data-sourcepos="1:2-1:9">header</th>
+    <th data-sourcepos="1:11-1:18">header</th>
+    </tr>
+    </thead>
+    <tbody>
+    <tr data-sourcepos="3:1-3:31">
+    <td data-sourcepos="3:2-3:9"><code>code</code></td>
+    <td data-sourcepos="3:11-3:30">cell with <strong>bold</strong>
+    </td>
+    </tr>
+    <tr data-sourcepos="4:1-4:35">
+    <td data-sourcepos="4:2-4:13"><del>strike</del></td>
+    <td data-sourcepos="4:15-4:34">cell with <em>italic</em>
+    </td>
+    </tr>
+    </tbody>
+    </table>
+    <h1 data-sourcepos="6:1-6:21" dir="auto">
+    <a id="user-content-content-after-table" class="anchor" href="#content-after-table" aria-hidden="true"></a>content after table</h1>
+
+- name: table_of_contents
+  markdown: |-
+    [[_TOC_]]
+
+    # Lorem
+
+    Well, that's just like... your opinion.. man.
+
+    ## Ipsum
+
+    ### Dolar
+
+    # Sit amit
+
+    ### I don't know
+  html: |-
+    <ul class="section-nav">
+    <li>
+    <a href="#lorem">Lorem</a><ul><li>
+    <a href="#ipsum">Ipsum</a><ul><li><a href="#dolar">Dolar</a></li></ul>
+    </li></ul>
+    </li>
+    <li>
+    <a href="#sit-amit">Sit amit</a><ul><li><a href="#i-dont-know">I don't know</a></li></ul>
+    </li>
+    </ul>
+    <h1 data-sourcepos="3:1-3:7" dir="auto">
+    <a id="user-content-lorem" class="anchor" href="#lorem" aria-hidden="true"></a>Lorem</h1>
+    <p data-sourcepos="5:1-5:45" dir="auto">Well, that's just like... your opinion.. man.</p>
+    <h2 data-sourcepos="7:1-7:8" dir="auto">
+    <a id="user-content-ipsum" class="anchor" href="#ipsum" aria-hidden="true"></a>Ipsum</h2>
+    <h3 data-sourcepos="9:1-9:9" dir="auto">
+    <a id="user-content-dolar" class="anchor" href="#dolar" aria-hidden="true"></a>Dolar</h3>
+    <h1 data-sourcepos="11:1-11:10" dir="auto">
+    <a id="user-content-sit-amit" class="anchor" href="#sit-amit" aria-hidden="true"></a>Sit amit</h1>
+    <h3 data-sourcepos="13:1-13:16" dir="auto">
+    <a id="user-content-i-dont-know" class="anchor" href="#i-dont-know" aria-hidden="true"></a>I don't know</h3>
+
+- name: task_list
+  markdown: |-
+    * [x] hello
+    * [x] world
+    * [ ] example
+      * [ ] of nested
+        * [x] task list
+        * [ ] items
+  html: |-
+    <ul data-sourcepos="1:1-6:15" class="task-list" dir="auto">
+    <li data-sourcepos="1:1-1:11" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> hello</li>
+    <li data-sourcepos="2:1-2:11" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> world</li>
+    <li data-sourcepos="3:1-6:15" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" disabled> example
+    <ul data-sourcepos="4:3-6:15" class="task-list">
+    <li data-sourcepos="4:3-6:15" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" disabled> of nested
+    <ul data-sourcepos="5:5-6:15" class="task-list">
+    <li data-sourcepos="5:5-5:19" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" checked disabled> task list</li>
+    <li data-sourcepos="6:5-6:15" class="task-list-item">
+    <input type="checkbox" class="task-list-item-checkbox" disabled> items</li>
+    </ul>
+    </li>
+    </ul>
+    </li>
+    </ul>
+
+- name: video
+  markdown: |-
+    ![Sample Video](https://gitlab.com/gitlab.mp4)
+  html: |-
+    <p data-sourcepos="1:1-1:46" dir="auto"><span class="media-container video-container"><video src="https://gitlab.com/gitlab.mp4" controls="true" data-setup="{}" data-title="Sample Video" width="400" preload="metadata"></video><a href="https://gitlab.com/gitlab.mp4" target="_blank" rel="nofollow noreferrer noopener" title="Download 'Sample Video'">Sample Video</a></span></p>
+
+- name: word_break
+  markdown: Fernstraßen<wbr>bau<wbr>privat<wbr>finanzierungs<wbr>gesetz
+  html: <p data-sourcepos="1:1-1:60" dir="auto">Fernstraßen<wbr>bau<wbr>privat<wbr>finanzierungs<wbr>gesetz</wbr></wbr></wbr></wbr></p>

spec/frontend/content_editor/markdown_processing_examples.js

-import fs from 'fs';
-import path from 'path';
-import jsYaml from 'js-yaml';
-// eslint-disable-next-line import/no-deprecated
-import { getJSONFixture } from 'helpers/fixtures';
-
-export const loadMarkdownApiResult = (testName) => {
-  const fixturePathPrefix = `api/markdown/${testName}.json`;
-
-  // eslint-disable-next-line import/no-deprecated
-  const fixture = getJSONFixture(fixturePathPrefix);
-  return fixture.body || fixture.html;
-};
-
-export const loadMarkdownApiExamples = () => {
-  const apiMarkdownYamlPath = path.join(__dirname, '..', 'fixtures', 'api_markdown.yml');
-  const apiMarkdownYamlText = fs.readFileSync(apiMarkdownYamlPath);
-  const apiMarkdownExampleObjects = jsYaml.safeLoad(apiMarkdownYamlText);
-
-  return apiMarkdownExampleObjects.map(({ name, context, markdown }) => [name, context, markdown]);
-};
-
-export const loadMarkdownApiExample = (testName) => {
-  return loadMarkdownApiExamples().find(([name, context]) => {
-    return (context ? `${context}_${name}` : name) === testName;
-  })[2];
-};

spec/frontend/content_editor/markdown_processing_spec.js

-import { createContentEditor } from '~/content_editor';
-import { loadMarkdownApiExamples, loadMarkdownApiResult } from './markdown_processing_examples';
+import path from 'path';
+import { createSharedExamples, loadMarkdownApiExamples } from './markdown_processing_spec_helper';
 
 jest.mock('~/emoji');
 
-describe('markdown processing', () => {
+// See spec/fixtures/markdown/markdown_golden_master_examples.yml for documentation on how this spec works.
+describe('markdown processing in ContentEditor', () => {
   // Ensure we generate same markdown that was provided to Markdown API.
-  it.each(loadMarkdownApiExamples())(
-    'correctly handles %s (context: %s)',
-    async (name, context, markdown) => {
-      const testName = context ? `${context}_${name}` : name;
-      const contentEditor = createContentEditor({
-        renderMarkdown: () => loadMarkdownApiResult(testName),
-      });
-      await contentEditor.setSerializedContent(markdown);
-
-      expect(contentEditor.getSerializedContent()).toBe(markdown);
-    },
+  const markdownYamlPath = path.join(
+    __dirname,
+    '..',
+    '..',
+    'fixtures',
+    'markdown',
+    'markdown_golden_master_examples.yml',
   );
+  // eslint-disable-next-line jest/valid-describe
+  describe.each(loadMarkdownApiExamples(markdownYamlPath))('%s', createSharedExamples);
 });

spec/frontend/content_editor/markdown_processing_spec_helper.js

+import fs from 'fs';
+import jsYaml from 'js-yaml';
+import { memoize } from 'lodash';
+import { createContentEditor } from '~/content_editor';
+import { setTestTimeoutOnce } from 'helpers/timeout';
+
+const getFocusedMarkdownExamples = memoize(
+  () => process.env.FOCUSED_MARKDOWN_EXAMPLES?.split(',') || [],
+);
+
+const includeExample = ({ name }) => {
+  const focusedMarkdownExamples = getFocusedMarkdownExamples();
+  if (!focusedMarkdownExamples.length) {
+    return true;
+  }
+  return focusedMarkdownExamples.includes(name);
+};
+
+const getPendingReason = (pendingStringOrObject) => {
+  if (!pendingStringOrObject) {
+    return null;
+  }
+  if (typeof pendingStringOrObject === 'string') {
+    return pendingStringOrObject;
+  }
+  if (pendingStringOrObject.frontend) {
+    return pendingStringOrObject.frontend;
+  }
+
+  return null;
+};
+
+// eslint-disable-next-line jest/no-export
+export const loadMarkdownApiExamples = (markdownYamlPath) => {
+  const apiMarkdownYamlText = fs.readFileSync(markdownYamlPath);
+  const apiMarkdownExampleObjects = jsYaml.safeLoad(apiMarkdownYamlText);
+
+  return apiMarkdownExampleObjects
+    .filter(includeExample)
+    .map(({ name, pending, markdown, html }) => [
+      name,
+      { pendingReason: getPendingReason(pending), markdown, html },
+    ]);
+};
+
+const testSerializesHtmlToMarkdownForElement = async ({ markdown, html }) => {
+  const contentEditor = createContentEditor({
+    // Overwrite renderMarkdown to always return this specific html
+    renderMarkdown: () => html,
+  });
+
+  await contentEditor.setSerializedContent(markdown);
+
+  // This serializes the ContentEditor document, which was based on the HTML, to markdown
+  const serializedContent = contentEditor.getSerializedContent();
+
+  // Assert that the markdown we ended up with after sending it through all the ContentEditor
+  // plumbing matches the original markdown from the YAML.
+  expect(serializedContent).toBe(markdown);
+};
+
+// eslint-disable-next-line jest/no-export
+export const createSharedExamples = (name, { pendingReason, ...example }) => {
+  const exampleName = 'correctly serializes HTML to markdown';
+  if (pendingReason) {
+    it.todo(`${exampleName}: ${pendingReason}`);
+  } else {
+    it(exampleName, async () => {
+      if (name === 'frontmatter_toml') {
+        setTestTimeoutOnce(2000);
+      }
+      await testSerializesHtmlToMarkdownForElement(example);
+    });
+  }
+};

spec/frontend/fixtures/api_markdown.rb

-# frozen_string_literal: true
-
-require 'spec_helper'
-
-RSpec.describe API::MergeRequests, '(JavaScript fixtures)', type: :request do
-  include ApiHelpers
-  include WikiHelpers
-  include JavaScriptFixturesHelpers
-
-  let_it_be(:user) { create(:user, username: 'gitlab') }
-
-  let_it_be(:group) { create(:group, :public) }
-  let_it_be(:project) { create(:project, :public, :repository, group: group) }
-
-  let_it_be(:label) { create(:label, project: project, title: 'bug') }
-  let_it_be(:milestone) { create(:milestone, project: project, title: '1.1') }
-  let_it_be(:issue) { create(:issue, project: project) }
-  let_it_be(:merge_request) { create(:merge_request, source_project: project) }
-
-  let_it_be(:project_wiki) { create(:project_wiki, project: project, user: user) }
-
-  let(:project_wiki_page) { create(:wiki_page, wiki: project_wiki) }
-
-  before(:all) do
-    group.add_owner(user)
-    project.add_maintainer(user)
-  end
-
-  before do
-    sign_in(user)
-  end
-
-  markdown_examples = begin
-    yaml_file_path = File.expand_path('api_markdown.yml', __dir__)
-    yaml = File.read(yaml_file_path)
-    YAML.safe_load(yaml, symbolize_names: true)
-  end
-
-  markdown_examples.each do |markdown_example|
-    context = markdown_example.fetch(:context, '')
-    name = markdown_example.fetch(:name)
-
-    context "for #{name}#{!context.empty? ? " (context: #{context})" : ''}" do
-      let(:markdown) { markdown_example.fetch(:markdown) }
-
-      name = "#{context}_#{name}" unless context.empty?
-
-      it "api/markdown/#{name}.json" do
-        api_url = case context
-                  when 'project'
-                    "/#{project.full_path}/preview_markdown"
-                  when 'group'
-                    "/groups/#{group.full_path}/preview_markdown"
-                  when 'project_wiki'
-                    "/#{project.full_path}/-/wikis/#{project_wiki_page.slug}/preview_markdown"
-                  else
-                    api "/markdown"
-                  end
-
-        post api_url, params: { text: markdown, gfm: true }
-        expect(response).to be_successful
-      end
-    end
-  end
-end

spec/frontend/fixtures/api_markdown.yml

-# This data file drives the specs in
-# spec/frontend/fixtures/api_markdown.rb and
-# spec/frontend/content_editor/extensions/markdown_processing_spec.js
----
-- name: attachment_image
-  context: group
-  markdown: '![test-file](/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png)'
-- name: attachment_image
-  context: project
-  markdown: '![test-file](/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.png)'
-- name: attachment_image
-  context: project_wiki
-  markdown: '![test-file](test-file.png)'
-- name: attachment_link
-  context: group
-  markdown: '[test-file](/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.zip)'
-- name: attachment_link
-  context: project
-  markdown: '[test-file](/uploads/aa45a38ec2cfe97433281b10bbff042c/test-file.zip)'
-- name: attachment_link
-  context: project_wiki
-  markdown: '[test-file](test-file.zip)'
-- name: audio
-  markdown: '![Sample Audio](https://gitlab.com/gitlab.mp3)'
-- name: audio_and_video_in_lists
-  markdown: |-
-    * ![Sample Audio](https://gitlab.com/1.mp3)
-    * ![Sample Video](https://gitlab.com/2.mp4)
-
-    1. ![Sample Video](https://gitlab.com/1.mp4)
-    2. ![Sample Audio](https://gitlab.com/2.mp3)
-
-    * [x] ![Sample Audio](https://gitlab.com/1.mp3)
-    * [x] ![Sample Audio](https://gitlab.com/2.mp3)
-    * [x] ![Sample Video](https://gitlab.com/3.mp4)
-- name: blockquote
-  markdown: |-
-    > This is a blockquote
-    >
-    > This is another one
-- name: bold
-  markdown: '**bold**'
-- name: bullet_list_style_1
-  markdown: |-
-    * list item 1
-    * list item 2
-      * embedded list item 3
-- name: bullet_list_style_2
-  markdown: |-
-    - list item 1
-    - list item 2
-      * embedded list item 3
-- name: bullet_list_style_3
-  markdown: |-
-    + list item 1
-    + list item 2
-      - embedded list item 3
-- name: code_block
-  markdown: |-
-    ```javascript
-      console.log('hello world')
-    ```
-- name: color_chips
-  markdown: |-
-    - `#F00`
-    - `#F00A`
-    - `#FF0000`
-    - `#FF0000AA`
-    - `RGB(0,255,0)`
-    - `RGB(0%,100%,0%)`
-    - `RGBA(0,255,0,0.3)`
-    - `HSL(540,70%,50%)`
-    - `HSLA(540,70%,50%,0.3)`
-- name: description_list
-  markdown: |-
-    <dl>
-    <dt>Frog</dt>
-    <dd>Wet green thing</dd>
-    <dt>Rabbit</dt>
-    <dd>Warm fluffy thing</dd>
-    <dt>Punt</dt>
-    <dd>Kick a ball</dd>
-    <dd>Take a bet</dd>
-    <dt>Color</dt>
-    <dt>Colour</dt>
-    <dd>
-
-    Any hue except _white_ or **black**
-
-    </dd>
-    </dl>
-- name: details
-  markdown: |-
-    <details>
-    <summary>Apply this patch</summary>
-
-    ```diff
-    diff --git a/spec/frontend/fixtures/api_markdown.yml b/spec/frontend/fixtures/api_markdown.yml
-    index 8433efaf00c..69b12c59d46 100644
-    --- a/spec/frontend/fixtures/api_markdown.yml
-    +++ b/spec/frontend/fixtures/api_markdown.yml
-    @@ -33,6 +33,13 @@
-         * <ruby>漢<rt>ㄏㄢˋ</rt></ruby>
-         * C<sub>7</sub>H<sub>16</sub> + O<sub>2</sub> → CO<sub>2</sub> + H<sub>2</sub>O
-         * The **Pythagorean theorem** is often expressed as <var>a<sup>2</sup></var> + <var>b<sup>2</sup></var> =  <var>c<sup>2</sup></var>.The **Pythagorean theorem** is often expressed as <var>a<sup>2</sup></var> + <var>b<sup>2</sup></var> = <var>c<sup>2</sup></var>
-    +- name: details
-    +  markdown: |-
-    +    <details>
-    +    <summary>Apply this patch</summary>
-    +
-    +    🐶 much meta, 🐶 many patch
-    +    🐶 such diff, 🐶 very meme
-    +    🐶 wow!
-    +    </details>
-     - name: link
-       markdown: '[GitLab](https://gitlab.com)'
-     - name: attachment_link
-    ```
-
-    </details>
-- name: div
-  markdown: |-
-    <div>plain text</div>
-    <div>
-
-    just a plain ol' div, not much to _expect_!
-
-    </div>
-- name: emoji
-  markdown: ':sparkles: :heart: :100:'
-- name: emphasis
-  markdown: '_emphasized text_'
-- name: figure
-  markdown: |-
-    <figure>
-
-    ![Elephant at sunset](elephant-sunset.jpg)
-
-    <figcaption>An elephant at sunset</figcaption>
-    </figure>
-    <figure>
-
-    ![A crocodile wearing crocs](croc-crocs.jpg)
-
-    <figcaption>
-
-    A crocodile wearing _crocs_!
-
-    </figcaption>
-    </figure>
-- name: frontmatter_json
-  markdown: |-
-    ;;;
-    {
-      "title": "Page title"
-    }
-    ;;;
-- name: frontmatter_toml
-  markdown: |-
-    +++
-    title = "Page title"
-    +++
-- name: frontmatter_yaml
-  markdown: |-
-    ---
-    title: Page title
-    ---
-- name: hard_break
-  markdown: |-
-    This is a line after a\
-    hard break
-- name: headings
-  markdown: |-
-    # Heading 1
-
-    ## Heading 2
-
-    ### Heading 3
-
-    #### Heading 4
-
-    ##### Heading 5
-
-    ###### Heading 6
-- name: horizontal_rule
-  markdown: '---'
-- name: html_marks
-  markdown: |-
-    * Content editor is ~~great~~<ins>amazing</ins>.
-    * If the changes <abbr title="Looks good to merge">LGTM</abbr>, please <abbr title="Merge when pipeline succeeds">MWPS</abbr>.
-    * The English song <q>Oh I do like to be beside the seaside</q> looks like this in Hebrew: <span dir="rtl">אה, אני אוהב להיות ליד חוף הים</span>. In the computer's memory, this is stored as <bdo dir="ltr">אה, אני אוהב להיות ליד חוף הים</bdo>.
-    * <cite>The Scream</cite> by Edvard Munch. Painted in 1893.
-    * <dfn>HTML</dfn> is the standard markup language for creating web pages.
-    * Do not forget to buy <mark>milk</mark> today.
-    * This is a paragraph and <small>smaller text goes here</small>.
-    * The concert starts at <time datetime="20:00">20:00</time> and you'll be able to enjoy the band for at least <time datetime="PT2H30M">2h 30m</time>.
-    * Press <kbd>Ctrl</kbd> + <kbd>C</kbd> to copy text (Windows).
-    * WWF's goal is to: <q>Build a future where people live in harmony with nature.</q> We hope they succeed.
-    * The error occured was: <samp>Keyboard not found. Press F1 to continue.</samp>
-    * The area of a triangle is: 1/2 x <var>b</var> x <var>h</var>, where <var>b</var> is the base, and <var>h</var> is the vertical height.
-    * <ruby>漢<rt>ㄏㄢˋ</rt></ruby>
-    * C<sub>7</sub>H<sub>16</sub> + O<sub>2</sub> → CO<sub>2</sub> + H<sub>2</sub>O
-    * The **Pythagorean theorem** is often expressed as <var>a<sup>2</sup></var> + <var>b<sup>2</sup></var> = <var>c<sup>2</sup></var>
-- name: image
-  markdown: '![alt text](https://gitlab.com/logo.png)'
-- name: inline_code
-  markdown: '`code`'
-- name: inline_diff
-  markdown: |-
-    * {-deleted-}
-    * {+added+}
-- name: link
-  markdown: '[GitLab](https://gitlab.com)'
-- name: math
-  markdown: |-
-    This math is inline $`a^2+b^2=c^2`$.
-
-    This is on a separate line:
-
-    ```math
-    a^2+b^2=c^2
-    ```
-- name: ordered_list
-  markdown: |-
-    1. list item 1
-    2. list item 2
-    3. list item 3
-- name: ordered_list_with_start_order
-  markdown: |-
-    134. list item 1
-    135. list item 2
-    136. list item 3
-- name: ordered_task_list
-  markdown: |-
-    1. [x] hello
-    2. [x] world
-    3. [ ] example
-       1. [ ] of nested
-          1. [x] task list
-          2. [ ] items
-- name: ordered_task_list_with_order
-  markdown: |-
-    4893. [x] hello
-    4894. [x] world
-    4895. [ ] example
-- name: reference
-  context: project_wiki
-  markdown: |-
-    Hi @gitlab - thank you for reporting this ~bug (#1) we hope to fix it in %1.1 as part of !1
-- name: strike
-  markdown: '~~del~~'
-- name: table
-  markdown: |-
-    | header | header |
-    |--------|--------|
-    | `code` | cell with **bold** |
-    | ~~strike~~ | cell with _italic_ |
-
-    # content after table
-- name: table_of_contents
-  markdown: |-
-    [[_TOC_]]
-
-    # Lorem
-
-    Well, that's just like... your opinion.. man.
-
-    ## Ipsum
-
-    ### Dolar
-
-    # Sit amit
-
-    ### I don't know
-- name: task_list
-  markdown: |-
-    * [x] hello
-    * [x] world
-    * [ ] example
-      * [ ] of nested
-        * [x] task list
-        * [ ] items
-- name: thematic_break
-  markdown: |-
-    ---
-- name: video
-  markdown: '![Sample Video](https://gitlab.com/gitlab.mp4)'
-- name: word_break
-  markdown: Fernstraßen<wbr>bau<wbr>privat<wbr>finanzierungs<wbr>gesetz

spec/requests/api/markdown_golden_master_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+# See spec/fixtures/markdown/markdown_golden_master_examples.yml for documentation on how this spec works.
+RSpec.describe API::Markdown, 'Golden Master' do
+  markdown_yml_file_path = File.expand_path('../../fixtures/markdown/markdown_golden_master_examples.yml', __dir__)
+  include_context 'API::Markdown Golden Master shared context', markdown_yml_file_path
+end

spec/spec_helper.rb

@@ -454,6 +454,13 @@ RSpec.configure do |config|
     $stdout = StringIO.new
   end
 
+  # Makes diffs show entire non-truncated values.
+  config.before(:each, unlimited_max_formatted_output_length: true) do |_example|
+    config.expect_with :rspec do |c|
+      c.max_formatted_output_length = nil
+    end
+  end
+
   config.after(:each, :silence_stdout) do
     $stdout = STDOUT
   end

spec/support/shared_contexts/markdown_golden_master_shared_examples.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+# See spec/fixtures/markdown/markdown_golden_master_examples.yml for documentation on how this spec works.
+RSpec.shared_context 'API::Markdown Golden Master shared context' do |markdown_yml_file_path|
+  include ApiHelpers
+  include WikiHelpers
+
+  let_it_be(:user) { create(:user, username: 'gfm_user') }
+
+  let_it_be(:group) { create(:group, :public) }
+  let_it_be(:project) { create(:project, :public, :repository, group: group) }
+
+  let_it_be(:label) { create(:label, project: project, title: 'bug') }
+  let_it_be(:milestone) { create(:milestone, project: project, title: '1.1') }
+  let_it_be(:issue) { create(:issue, project: project) }
+  let_it_be(:merge_request) { create(:merge_request, source_project: project) }
+
+  let_it_be(:project_wiki) { create(:project_wiki, project: project, user: user) }
+
+  let_it_be(:project_wiki_page) { create(:wiki_page, wiki: project_wiki) }
+
+  before(:all) do
+    group.add_owner(user)
+    project.add_maintainer(user)
+  end
+
+  before do
+    sign_in(user)
+  end
+
+  markdown_examples = begin
+    yaml = File.read(markdown_yml_file_path)
+    YAML.safe_load(yaml, symbolize_names: true, aliases: true)
+  end
+
+  it "examples must be unique and alphabetized by name", :unlimited_max_formatted_output_length do
+    names = markdown_examples.map { |example| example[:name] }
+    expect(names).to eq(names.sort.uniq)
+  end
+
+  if focused_markdown_examples_string = ENV['FOCUSED_MARKDOWN_EXAMPLES']
+    focused_markdown_examples = focused_markdown_examples_string.split(',').map(&:strip) || []
+    markdown_examples.reject! {|markdown_example| !focused_markdown_examples.include?(markdown_example.fetch(:name)) }
+  end
+
+  markdown_examples.each do |markdown_example|
+    name = markdown_example.fetch(:name)
+    api_context = markdown_example[:api_context]
+
+    if api_context && !name.end_with?("_for_#{api_context}")
+      raise "Name must have suffix of '_for_#{api_context}' to the api_context"
+    end
+
+    context "for #{name}#{api_context ? " (api_context: #{api_context})" : ''}" do
+      let(:pending_reason) do
+        pending_value = markdown_example.fetch(:pending, nil)
+        get_pending_reason(pending_value)
+      end
+
+      let(:example_markdown) { markdown_example.fetch(:markdown) }
+      let(:example_html) { markdown_example.fetch(:html) }
+      let(:substitutions) { markdown_example.fetch(:substitutions, {}) }
+
+      it "verifies conversion of GFM to HTML", :unlimited_max_formatted_output_length do
+        pending pending_reason if pending_reason
+
+        normalized_example_html = normalize_html(example_html, substitutions)
+
+        api_url = get_url_for_api_context(api_context)
+
+        post api_url, params: { text: example_markdown, gfm: true }
+        expect(response).to be_successful
+        response_body = Gitlab::Json.parse(response.body)
+        # Some requests have the HTML in the `html` key, others in the `body` key.
+        response_html = response_body['body'] ? response_body.fetch('body') : response_body.fetch('html')
+        normalized_response_html = normalize_html(response_html, substitutions)
+
+        expect(normalized_response_html).to eq(normalized_example_html)
+      end
+
+      def get_pending_reason(pending_value)
+        return false unless pending_value
+
+        return pending_value if pending_value.is_a?(String)
+
+        pending_value[:backend] || false
+      end
+
+      def normalize_html(html, substitutions)
+        normalized_html = html.dup
+        # Note: having the top level `substitutions` data structure be a hash of arrays
+        # allows us to compose multiple substitutions via YAML anchors (YAML anchors
+        # pointing to arrays can't be combined)
+        substitutions.each_value do |substitution_entry|
+          substitution_entry.each do |substitution|
+            regex = substitution.fetch(:regex)
+            replacement = substitution.fetch(:replacement)
+            normalized_html.gsub!(%r{#{regex}}, replacement)
+          end
+        end
+
+        normalized_html
+      end
+    end
+  end
+
+  def supported_api_contexts
+    %w(project group project_wiki)
+  end
+
+  def get_url_for_api_context(api_context)
+    case api_context
+    when 'project'
+      "/#{project.full_path}/preview_markdown"
+    when 'group'
+      "/groups/#{group.full_path}/preview_markdown"
+    when 'project_wiki'
+      "/#{project.full_path}/-/wikis/#{project_wiki_page.slug}/preview_markdown"
+    when nil
+      api "/markdown"
+    else
+      raise "Error: 'context' extension was '#{api_context}'. It must be one of: #{supported_api_contexts.join(',')}"
+    end
+  end
+end