diff --git a/Gemfile b/Gemfile
index e18f5638..8b54d56d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -27,9 +27,10 @@ group :development do
 end
 
 group :test do
-  gem "commonmarker", "~> 1.0.0.pre4", require: false
+  gem "commonmarker", "~> 1.0.0.pre7", require: false
   gem "gemoji", "~> 3.0", require: false
   gem "gemojione", "~> 4.3", require: false
+
   gem "minitest"
 
   gem "minitest-bisect", "~> 1.6"
@@ -37,4 +38,5 @@ group :test do
   gem "nokogiri", "~> 1.13"
 
   gem "minitest-focus", "~> 1.1"
+  gem "rouge", "~> 3.1", require: false
 end
diff --git a/README.md b/README.md
index c3231e7d..1eb52fc9 100644
--- a/README.md
+++ b/README.md
@@ -230,19 +230,28 @@ end
 
 For more information on how to write effective `NodeFilter`s, refer to the provided filters, and see the underlying lib, [Selma](https://www.github.com/gjtorikian/selma) for more information.
 
-- `AbsoluteSourceFilter` - replace relative image urls with fully qualified versions
-- `EmojiFilter` - converts `:<emoji>:` to [emoji](http://www.emoji-cheat-sheet.com/)!
-- `HttpsFilter` - Replacing http urls with https versions
-- `ImageMaxWidthFilter` - link to full size image for large images
-- `MentionFilter` - replace `@user` mentions with links
-- `SanitizationFilter` - allow sanitize user markup
-- `TableOfContentsFilter` - anchor headings with name attributes and generate Table of Contents html unordered list linking headings
-- `TeamMentionFilter` - replace `@org/team` mentions with links
+- `AbsoluteSourceFilter`: replace relative image urls with fully qualified versions
+- `EmojiFilter`: converts `:<emoji>:` to [emoji](http://www.emoji-cheat-sheet.com/)
+  - (Note: the included `MarkdownFilter` will already convert emoji)
+- `HttpsFilter`: Replacing http urls with https versions
+- `ImageMaxWidthFilter`: link to full size image for large images
+- `MentionFilter`: replace `@user` mentions with links
+- `SanitizationFilter`: allow sanitize user markup
+- `SyntaxHighlightFilter`: applies syntax highlighting to `pre` blocks
+  - (Note: the included `MarkdownFilter` will already apply highlighting)
+- `TableOfContentsFilter`: anchor headings with name attributes and generate Table of Contents html unordered list linking headings
+- `TeamMentionFilter`: replace `@org/team` mentions with links
 
 ## Dependencies
 
-Since filters can be customized to your heart's content, gem dependencies are _not_ bundled; this project doesn't know which of the default filters you might use, and as such, you must bundle each filter's gem
-dependencies yourself.
+Since filters can be customized to your heart's content, gem dependencies are _not_ bundled; this project doesn't know which of the default filters you might use, and as such, you must bundle each filter's gem dependencies yourself.
+
+For example, `SyntaxHighlightFilter` uses [rouge](https://github.com/jneen/rouge)
+to detect and highlight languages; to use the `SyntaxHighlightFilter`, you must add the following to your Gemfile:
+
+```ruby
+gem "rouge"
+```
 
 > **Note**
 > See the [Gemfile](/Gemfile) `:test` group for any version requirements.
diff --git a/UPGRADING.md b/UPGRADING.md
index f0565678..3bd7e5a0 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -13,7 +13,6 @@ This project is now under a module called `HTMLPipeline`, not `HTML::Pipeline`.
 The following filters were removed:
 
 - `AutolinkFilter`: this is handled by [Commonmarker](https://www.github.com/gjtorikian/commonmarker) and can be disabled/enabled through the `MarkdownFilter`'s `context` hash
-- `SyntaxHighlightFilter`: this is handled by [Commonmarker](https://www.github.com/gjtorikian/commonmarker) and can be disabled/enabled through the `MarkdownFilter`'s `context` hash
 - `SanitizationFilter`: this is handled by [Selma](https://www.github.com/gjtorikian/selma); configuration can be done through the `sanitization_config` hash
 
 - `EmailReplyFilter`
diff --git a/lib/html_pipeline.rb b/lib/html_pipeline.rb
index ad709561..4e542814 100644
--- a/lib/html_pipeline.rb
+++ b/lib/html_pipeline.rb
@@ -145,8 +145,11 @@ def call(text, context: {}, result: {})
     context = context.freeze
     result ||= {}
 
-    payload = default_payload({ text_filters: @text_filters.map(&:name),
-                                context: context, result: result, })
+    payload = default_payload({
+      text_filters: @text_filters.map(&:name),
+      context: context,
+      result: result,
+    })
     instrument("call_text_filters.html_pipeline", payload) do
       result[:output] =
         @text_filters.inject(text) do |doc, filter|
@@ -159,8 +162,11 @@ def call(text, context: {}, result: {})
     html = @convert_filter.call(text) unless @convert_filter.nil?
 
     unless @node_filters.empty?
-      payload = default_payload({ node_filters: @node_filters.map { |f| f.class.name },
-        context: context, result: result, })
+      payload = default_payload({
+        node_filters: @node_filters.map { |f| f.class.name },
+        context: context,
+        result: result,
+      })
       instrument("call_node_filters.html_pipeline", payload) do
         result[:output] = Selma::Rewriter.new(sanitizer: @sanitization_config, handlers: @node_filters).rewrite(html)
       end
@@ -178,8 +184,11 @@ def call(text, context: {}, result: {})
   #
   # Returns the result of the filter.
   def perform_filter(filter, doc, context: {}, result: {})
-    payload = default_payload({ filter: filter.name,
-                                context: context, result: result, })
+    payload = default_payload({
+      filter: filter.name,
+      context: context,
+      result: result,
+    })
     instrument("call_filter.html_pipeline", payload) do
       filter.call(doc, context: context, result: result)
     end
diff --git a/lib/html_pipeline/node_filter/syntax_highlight_filter.rb b/lib/html_pipeline/node_filter/syntax_highlight_filter.rb
new file mode 100644
index 00000000..2fcda21b
--- /dev/null
+++ b/lib/html_pipeline/node_filter/syntax_highlight_filter.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+HTMLPipeline.require_dependency("rouge", "SyntaxHighlightFilter")
+
+class HTMLPipeline
+  class NodeFilter
+    # HTML Filter that syntax highlights text inside code blocks.
+    #
+    # Context options:
+    #
+    #   :highlight => String represents the language to pick lexer. Defaults to empty string.
+    #   :scope => String represents the class attribute adds to pre element after.
+    #             Defaults to "highlight highlight-css" if highlights a css code block.
+    #
+    # This filter does not write any additional information to the context hash.
+    class SyntaxHighlightFilter < NodeFilter
+      def initialize(context: {}, result: {})
+        super(context: context, result: result)
+        # TODO: test the optionality of this
+        @formatter = context[:formatter] || Rouge::Formatters::HTML.new
+      end
+
+      SELECTOR = Selma::Selector.new(match_element: "pre", match_text_within: "pre")
+
+      def selector
+        SELECTOR
+      end
+
+      def handle_element(element)
+        default = context[:highlight]&.to_s
+        @lang = element["lang"] || default
+
+        scope = context.fetch(:scope, "highlight")
+
+        element["class"] = "#{scope} #{scope}-#{@lang}" if include_lang?
+      end
+
+      def handle_text_chunk(text)
+        return if @lang.nil?
+        return if (lexer = lexer_for(@lang)).nil?
+
+        content = text.to_s
+
+        text.replace(highlight_with_timeout_handling(content, lexer), as: :html)
+      end
+
+      def highlight_with_timeout_handling(text, lexer)
+        Rouge.highlight(text, lexer, @formatter)
+      rescue Timeout::Error => _e
+        text
+      end
+
+      def lexer_for(lang)
+        Rouge::Lexer.find(lang)
+      end
+
+      def include_lang?
+        !@lang.nil? && !@lang.empty?
+      end
+    end
+  end
+end
diff --git a/lib/html_pipeline/node_filter/table_of_contents_filter.rb b/lib/html_pipeline/node_filter/table_of_contents_filter.rb
index 3017a8ea..6b8d8545 100644
--- a/lib/html_pipeline/node_filter/table_of_contents_filter.rb
+++ b/lib/html_pipeline/node_filter/table_of_contents_filter.rb
@@ -24,8 +24,10 @@ class NodeFilter
     #  result[:output].to_s
     #  # => "<h1>\n<a id=\"ice-cube\" class=\"anchor\" href=\"#ice-cube\">..."
     class TableOfContentsFilter < NodeFilter
-      SELECTOR = Selma::Selector.new(match_element: "h1 a[href], h2 a[href], h3 a[href], h4 a[href], h5 a[href], h6 a[href]",
-        match_text_within: "h1, h2, h3, h4, h5, h6")
+      SELECTOR = Selma::Selector.new(
+        match_element: "h1 a[href], h2 a[href], h3 a[href], h4 a[href], h5 a[href], h6 a[href]",
+        match_text_within: "h1, h2, h3, h4, h5, h6",
+      )
 
       def selector
         SELECTOR
diff --git a/lib/html_pipeline/sanitization_filter.rb b/lib/html_pipeline/sanitization_filter.rb
index 002d8115..020c5487 100644
--- a/lib/html_pipeline/sanitization_filter.rb
+++ b/lib/html_pipeline/sanitization_filter.rb
@@ -16,11 +16,70 @@ class SanitizationFilter
     # The main sanitization allowlist. Only these elements and attributes are
     # allowed through by default.
     DEFAULT_CONFIG = Selma::Sanitizer::Config.freeze_config({
-      elements: ["h1", "h2", "h3", "h4", "h5", "h6", "br", "b", "i", "strong", "em", "a", "pre", "code",
-                 "img", "tt", "div", "ins", "del", "sup", "sub", "p", "picture", "ol", "ul", "table", "thead", "tbody", "tfoot",
-                 "blockquote", "dl", "dt", "dd", "kbd", "q", "samp", "var", "hr", "ruby", "rt", "rp", "li", "tr", "td", "th",
-                 "s", "strike", "summary", "details", "caption", "figure", "figcaption", "abbr", "bdo", "cite",
-                 "dfn", "mark", "small", "source", "span", "time", "wbr",],
+      elements: [
+        "h1",
+        "h2",
+        "h3",
+        "h4",
+        "h5",
+        "h6",
+        "br",
+        "b",
+        "i",
+        "strong",
+        "em",
+        "a",
+        "pre",
+        "code",
+        "img",
+        "tt",
+        "div",
+        "ins",
+        "del",
+        "sup",
+        "sub",
+        "p",
+        "picture",
+        "ol",
+        "ul",
+        "table",
+        "thead",
+        "tbody",
+        "tfoot",
+        "blockquote",
+        "dl",
+        "dt",
+        "dd",
+        "kbd",
+        "q",
+        "samp",
+        "var",
+        "hr",
+        "ruby",
+        "rt",
+        "rp",
+        "li",
+        "tr",
+        "td",
+        "th",
+        "s",
+        "strike",
+        "summary",
+        "details",
+        "caption",
+        "figure",
+        "figcaption",
+        "abbr",
+        "bdo",
+        "cite",
+        "dfn",
+        "mark",
+        "small",
+        "source",
+        "span",
+        "time",
+        "wbr",
+      ],
 
       attributes: {
         "a" => ["href"],
@@ -31,13 +90,77 @@ class SanitizationFilter
         "ins" => ["cite"],
         "q" => ["cite"],
         "source" => ["srcset"],
-        all: ["abbr", "accept", "accept-charset", "accesskey", "action", "align", "alt", "aria-describedby",
-              "aria-hidden", "aria-label", "aria-labelledby", "axis", "border", "char",
-              "charoff", "charset", "checked", "clear", "cols", "colspan", "compact", "coords", "datetime", "dir",
-              "disabled", "enctype", "for", "frame", "headers", "height", "hreflang", "hspace", "id", "ismap", "label", "lang",
-              "maxlength", "media", "method", "multiple", "name", "nohref", "noshade", "nowrap", "open", "progress",
-              "prompt", "readonly", "rel", "rev", "role", "rows", "rowspan", "rules", "scope", "selected", "shape",
-              "size", "span", "start", "summary", "tabindex",  "title", "type", "usemap", "valign", "value", "width", "itemprop",],
+        all: [
+          "abbr",
+          "accept",
+          "accept-charset",
+          "accesskey",
+          "action",
+          "align",
+          "alt",
+          "aria-describedby",
+          "aria-hidden",
+          "aria-label",
+          "aria-labelledby",
+          "axis",
+          "border",
+          "char",
+          "charoff",
+          "charset",
+          "checked",
+          "clear",
+          "cols",
+          "colspan",
+          "compact",
+          "coords",
+          "datetime",
+          "dir",
+          "disabled",
+          "enctype",
+          "for",
+          "frame",
+          "headers",
+          "height",
+          "hreflang",
+          "hspace",
+          "id",
+          "ismap",
+          "label",
+          "lang",
+          "maxlength",
+          "media",
+          "method",
+          "multiple",
+          "name",
+          "nohref",
+          "noshade",
+          "nowrap",
+          "open",
+          "progress",
+          "prompt",
+          "readonly",
+          "rel",
+          "rev",
+          "role",
+          "rows",
+          "rowspan",
+          "rules",
+          "scope",
+          "selected",
+          "shape",
+          "size",
+          "span",
+          "start",
+          "summary",
+          "tabindex",
+          "title",
+          "type",
+          "usemap",
+          "valign",
+          "value",
+          "width",
+          "itemprop",
+        ],
       },
       protocols: {
         "a" => { "href" => Selma::Sanitizer::Config::VALID_PROTOCOLS }.freeze,
diff --git a/lib/html_pipeline/version.rb b/lib/html_pipeline/version.rb
index fbe6f8a8..8d9b4e7e 100644
--- a/lib/html_pipeline/version.rb
+++ b/lib/html_pipeline/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 class HTMLPipeline
-  VERSION = "3.0.0.pre1"
+  VERSION = "3.0.0.pre2"
 end
diff --git a/test/html_pipeline/convert_filter/markdown_filter_test.rb b/test/html_pipeline/convert_filter/markdown_filter_test.rb
index e656e080..51827b85 100644
--- a/test/html_pipeline/convert_filter/markdown_filter_test.rb
+++ b/test/html_pipeline/convert_filter/markdown_filter_test.rb
@@ -62,78 +62,103 @@ def test_fenced_code_blocks_with_language
     def test_standard_extensions
       iframe = "<iframe src='http://www.google.com'></iframe>"
       iframe_escaped = "&lt;iframe src='http://www.google.com'>&lt;/iframe>"
-      doc = MarkdownFilter.call(iframe, context: { markdown: { render: { unsafe_: true } } })
+      doc = MarkdownFilter.call(iframe, context: { markdown: { render: { unsafe: true } } })
 
       assert_equal(doc, iframe_escaped)
     end
 
     def test_changing_extensions
       iframe = "<iframe src='http://www.google.com'></iframe>"
-      doc = MarkdownFilter.call(iframe, context: { markdown: { extension: { tagfilter: false }, render: { unsafe_: true } } })
+      doc = MarkdownFilter.call(iframe, context: { markdown: { extension: { tagfilter: false }, render: { unsafe: true } } })
 
       assert_equal(doc, iframe)
     end
 
     def test_without_tagfilter
-      options = { render: { unsafe_: true }, extension: { tagfilter: false } }
+      options = { render: { unsafe: true }, extension: { tagfilter: false } }
       script = "<script>foobar</script>"
       results = MarkdownFilter.call(script, context: { markdown: options })
 
       assert_equal(results, script)
     end
+
+    def test_renders_emoji
+      html = MarkdownFilter.call(":raccoon:")
+      result = "<p>🦝</p>"
+
+      assert_equal(result, html)
+    end
   end
 end
 
 class GFMTest < Minitest::Test
   def setup
     @gfm = MarkdownFilter
-    @context = { markdown: { render: { unsafe_: true }, plugins: { syntax_highlighter: nil } } }
+    @context = { markdown: { render: { unsafe: true }, plugins: { syntax_highlighter: nil } } }
   end
 
   def test_not_touch_single_underscores_inside_words
-    assert_equal("<p>foo_bar</p>",
-      @gfm.call("foo_bar", context: @context))
+    assert_equal(
+      "<p>foo_bar</p>",
+      @gfm.call("foo_bar", context: @context),
+    )
   end
 
   def test_not_touch_underscores_in_code_blocks
-    assert_equal("<pre><code>foo_bar_baz\n</code></pre>",
-      @gfm.call("    foo_bar_baz", context: @context))
+    assert_equal(
+      "<pre><code>foo_bar_baz\n</code></pre>",
+      @gfm.call("    foo_bar_baz", context: @context),
+    )
   end
 
   def test_not_touch_underscores_in_pre_blocks
-    assert_equal("<pre>\nfoo_bar_baz\n</pre>",
-      @gfm.call("<pre>\nfoo_bar_baz\n</pre>", context: @context))
+    assert_equal(
+      "<pre>\nfoo_bar_baz\n</pre>",
+      @gfm.call("<pre>\nfoo_bar_baz\n</pre>", context: @context),
+    )
   end
 
   def test_not_touch_two_or_more_underscores_inside_words
-    assert_equal("<p>foo_bar_baz</p>",
-      @gfm.call("foo_bar_baz", context: @context))
+    assert_equal(
+      "<p>foo_bar_baz</p>",
+      @gfm.call("foo_bar_baz", context: @context),
+    )
   end
 
   def test_turn_newlines_into_br_tags_in_simple_cases
-    assert_equal("<p>foo<br />\nbar</p>",
-      @gfm.call("foo  \nbar", context: @context))
+    assert_equal(
+      "<p>foo<br />\nbar</p>",
+      @gfm.call("foo  \nbar", context: @context),
+    )
   end
 
   def test_convert_newlines_in_all_groups
-    assert_equal("<p>apple<br />\npear<br />\norange</p>\n" \
-      "<p>ruby<br />\npython<br />\nerlang</p>",
-      @gfm.call("apple  \npear  \norange  \n\nruby  \npython  \nerlang", context: @context))
+    assert_equal(
+      "<p>apple<br />\npear<br />\norange</p>\n" \
+        "<p>ruby<br />\npython<br />\nerlang</p>",
+      @gfm.call("apple  \npear  \norange  \n\nruby  \npython  \nerlang", context: @context),
+    )
   end
 
   def test_convert_newlines_in_even_long_groups
-    assert_equal("<p>apple<br />\npear<br />\norange<br />\nbanana</p>\n" \
-      "<p>ruby<br />\npython<br />\nerlang</p>",
-      @gfm.call("apple  \npear  \norange  \nbanana  \n\nruby  \npython  \nerlang", context: @context))
+    assert_equal(
+      "<p>apple<br />\npear<br />\norange<br />\nbanana</p>\n" \
+        "<p>ruby<br />\npython<br />\nerlang</p>",
+      @gfm.call("apple  \npear  \norange  \nbanana  \n\nruby  \npython  \nerlang", context: @context),
+    )
   end
 
   def test_not_convert_newlines_in_lists
     options = Commonmarker::Config.merged_with_defaults({})
     options[:extension].delete(:header_ids)
 
-    assert_equal("<h1>foo</h1>\n<h1>bar</h1>",
-      @gfm.call("# foo\n# bar", context: { markdown: options }))
-    assert_equal("<ul>\n<li>foo</li>\n<li>bar</li>\n</ul>",
-      @gfm.call("* foo\n* bar", context: { markdown: options }))
+    assert_equal(
+      "<h1>foo</h1>\n<h1>bar</h1>",
+      @gfm.call("# foo\n# bar", context: { markdown: options }),
+    )
+    assert_equal(
+      "<ul>\n<li>foo</li>\n<li>bar</li>\n</ul>",
+      @gfm.call("* foo\n* bar", context: { markdown: options }),
+    )
   end
 end
diff --git a/test/html_pipeline/node_filter/absolute_source_filter_test.rb b/test/html_pipeline/node_filter/absolute_source_filter_test.rb
index 0cd36a10..b5d23aad 100644
--- a/test/html_pipeline/node_filter/absolute_source_filter_test.rb
+++ b/test/html_pipeline/node_filter/absolute_source_filter_test.rb
@@ -18,15 +18,19 @@ def setup
       def test_rewrites_root_urls
         orig = %(<p><img src="/img.png"></p>)
 
-        assert_equal("<p><img src=\"#{@image_base_url}/img.png\"></p>",
-          AbsoluteSourceFilter.call(orig, context: @options).to_s)
+        assert_equal(
+          "<p><img src=\"#{@image_base_url}/img.png\"></p>",
+          AbsoluteSourceFilter.call(orig, context: @options).to_s,
+        )
       end
 
       def test_rewrites_relative_urls
         orig = %(<p><img src="post/img.png"></p>)
 
-        assert_equal("<p><img src=\"#{@image_subpage_url}/img.png\"></p>",
-          AbsoluteSourceFilter.call(orig, context: @options).to_s)
+        assert_equal(
+          "<p><img src=\"#{@image_subpage_url}/img.png\"></p>",
+          AbsoluteSourceFilter.call(orig, context: @options).to_s,
+        )
       end
 
       def test_does_not_rewrite_absolute_urls
diff --git a/test/html_pipeline/node_filter/https_filter_test.rb b/test/html_pipeline/node_filter/https_filter_test.rb
index 98eb25b9..ef52f7b1 100644
--- a/test/html_pipeline/node_filter/https_filter_test.rb
+++ b/test/html_pipeline/node_filter/https_filter_test.rb
@@ -11,23 +11,31 @@ def setup
     end
 
     def test_http
-      assert_equal(%(<a href="https://github.com">github.com</a>),
-        HttpsFilter.call(%(<a href="http://github.com">github.com</a>), context: @options))
+      assert_equal(
+        %(<a href="https://github.com">github.com</a>),
+        HttpsFilter.call(%(<a href="http://github.com">github.com</a>), context: @options),
+      )
     end
 
     def test_https
-      assert_equal(%(<a href="https://github.com">github.com</a>),
-        HttpsFilter.call(%(<a href="https://github.com">github.com</a>), context: @options))
+      assert_equal(
+        %(<a href="https://github.com">github.com</a>),
+        HttpsFilter.call(%(<a href="https://github.com">github.com</a>), context: @options),
+      )
     end
 
     def test_subdomain
-      assert_equal(%(<a href="https://help.github.com">github.com</a>),
-        HttpsFilter.call(%(<a href="http://help.github.com">github.com</a>), context: @options))
+      assert_equal(
+        %(<a href="https://help.github.com">github.com</a>),
+        HttpsFilter.call(%(<a href="http://help.github.com">github.com</a>), context: @options),
+      )
     end
 
     def test_other
-      assert_equal(%(<a href="https://github.io">github.io</a>),
-        HttpsFilter.call(%(<a href="http://github.io">github.io</a>), context: @options))
+      assert_equal(
+        %(<a href="https://github.io">github.io</a>),
+        HttpsFilter.call(%(<a href="http://github.io">github.io</a>), context: @options),
+      )
     end
   end
 end
diff --git a/test/html_pipeline/node_filter/image_max_width_filter_test.rb b/test/html_pipeline/node_filter/image_max_width_filter_test.rb
index df7f4f9d..347bed50 100644
--- a/test/html_pipeline/node_filter/image_max_width_filter_test.rb
+++ b/test/html_pipeline/node_filter/image_max_width_filter_test.rb
@@ -12,8 +12,10 @@ def test_rewrites_image_style_tags
       body = '<p>Screenshot: <img src="screenshot.png"></p>'
       res = @filter.call(body)
 
-      assert_equal('<p>Screenshot: <a target="_blank" href="screenshot.png"><img src="screenshot.png" style="max-width:100%;"></a></p>',
-        res)
+      assert_equal(
+        '<p>Screenshot: <a target="_blank" href="screenshot.png"><img src="screenshot.png" style="max-width:100%;"></a></p>',
+        res,
+      )
     end
 
     def test_leaves_existing_image_style_tags_alone
@@ -21,8 +23,10 @@ def test_leaves_existing_image_style_tags_alone
 
       res = @filter.call(body)
 
-      assert_equal('<p><img src="screenshot.png" style="width:100px;"></p>',
-        res)
+      assert_equal(
+        '<p><img src="screenshot.png" style="width:100px;"></p>',
+        res,
+      )
     end
 
     def test_links_to_image
@@ -30,8 +34,10 @@ def test_links_to_image
 
       res = @filter.call(body)
 
-      assert_equal('<p>Screenshot: <a target="_blank" href="screenshot.png"><img src="screenshot.png" style="max-width:100%;"></a></p>',
-        res)
+      assert_equal(
+        '<p>Screenshot: <a target="_blank" href="screenshot.png"><img src="screenshot.png" style="max-width:100%;"></a></p>',
+        res,
+      )
     end
 
     def test_doesnt_link_to_image_when_already_linked
@@ -39,8 +45,10 @@ def test_doesnt_link_to_image_when_already_linked
 
       res = @filter.call(body)
 
-      assert_equal('<p>Screenshot: <a href="blah.png"><img src="screenshot.png" style="max-width:100%;"></a></p>',
-        res)
+      assert_equal(
+        '<p>Screenshot: <a href="blah.png"><img src="screenshot.png" style="max-width:100%;"></a></p>',
+        res,
+      )
     end
 
     def test_doesnt_screw_up_inlined_images
diff --git a/test/html_pipeline/node_filter/mention_filter_test.rb b/test/html_pipeline/node_filter/mention_filter_test.rb
index bcd9b2d1..7aee6b12 100644
--- a/test/html_pipeline/node_filter/mention_filter_test.rb
+++ b/test/html_pipeline/node_filter/mention_filter_test.rb
@@ -8,11 +8,13 @@ def setup
       @filter = HTMLPipeline::NodeFilter::MentionFilter
       @context = { base_url: "/", info_url: nil, username_pattern: nil }
 
-      @pipeline = HTMLPipeline.new(convert_filter:
-        HTMLPipeline::ConvertFilter::MarkdownFilter.new,
+      @pipeline = HTMLPipeline.new(
+        convert_filter:
+                HTMLPipeline::ConvertFilter::MarkdownFilter.new,
         node_filters: [
           HTMLPipeline::NodeFilter::MentionFilter.new,
-        ])
+        ],
+      )
     end
 
     def mentioned_usernames(body)
@@ -27,8 +29,10 @@ def test_filtering_plain_text
 
         link = '<a href="/kneath" class="user-mention">@kneath</a>'
 
-        assert_equal("<p>#{link}: check it out.</p>",
-          res)
+        assert_equal(
+          "<p>#{link}: check it out.</p>",
+          res,
+        )
       end
 
     def test_not_replacing_mentions_in_pre_tags
@@ -65,32 +69,40 @@ def test_html_injection
       body = "<p>@kneath &lt;script>alert(0)&lt;/script></p>"
       link = '<a href="/kneath" class="user-mention">@kneath</a>'
 
-      assert_equal("<p>#{link} &lt;script>alert(0)&lt;/script></p>",
-        @filter.call(body, context: @context))
+      assert_equal(
+        "<p>#{link} &lt;script>alert(0)&lt;/script></p>",
+        @filter.call(body, context: @context),
+      )
     end
 
     def test_base_url_slash
       body = "<p>Hi, @jch!</p>"
       link = '<a href="/jch" class="user-mention">@jch</a>'
 
-      assert_equal("<p>Hi, #{link}!</p>",
-        @filter.call(body, context: { base_url: "/" }))
+      assert_equal(
+        "<p>Hi, #{link}!</p>",
+        @filter.call(body, context: { base_url: "/" }),
+      )
     end
 
     def test_base_url_under_custom_route
       body = "<p>Hi, @jch!</p>"
       link = '<a href="/userprofile/jch" class="user-mention">@jch</a>'
 
-      assert_equal("<p>Hi, #{link}!</p>",
-        @filter.call(body, context: @context.merge({ base_url: "/userprofile" })))
+      assert_equal(
+        "<p>Hi, #{link}!</p>",
+        @filter.call(body, context: @context.merge({ base_url: "/userprofile" })),
+      )
     end
 
     def test_base_url_slash_with_tilde
       body = "<p>Hi, @jch!</p>"
       link = '<a href="/~jch" class="user-mention">@jch</a>'
 
-      assert_equal("<p>Hi, #{link}!</p>",
-        @filter.call(body, context: @context.merge({ base_url: "/~" })))
+      assert_equal(
+        "<p>Hi, #{link}!</p>",
+        @filter.call(body, context: @context.merge({ base_url: "/~" })),
+      )
     end
 
     def test_matches_usernames_in_body
@@ -190,8 +202,10 @@ def test_username_pattern_can_be_customized
 
       link = '<a href="/_abc" class="user-mention">@_abc</a>'
 
-      assert_equal("<p>#{link}: test.</p>",
-        res)
+      assert_equal(
+        "<p>#{link}: test.</p>",
+        res,
+      )
     end
 
     def test_filter_does_not_create_a_new_object_for_default_username_pattern
diff --git a/test/html_pipeline/node_filter/syntax_highlight_filter_test.rb b/test/html_pipeline/node_filter/syntax_highlight_filter_test.rb
new file mode 100644
index 00000000..a2b47e0b
--- /dev/null
+++ b/test/html_pipeline/node_filter/syntax_highlight_filter_test.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+SyntaxHighlightFilter = HTMLPipeline::NodeFilter::SyntaxHighlightFilter
+
+class HTMLPipeline
+  class SyntaxHighlightFilterTest < Minitest::Test
+    def test_highlight_default
+      result = SyntaxHighlightFilter.call(\
+        "<pre>hello</pre>", context: { highlight: "coffeescript" }
+      )
+
+      doc = Nokogiri.parse(result)
+
+      refute_empty(doc.css(".highlight"))
+      refute_empty(doc.css(".highlight-coffeescript"))
+    end
+
+    def test_highlight_default_will_not_override
+      result = SyntaxHighlightFilter.call(\
+        "<pre lang='c'>hello</pre>",  context: { highlight: "coffeescript" }
+      )
+
+      doc = Nokogiri.parse(result)
+
+      assert_empty(doc.css(".highlight-coffeescript"))
+      refute_empty(doc.css(".highlight-c"))
+    end
+
+    def test_highlight_does_not_remove_pre_tag
+      result = SyntaxHighlightFilter.call(\
+        "<pre lang='c'>hello</pre>",  context: { highlight: "coffeescript" }
+      )
+
+      doc = Nokogiri.parse(result)
+
+      refute_empty(doc.css("pre"))
+    end
+
+    def test_highlight_allows_optional_scope
+      result = SyntaxHighlightFilter.call(\
+        "<pre lang='c'>hello</pre>",  context: { highlight: "coffeescript", scope: "test-scope" }
+      )
+
+      doc = Nokogiri.parse(result)
+
+      refute_empty(doc.css("pre.test-scope"))
+    end
+
+    def test_highlight_keeps_the_pre_tags_lang
+      result = SyntaxHighlightFilter.call(\
+        "<pre lang='c'>hello</pre>",  context: { highlight: "coffeescript" }
+      )
+
+      doc = Nokogiri.parse(result)
+
+      refute_empty(doc.css("pre[lang=c]"))
+    end
+  end
+end
diff --git a/test/html_pipeline/node_filter/table_of_contents_filter_test.rb b/test/html_pipeline/node_filter/table_of_contents_filter_test.rb
index 33b62889..1d651dcc 100644
--- a/test/html_pipeline/node_filter/table_of_contents_filter_test.rb
+++ b/test/html_pipeline/node_filter/table_of_contents_filter_test.rb
@@ -136,12 +136,14 @@ def test_toc_is_complete
         STR
 
         result = TocPipeline.call(orig)[:toc]
-        expected = [{ href: "#funky-president-by-james-brown", text: "&quot;Funky President&quot; by James Brown" },
-                    { href: "#its-my-thing-by-marva-whitney", text: "&quot;It's My Thing&quot; by Marva Whitney" },
-                    { href: "#boogie-back-by-roy-ayers", text: "&quot;Boogie Back&quot; by Roy Ayers" },
-                    { href: "#feel-good-by-fancy", text: "&quot;Feel Good&quot; by Fancy" },
-                    { href: "#funky-drummer-by-james-brown", text: "&quot;Funky Drummer&quot; by James Brown" },
-                    { href: "#ruthless-villain-by-eazy-e", text: "&quot;Ruthless Villain&quot; by Eazy-E" },]
+        expected = [
+          { href: "#funky-president-by-james-brown", text: "&quot;Funky President&quot; by James Brown" },
+          { href: "#its-my-thing-by-marva-whitney", text: "&quot;It's My Thing&quot; by Marva Whitney" },
+          { href: "#boogie-back-by-roy-ayers", text: "&quot;Boogie Back&quot; by Roy Ayers" },
+          { href: "#feel-good-by-fancy", text: "&quot;Feel Good&quot; by Fancy" },
+          { href: "#funky-drummer-by-james-brown", text: "&quot;Funky Drummer&quot; by James Brown" },
+          { href: "#ruthless-villain-by-eazy-e", text: "&quot;Ruthless Villain&quot; by Eazy-E" },
+        ]
 
         0..6.times do |i|
              assert_equal(expected[i], result[i])
@@ -157,10 +159,14 @@ def test_anchors_with_utf8_characters
 
         rendered_h1s = Nokogiri::HTML(TocPipeline.call(orig)[:output]).search("h1").map(&:to_s)
 
-        assert_equal("<h1>\n<a href=\"#%E6%97%A5%E6%9C%AC%E8%AA%9E\" aria-hidden=\"true\" id=\"%E6%97%A5%E6%9C%AC%E8%AA%9E\" class=\"anchor\"><span aria-hidden=\"true\" class=\"anchor\"></span></a>日本語</h1>",
-          rendered_h1s[0])
-        assert_equal("<h1>\n<a href=\"#%D1%80%D1%83%D1%81%D1%81%D0%BA%D0%B8%D0%B9\" aria-hidden=\"true\" id=\"%D1%80%D1%83%D1%81%D1%81%D0%BA%D0%B8%D0%B9\" class=\"anchor\"><span aria-hidden=\"true\" class=\"anchor\"></span></a>Русский</h1>",
-          rendered_h1s[1])
+        assert_equal(
+          "<h1>\n<a href=\"#%E6%97%A5%E6%9C%AC%E8%AA%9E\" aria-hidden=\"true\" id=\"%E6%97%A5%E6%9C%AC%E8%AA%9E\" class=\"anchor\"><span aria-hidden=\"true\" class=\"anchor\"></span></a>日本語</h1>",
+          rendered_h1s[0],
+        )
+        assert_equal(
+          "<h1>\n<a href=\"#%D1%80%D1%83%D1%81%D1%81%D0%BA%D0%B8%D0%B9\" aria-hidden=\"true\" id=\"%D1%80%D1%83%D1%81%D1%81%D0%BA%D0%B8%D0%B9\" class=\"anchor\"><span aria-hidden=\"true\" class=\"anchor\"></span></a>Русский</h1>",
+          rendered_h1s[1],
+        )
       end
 
       def test_toc_with_utf8_characters
@@ -172,10 +178,16 @@ def test_toc_with_utf8_characters
 
         result = TocPipeline.call(orig)[:toc]
 
-        expected = [{ href: "#%E6%97%A5%E6%9C%AC%E8%AA%9E",
-                      text: "日本語", },
-                    { href: "#%D1%80%D1%83%D1%81%D1%81%D0%BA%D0%B8%D0%B9",
-                      text: "Русский", },]
+        expected = [
+          {
+            href: "#%E6%97%A5%E6%9C%AC%E8%AA%9E",
+            text: "日本語",
+          },
+          {
+            href: "#%D1%80%D1%83%D1%81%D1%81%D0%BA%D0%B8%D0%B9",
+            text: "Русский",
+          },
+        ]
 
         0..2.times do |i|
           assert_equal(expected[i], result[i])
diff --git a/test/html_pipeline/node_filter/team_mention_filter_test.rb b/test/html_pipeline/node_filter/team_mention_filter_test.rb
index 4c93dbab..44bb3f59 100644
--- a/test/html_pipeline/node_filter/team_mention_filter_test.rb
+++ b/test/html_pipeline/node_filter/team_mention_filter_test.rb
@@ -8,10 +8,12 @@ def setup
       @filter = HTMLPipeline::NodeFilter::TeamMentionFilter
 
       @pipeline =
-        HTMLPipeline.new(convert_filter: HTMLPipeline::ConvertFilter::MarkdownFilter.new,
+        HTMLPipeline.new(
+          convert_filter: HTMLPipeline::ConvertFilter::MarkdownFilter.new,
           node_filters: [
             HTMLPipeline::NodeFilter::TeamMentionFilter.new,
-          ])
+          ],
+        )
     end
 
     def mentioned_teams(body)
@@ -26,8 +28,10 @@ def test_filtering_plain_text
 
       link = '<a href="/github/team" class="team-mention">@github/team</a>'
 
-      assert_equal("<p>#{link}: check it out.</p>",
-        res)
+      assert_equal(
+        "<p>#{link}: check it out.</p>",
+        res,
+      )
     end
 
     def test_not_replacing_mentions_in_pre_tags
@@ -65,39 +69,49 @@ def test_html_injection
       body = "<p>@github/team &lt;script>alert(0)&lt;/script></p>"
       link = '<a href="/github/team" class="team-mention">@github/team</a>'
 
-      assert_equal("<p>#{link} &lt;script>alert(0)&lt;/script></p>",
-        @filter.call(body, context: { base_url: "/" }))
+      assert_equal(
+        "<p>#{link} &lt;script>alert(0)&lt;/script></p>",
+        @filter.call(body, context: { base_url: "/" }),
+      )
     end
 
     def test_links_to_nothing_with_user_mention
       body = "<p>Hi, @kneath</p>"
 
-      assert_equal("<p>Hi, @kneath</p>",
-        @filter.call(body, context: { base_url: "/" }))
+      assert_equal(
+        "<p>Hi, @kneath</p>",
+        @filter.call(body, context: { base_url: "/" }),
+      )
     end
 
     def test_base_url_slash
       body = "<p>Hi, @github/team!</p>"
       link = '<a href="/github/team" class="team-mention">@github/team</a>'
 
-      assert_equal("<p>Hi, #{link}!</p>",
-        @filter.call(body, context: { base_url: "/" }))
+      assert_equal(
+        "<p>Hi, #{link}!</p>",
+        @filter.call(body, context: { base_url: "/" }),
+      )
     end
 
     def test_base_url_under_custom_route
       body = "<p>Hi, @org/team!</p>"
       link = '<a href="www.github.com/org/team" class="team-mention">@org/team</a>'
 
-      assert_equal("<p>Hi, #{link}!</p>",
-        @filter.call(body, context: { base_url: "www.github.com" }))
+      assert_equal(
+        "<p>Hi, #{link}!</p>",
+        @filter.call(body, context: { base_url: "www.github.com" }),
+      )
     end
 
     def test_base_url_slash_with_tilde
       body = "<p>Hi, @github/team!</p>"
       link = '<a href="/~github/team" class="team-mention">@github/team</a>'
 
-      assert_equal("<p>Hi, #{link}!</p>",
-        @filter.call(body, context: { base_url: "/~" }))
+      assert_equal(
+        "<p>Hi, #{link}!</p>",
+        @filter.call(body, context: { base_url: "/~" }),
+      )
     end
 
     def test_multiple_team_mentions
@@ -105,8 +119,10 @@ def test_multiple_team_mentions
       link_whale = '<a href="/github/whale" class="team-mention">@github/whale</a>'
       link_donut = '<a href="/github/donut" class="team-mention">@github/donut</a>'
 
-      assert_equal("<p>Hi, #{link_whale} and #{link_donut}!</p>",
-        @filter.call(body))
+      assert_equal(
+        "<p>Hi, #{link_whale} and #{link_donut}!</p>",
+        @filter.call(body),
+      )
     end
 
     def test_matches_teams_in_body
@@ -206,8 +222,10 @@ def test_team_pattern_can_be_customized
 
       link = '<a href="/_abc/XYZ" class="team-mention">@_abc/XYZ</a>'
 
-      assert_equal("<p>#{link}: test</p>",
-        res)
+      assert_equal(
+        "<p>#{link}: test</p>",
+        res,
+      )
     end
 
     def test_mention_link_filter
diff --git a/test/html_pipeline/text_filter/image_filter_test.rb b/test/html_pipeline/text_filter/image_filter_test.rb
index be67c278..bc1a0709 100644
--- a/test/html_pipeline/text_filter/image_filter_test.rb
+++ b/test/html_pipeline/text_filter/image_filter_test.rb
@@ -11,33 +11,45 @@ def setup
     end
 
     def test_jpg
-      assert_equal(%(<img src="http://example.com/test.jpg" alt=""/>),
-        @filter.call(%(http://example.com/test.jpg)))
+      assert_equal(
+        %(<img src="http://example.com/test.jpg" alt=""/>),
+        @filter.call(%(http://example.com/test.jpg)),
+      )
     end
 
     def test_jpeg
-      assert_equal(%(<img src="http://example.com/test.jpeg" alt=""/>),
-        @filter.call(%(http://example.com/test.jpeg)))
+      assert_equal(
+        %(<img src="http://example.com/test.jpeg" alt=""/>),
+        @filter.call(%(http://example.com/test.jpeg)),
+      )
     end
 
     def test_bmp
-      assert_equal(%(<img src="http://example.com/test.bmp" alt=""/>),
-        @filter.call(%(http://example.com/test.bmp)))
+      assert_equal(
+        %(<img src="http://example.com/test.bmp" alt=""/>),
+        @filter.call(%(http://example.com/test.bmp)),
+      )
     end
 
     def test_gif
-      assert_equal(%(<img src="http://example.com/test.gif" alt=""/>),
-        @filter.call(%(http://example.com/test.gif)))
+      assert_equal(
+        %(<img src="http://example.com/test.gif" alt=""/>),
+        @filter.call(%(http://example.com/test.gif)),
+      )
     end
 
     def test_png
-      assert_equal(%(<img src="http://example.com/test.png" alt=""/>),
-        @filter.call(%(http://example.com/test.png)))
+      assert_equal(
+        %(<img src="http://example.com/test.png" alt=""/>),
+        @filter.call(%(http://example.com/test.png)),
+      )
     end
 
     def test_https_url
-      assert_equal(%(<img src="https://example.com/test.png" alt=""/>),
-        @filter.call(%(https://example.com/test.png)))
+      assert_equal(
+        %(<img src="https://example.com/test.png" alt=""/>),
+        @filter.call(%(https://example.com/test.png)),
+      )
     end
   end
 end
diff --git a/test/html_pipeline/text_filter/plain_text_input_filter_test.rb b/test/html_pipeline/text_filter/plain_text_input_filter_test.rb
index 742afab9..79bec1fc 100644
--- a/test/html_pipeline/text_filter/plain_text_input_filter_test.rb
+++ b/test/html_pipeline/text_filter/plain_text_input_filter_test.rb
@@ -21,8 +21,10 @@ def test_wraps_input_in_a_div_element
     def test_html_escapes_plain_text_input
       doc = PlainTextInputFilter.call("See: <http://example.org>", context: {})
 
-      assert_equal("<div>See: &lt;http://example.org&gt;</div>",
-        doc.to_s)
+      assert_equal(
+        "<div>See: &lt;http://example.org&gt;</div>",
+        doc.to_s,
+      )
     end
   end
 end
diff --git a/test/sanitization_filter_test.rb b/test/sanitization_filter_test.rb
index 5e26f4ff..25a12f56 100644
--- a/test/sanitization_filter_test.rb
+++ b/test/sanitization_filter_test.rb
@@ -105,9 +105,13 @@ def test_allow_svg_elements_to_be_added
 
       assert_equal("\n", html)
 
-      config = { elements: ["svg", "circle"],
-                 attributes: { "svg" => ["width"],
-                               "circle" => ["cx", "cy", "r"], }, }
+      config = {
+        elements: ["svg", "circle"],
+        attributes: {
+          "svg" => ["width"],
+          "circle" => ["cx", "cy", "r"],
+        },
+      }
 
       result = <<~FRAG
         <svg width="100">