diff --git a/package-lock.json b/package-lock.json
index 1b7b0c7e52..ba554ff58d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -159,6 +159,12 @@
       "integrity": "sha1-ibTRmasr7kneFk6gK4nORi1xt2c=",
       "dev": true
     },
+    "boolbase": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/boolbase/-/boolbase-1.0.0.tgz",
+      "integrity": "sha1-aN/1++YMUes3cl6p4+0xDcwed24=",
+      "dev": true
+    },
     "brace-expansion": {
       "version": "1.1.8",
       "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-1.1.8.tgz",
@@ -198,6 +204,31 @@
       "integrity": "sha512-mT8iDcrh03qDGRRmoA2hmBJnxpllMR+0/0qlzjqZES6NdiWDcZkCNAk4rPFZ9Q85r27unkiNNg8ZOiwZXBHwcA==",
       "dev": true
     },
+    "cheerio": {
+      "version": "1.0.0-rc.3",
+      "resolved": "https://registry.npmjs.org/cheerio/-/cheerio-1.0.0-rc.3.tgz",
+      "integrity": "sha512-0td5ijfUPuubwLUu0OBoe98gZj8C/AA+RW3v67GPlGOrvxWjZmBXiBCRU+I8VEiNyJzjth40POfHiz2RB3gImA==",
+      "dev": true,
+      "requires": {
+        "css-select": "~1.2.0",
+        "dom-serializer": "~0.1.1",
+        "entities": "~1.1.1",
+        "htmlparser2": "^3.9.1",
+        "lodash": "^4.15.0",
+        "parse5": "^3.0.1"
+      },
+      "dependencies": {
+        "parse5": {
+          "version": "3.0.3",
+          "resolved": "https://registry.npmjs.org/parse5/-/parse5-3.0.3.tgz",
+          "integrity": "sha512-rgO9Zg5LLLkfJF9E6CCmXlSE4UVceloys8JrFqCcHloC3usd/kJCyPDwH2SOlzix2j3xaP9sUX3e8+kvkuleAA==",
+          "dev": true,
+          "requires": {
+            "@types/node": "*"
+          }
+        }
+      }
+    },
     "cli-cursor": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/cli-cursor/-/cli-cursor-2.1.0.tgz",
@@ -340,6 +371,24 @@
         "which": "^1.2.9"
       }
     },
+    "css-select": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmjs.org/css-select/-/css-select-1.2.0.tgz",
+      "integrity": "sha1-KzoRBTnFNV8c2NMUYj6HCxIeyFg=",
+      "dev": true,
+      "requires": {
+        "boolbase": "~1.0.0",
+        "css-what": "2.1",
+        "domutils": "1.5.1",
+        "nth-check": "~1.0.1"
+      }
+    },
+    "css-what": {
+      "version": "2.1.3",
+      "resolved": "https://registry.npmjs.org/css-what/-/css-what-2.1.3.tgz",
+      "integrity": "sha512-a+EPoD+uZiNfh+5fxw2nO9QwFa6nJe2Or35fGY6Ipw1R3R4AGz1d1TEZrCegvw2YTmZ0jXirGYlzxxpYSHwpEg==",
+      "dev": true
+    },
     "debug": {
       "version": "4.1.1",
       "resolved": "https://registry.npmjs.org/debug/-/debug-4.1.1.tgz",
@@ -376,6 +425,41 @@
         "esutils": "^2.0.2"
       }
     },
+    "dom-serializer": {
+      "version": "0.1.1",
+      "resolved": "https://registry.npmjs.org/dom-serializer/-/dom-serializer-0.1.1.tgz",
+      "integrity": "sha512-l0IU0pPzLWSHBcieZbpOKgkIn3ts3vAh7ZuFyXNwJxJXk/c4Gwj9xaTJwIDVQCXawWD0qb3IzMGH5rglQaO0XA==",
+      "dev": true,
+      "requires": {
+        "domelementtype": "^1.3.0",
+        "entities": "^1.1.1"
+      }
+    },
+    "domelementtype": {
+      "version": "1.3.1",
+      "resolved": "https://registry.npmjs.org/domelementtype/-/domelementtype-1.3.1.tgz",
+      "integrity": "sha512-BSKB+TSpMpFI/HOxCNr1O8aMOTZ8hT3pM3GQ0w/mWRmkhEDSFJkkyzz4XQsBV44BChwGkrDfMyjVD0eA2aFV3w==",
+      "dev": true
+    },
+    "domhandler": {
+      "version": "2.4.2",
+      "resolved": "https://registry.npmjs.org/domhandler/-/domhandler-2.4.2.tgz",
+      "integrity": "sha512-JiK04h0Ht5u/80fdLMCEmV4zkNh2BcoMFBmZ/91WtYZ8qVXSKjiw7fXMgFPnHcSZgOo3XdinHvmnDUeMf5R4wA==",
+      "dev": true,
+      "requires": {
+        "domelementtype": "1"
+      }
+    },
+    "domutils": {
+      "version": "1.5.1",
+      "resolved": "https://registry.npmjs.org/domutils/-/domutils-1.5.1.tgz",
+      "integrity": "sha1-3NhIiib1Y9YQeeSMn3t+Mjc2gs8=",
+      "dev": true,
+      "requires": {
+        "dom-serializer": "0",
+        "domelementtype": "1"
+      }
+    },
     "emoji-regex": {
       "version": "7.0.3",
       "resolved": "https://registry.npmjs.org/emoji-regex/-/emoji-regex-7.0.3.tgz",
@@ -860,6 +944,20 @@
       "integrity": "sha512-7T/BxH19zbcCTa8XkMlbK5lTo1WtgkFi3GvdWEyNuc4Vex7/9Dqbnpsf4JMydcfj9HCg4zUWFTL3Za6lapg5/w==",
       "dev": true
     },
+    "htmlparser2": {
+      "version": "3.10.1",
+      "resolved": "https://registry.npmjs.org/htmlparser2/-/htmlparser2-3.10.1.tgz",
+      "integrity": "sha512-IgieNijUMbkDovyoKObU1DUhm1iwNYE/fuifEoEHfd1oZKZDaONBSkal7Y01shxsM49R4XaMdGez3WnF9UfiCQ==",
+      "dev": true,
+      "requires": {
+        "domelementtype": "^1.3.1",
+        "domhandler": "^2.3.0",
+        "domutils": "^1.5.1",
+        "entities": "^1.1.1",
+        "inherits": "^2.0.1",
+        "readable-stream": "^3.1.1"
+      }
+    },
     "http-basic": {
       "version": "7.0.0",
       "resolved": "https://registry.npmjs.org/http-basic/-/http-basic-7.0.0.tgz",
@@ -1221,6 +1319,15 @@
         "validate-npm-package-license": "^3.0.1"
       }
     },
+    "nth-check": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/nth-check/-/nth-check-1.0.2.tgz",
+      "integrity": "sha512-WeBOdju8SnzPN5vTUJYxYUxLeXpCaVP5i5e0LF8fg7WORF2Wd7wFX/pk0tYZk7s8T+J7VLy0Da6J1+wCT0AtHg==",
+      "dev": true,
+      "requires": {
+        "boolbase": "~1.0.0"
+      }
+    },
     "once": {
       "version": "1.4.0",
       "resolved": "https://registry.npmjs.org/once/-/once-1.4.0.tgz",
@@ -1433,6 +1540,17 @@
         "read-pkg": "^2.0.0"
       }
     },
+    "readable-stream": {
+      "version": "3.3.0",
+      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.3.0.tgz",
+      "integrity": "sha512-EsI+s3k3XsW+fU8fQACLN59ky34AZ14LoeVZpYwmZvldCFo0r0gnelwF2TcMjLor/BTL5aDJVBMkss0dthToPw==",
+      "dev": true,
+      "requires": {
+        "inherits": "^2.0.3",
+        "string_decoder": "^1.1.1",
+        "util-deprecate": "^1.0.1"
+      }
+    },
     "regexpp": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/regexpp/-/regexpp-2.0.1.tgz",
@@ -1607,6 +1725,15 @@
       "integrity": "sha1-q6Nt4I3O5qWjN9SbLqHaGyj8Ds8=",
       "dev": true
     },
+    "string_decoder": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.2.0.tgz",
+      "integrity": "sha512-6YqyX6ZWEYguAxgZzHGL7SsCeGx3V2TtOTqZz1xSTSWnqsbWwbptafNyvf/ACquZUXV3DANr5BDIwNYe1mN42w==",
+      "dev": true,
+      "requires": {
+        "safe-buffer": "~5.1.0"
+      }
+    },
     "strip-ansi": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/strip-ansi/-/strip-ansi-4.0.0.tgz",
diff --git a/package.json b/package.json
index 916f6a177b..43cea559fc 100644
--- a/package.json
+++ b/package.json
@@ -30,6 +30,7 @@
   ],
   "devDependencies": {
     "@markedjs/html-differ": "^2.0.1",
+    "cheerio": "^1.0.0-rc.3",
     "commonmark": "0.x",
     "eslint": "^5.15.1",
     "eslint-config-standard": "^12.0.0",
diff --git a/test/specs/gfm/getSpecs.js b/test/specs/gfm/getSpecs.js
new file mode 100644
index 0000000000..2746bdbbcb
--- /dev/null
+++ b/test/specs/gfm/getSpecs.js
@@ -0,0 +1,44 @@
+const fetch = require('node-fetch');
+const cheerio = require('cheerio');
+const marked = require('../../../');
+const htmlDiffer = require('../../helpers/html-differ.js');
+const fs = require('fs');
+
+fetch('https://github.github.com/gfm/')
+  .then(res => res.text())
+  .then(html => cheerio.load(html))
+  .then($ => {
+    const version = $('.version').text().match(/\d+\.\d+/)[0];
+    if (!version) {
+      throw new Error('No version found');
+    }
+    const specs = [];
+    $('.extension').each((i, ext) => {
+      const section = $('.definition', ext).text().trim().replace(/^\d+\.\d+(.*?) \(extension\)[\s\S]*$/, '$1');
+      $('.example', ext).each((j, exa) => {
+        const example = +$(exa).attr('id').replace(/\D/g, '');
+        const markdown = $('.language-markdown', exa).text().trim();
+        const html = $('.language-html', exa).text().trim();
+        specs.push({
+          section,
+          html,
+          markdown,
+          example
+        });
+      });
+    });
+
+    return [version, specs];
+  })
+  .then(([version, specs]) => {
+    specs.forEach(spec => {
+      const html = marked(spec.markdown, {gfm: true});
+      if (!htmlDiffer.isEqual(html, spec.html)) {
+        spec.shouldFail = true;
+      }
+    });
+    fs.writeFileSync(`gfm.${version}.json`, JSON.stringify(specs, null, 2) + '\n');
+  })
+  .catch((err) => {
+    console.error(err);
+  });
diff --git a/test/specs/gfm/gfm.0.28.json b/test/specs/gfm/gfm.0.29.json
similarity index 86%
rename from test/specs/gfm/gfm.0.28.json
rename to test/specs/gfm/gfm.0.29.json
index 75bffc64ce..7d1d43e4b6 100644
--- a/test/specs/gfm/gfm.0.28.json
+++ b/test/specs/gfm/gfm.0.29.json
@@ -1,153 +1,147 @@
 [
   {
     "section": "Tables",
-    "html": "<table>\n<thead>\n<tr>\n<th>foo</th>\n<th>bar</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>baz</td>\n<td>bim</td>\n</tr></tbody></table>",
+    "html": "<table>\n<thead>\n<tr>\n<th>foo</th>\n<th>bar</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>baz</td>\n<td>bim</td>\n</tr>\n</tbody>\n</table>",
     "markdown": "| foo | bar |\n| --- | --- |\n| baz | bim |",
-    "example": 191
+    "example": 198
   },
   {
     "section": "Tables",
-    "html": "<table>\n<thead>\n<tr>\n<th align=\"center\">abc</th>\n<th align=\"right\">defghi</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td align=\"center\">bar</td>\n<td align=\"right\">baz</td>\n</tr></tbody></table>",
+    "html": "<table>\n<thead>\n<tr>\n<th align=\"center\">abc</th>\n<th align=\"right\">defghi</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td align=\"center\">bar</td>\n<td align=\"right\">baz</td>\n</tr>\n</tbody>\n</table>",
     "markdown": "| abc | defghi |\n:-: | -----------:\nbar | baz",
-    "example": 192
+    "example": 199
   },
   {
     "section": "Tables",
-    "html": "<table>\n<thead>\n<tr>\n<th>f|oo</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>b <code>|</code> az</td>\n</tr>\n<tr>\n<td>b <strong>|</strong> im</td>\n</tr></tbody></table>",
+    "html": "<table>\n<thead>\n<tr>\n<th>f|oo</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>b <code>|</code> az</td>\n</tr>\n<tr>\n<td>b <strong>|</strong> im</td>\n</tr>\n</tbody>\n</table>",
     "markdown": "| f\\|oo  |\n| ------ |\n| b `\\|` az |\n| b **\\|** im |",
-    "example": 193
+    "example": 200
   },
   {
     "section": "Tables",
-    "html": "<table>\n<thead>\n<tr>\n<th>abc</th>\n<th>def</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>bar</td>\n<td>baz</td>\n</tr></tbody></table>\n<blockquote>\n<p>bar</p>\n</blockquote>",
+    "html": "<table>\n<thead>\n<tr>\n<th>abc</th>\n<th>def</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>bar</td>\n<td>baz</td>\n</tr>\n</tbody>\n</table>\n<blockquote>\n<p>bar</p>\n</blockquote>",
     "markdown": "| abc | def |\n| --- | --- |\n| bar | baz |\n> bar",
-    "example": 194
+    "example": 201
   },
   {
     "section": "Tables",
-    "html": "<table>\n<thead>\n<tr>\n<th>abc</th>\n<th>def</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>bar</td>\n<td>baz</td>\n</tr>\n<tr>\n<td>bar</td>\n<td></td>\n</tr></tbody></table>\n<p>bar</p>",
+    "html": "<table>\n<thead>\n<tr>\n<th>abc</th>\n<th>def</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>bar</td>\n<td>baz</td>\n</tr>\n<tr>\n<td>bar</td>\n<td></td>\n</tr>\n</tbody>\n</table>\n<p>bar</p>",
     "markdown": "| abc | def |\n| --- | --- |\n| bar | baz |\nbar\n\nbar",
-    "example": 195
+    "example": 202
   },
   {
     "section": "Tables",
     "html": "<p>| abc | def |\n| --- |\n| bar |</p>",
     "markdown": "| abc | def |\n| --- |\n| bar |",
-    "example": 196
+    "example": 203
   },
   {
     "section": "Tables",
-    "html": "<table>\n<thead>\n<tr>\n<th>abc</th>\n<th>def</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>bar</td>\n<td></td>\n</tr>\n<tr>\n<td>bar</td>\n<td>baz</td>\n</tr></tbody></table>",
+    "html": "<table>\n<thead>\n<tr>\n<th>abc</th>\n<th>def</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>bar</td>\n<td></td>\n</tr>\n<tr>\n<td>bar</td>\n<td>baz</td>\n</tr>\n</tbody>\n</table>",
     "markdown": "| abc | def |\n| --- | --- |\n| bar |\n| bar | baz | boo |",
-    "example": 197
+    "example": 204
   },
   {
     "section": "Tables",
-    "html": "<table>\n<thead>\n<tr>\n<th>abc</th>\n<th>def</th>\n</tr>\n</thead></table>",
+    "html": "<table>\n<thead>\n<tr>\n<th>abc</th>\n<th>def</th>\n</tr>\n</thead>\n</table>",
     "markdown": "| abc | def |\n| --- | --- |",
-    "example": 198
+    "example": 205
   },
   {
     "section": "Task list items",
     "html": "<ul>\n<li><input disabled=\"\" type=\"checkbox\"> foo</li>\n<li><input checked=\"\" disabled=\"\" type=\"checkbox\"> bar</li>\n</ul>",
     "markdown": "- [ ] foo\n- [x] bar",
-    "example": 272
+    "example": 279
   },
   {
     "section": "Task list items",
     "html": "<ul>\n<li><input checked=\"\" disabled=\"\" type=\"checkbox\"> foo\n<ul>\n<li><input disabled=\"\" type=\"checkbox\"> bar</li>\n<li><input checked=\"\" disabled=\"\" type=\"checkbox\"> baz</li>\n</ul>\n</li>\n<li><input disabled=\"\" type=\"checkbox\"> bim</li>\n</ul>",
     "markdown": "- [x] foo\n  - [ ] bar\n  - [x] baz\n- [ ] bim",
-    "example": 273
+    "example": 280
   },
   {
     "section": "Strikethrough",
     "html": "<p><del>Hi</del> Hello, world!</p>",
-    "markdown": "~Hi~ Hello, world!",
-    "example": 469
-  },
-  {
-    "section": "Strikethrough",
-    "html": "<p>This <del>text</del> is <del>curious</del>.</p>",
-    "markdown": "This ~text~~~~ is ~~~~curious~.",
-    "example": 470
+    "markdown": "~~Hi~~ Hello, world!",
+    "example": 491
   },
   {
     "section": "Strikethrough",
     "html": "<p>This ~~has a</p>\n<p>new paragraph~~.</p>",
     "markdown": "This ~~has a\n\nnew paragraph~~.",
-    "example": 471
+    "example": 492
   },
   {
     "section": "Autolinks",
     "html": "<p><a href=\"http://www.commonmark.org\">www.commonmark.org</a></p>",
     "markdown": "www.commonmark.org",
-    "example": 597
+    "example": 621
   },
   {
     "section": "Autolinks",
     "html": "<p>Visit <a href=\"http://www.commonmark.org/help\">www.commonmark.org/help</a> for more information.</p>",
     "markdown": "Visit www.commonmark.org/help for more information.",
-    "example": 598
+    "example": 622
   },
   {
     "section": "Autolinks",
     "html": "<p>Visit <a href=\"http://www.commonmark.org\">www.commonmark.org</a>.</p>\n<p>Visit <a href=\"http://www.commonmark.org/a.b\">www.commonmark.org/a.b</a>.</p>",
     "markdown": "Visit www.commonmark.org.\n\nVisit www.commonmark.org/a.b.",
-    "example": 599
+    "example": 623
   },
   {
     "section": "Autolinks",
     "html": "<p><a href=\"http://www.google.com/search?q=Markup+(business)\">www.google.com/search?q=Markup+(business)</a></p>\n<p>(<a href=\"http://www.google.com/search?q=Markup+(business)\">www.google.com/search?q=Markup+(business)</a>)</p>",
     "markdown": "www.google.com/search?q=Markup+(business)\n\n(www.google.com/search?q=Markup+(business))",
-    "example": 600
+    "example": 624
   },
   {
     "section": "Autolinks",
     "html": "<p><a href=\"http://www.google.com/search?q=(business))+ok\">www.google.com/search?q=(business))+ok</a></p>",
     "markdown": "www.google.com/search?q=(business))+ok",
-    "example": 601
+    "example": 625
   },
   {
     "section": "Autolinks",
     "html": "<p><a href=\"http://www.google.com/search?q=commonmark&amp;hl=en\">www.google.com/search?q=commonmark&amp;hl=en</a></p>\n<p><a href=\"http://www.google.com/search?q=commonmark\">www.google.com/search?q=commonmark</a>&amp;hl;</p>",
     "markdown": "www.google.com/search?q=commonmark&hl=en\n\nwww.google.com/search?q=commonmark&hl;",
-    "example": 602
+    "example": 626
   },
   {
     "section": "Autolinks",
     "html": "<p><a href=\"http://www.commonmark.org/he\">www.commonmark.org/he</a>&lt;lp</p>",
     "markdown": "www.commonmark.org/he<lp",
-    "example": 603
+    "example": 627
   },
   {
     "section": "Autolinks",
     "html": "<p><a href=\"http://commonmark.org\">http://commonmark.org</a></p>\n<p>(Visit <a href=\"https://encrypted.google.com/search?q=Markup+(business)\">https://encrypted.google.com/search?q=Markup+(business)</a>)</p>\n<p>Anonymous FTP is available at <a href=\"ftp://foo.bar.baz\">ftp://foo.bar.baz</a>.</p>",
     "markdown": "http://commonmark.org\n\n(Visit https://encrypted.google.com/search?q=Markup+(business))\n\nAnonymous FTP is available at ftp://foo.bar.baz.",
-    "example": 604
+    "example": 628
   },
   {
     "section": "Autolinks",
     "html": "<p><a href=\"mailto:foo@bar.baz\">foo@bar.baz</a></p>",
     "markdown": "foo@bar.baz",
-    "example": 605
+    "example": 629
   },
   {
     "section": "Autolinks",
     "html": "<p>hello@mail+xyz.example isn't valid, but <a href=\"mailto:hello+xyz@mail.example\">hello+xyz@mail.example</a> is.</p>",
     "markdown": "hello@mail+xyz.example isn't valid, but hello+xyz@mail.example is.",
-    "example": 606
+    "example": 630
   },
   {
     "section": "Autolinks",
     "html": "<p><a href=\"mailto:a.b-c_d@a.b\">a.b-c_d@a.b</a></p>\n<p><a href=\"mailto:a.b-c_d@a.b\">a.b-c_d@a.b</a>.</p>\n<p>a.b-c_d@a.b-</p>\n<p>a.b-c_d@a.b_</p>",
     "markdown": "a.b-c_d@a.b\n\na.b-c_d@a.b.\n\na.b-c_d@a.b-\n\na.b-c_d@a.b_",
-    "example": 607
+    "example": 631
   },
   {
     "section": "Disallowed Raw HTML",
     "html": "<p><strong> &lt;title> &lt;style> <em></p>\n<blockquote>\n  &lt;xmp> is disallowed.  &lt;XMP> is also disallowed.\n</blockquote>",
     "markdown": "<strong> <title> <style> <em>\n\n<blockquote>\n  <xmp> is disallowed.  <XMP> is also disallowed.\n</blockquote>",
-    "example": 629,
+    "example": 653,
     "shouldFail": true
   }
 ]
diff --git a/test/specs/run-spec.js b/test/specs/run-spec.js
index 56a3f70a49..3af0aa4565 100644
--- a/test/specs/run-spec.js
+++ b/test/specs/run-spec.js
@@ -48,5 +48,5 @@ function runSpecs(title, file, options) {
   });
 };
 
-runSpecs('GFM 0.28', './gfm/gfm.0.28.json', {gfm: true});
+runSpecs('GFM 0.29', './gfm/gfm.0.29.json', {gfm: true});
 runSpecs('CommonMark 0.29', './commonmark/commonmark.0.29.json', {headerIds: false});