diff --git a/test/fixtures/aria/input.html b/test/fixtures/aria/input.html
new file mode 100644
index 0000000..f3653c4
--- /dev/null
+++ b/test/fixtures/aria/input.html
@@ -0,0 +1,16 @@
+<!doctype html>
+<html lang="en"><meta charset="utf-8"><title>ARIA</title>
+<form>
+<fieldset><legend>Login</legend>
+<div>
+<label for="username">Username</label>
+<input id="username" aria-describedby="username-tip" required>
+<div role="tooltip" id="username-tip">Your username is your email address</div>
+</div>
+<div>
+<label for="password">Password</label>
+<input id="password" aria-describedby="password-tip" required>
+<div role="tooltip" id="password-tip">Was emailed to you when you signed up</div>
+</div>
+</fieldset>
+</form>
diff --git a/test/fixtures/aria/output.html b/test/fixtures/aria/output.html
new file mode 100644
index 0000000..f79fe92
--- /dev/null
+++ b/test/fixtures/aria/output.html
@@ -0,0 +1,24 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>ARIA</title>
+          <style>
          .commit-tease,
          .user-profile-mini-avatar,
          .avatar,
          .vcard-details,
          .signup-prompt-bg {
            display: none !IMPORTANT;
          }
        </style>
         <script>
          document.addEventListener('DOMContentLoaded', function() {
            this.querySelectorAll('a').forEach(anchor => {
              anchor.addEventListener('click', e => {
                e.preventDefault();

                const redact = new URLSearchParams(window.location.search).get('redact');
                const hasExistingParams = anchor.href.includes('?');
                window.location.href = anchor.href + (hasExistingParams ? `&redact=${redact}` : `?redact=${redact}`);
              });
            });
          });
        </script>
 </head>
+  <body>
+    <form>
+      <fieldset>
+        <legend>Login</legend>
+        <div>
+          <label for="username">Username</label>
+          <input id="username" aria-describedby="username-tip" required>
+          <div role="tooltip" id="username-tip">Your username is your email address</div>
+        </div>
+        <div>
+          <label for="password">Password</label>
+          <input id="password" aria-describedby="password-tip" required>
+          <div role="tooltip" id="password-tip">Was emailed to you when you signed up</div>
+        </div>
+      </fieldset>
+    </form>
+  </body>
+</html>
diff --git a/test/fixtures/html-in-svg-in-html/input.html b/test/fixtures/html-in-svg-in-html/input.html
new file mode 100644
index 0000000..eb574d3
--- /dev/null
+++ b/test/fixtures/html-in-svg-in-html/input.html
@@ -0,0 +1,9 @@
+<!doctype html>
+<meta charset="utf-8"><title>SVG</title>
+<h1>HTML in SVG in HTML</h1>
+<svg xmlns="http://www.w3.org/2000/svg" width="400" height="300" viewBox="0 0 400 300">
+<switch>
+<foreignObject width="200" height="100" requiredExtensions="http://www.w3.org/1999/xhtml"><p xmlns="http://www.w3.org/1999/xhtml">Here is an HTML paragraph that requires word wrap</p></foreignObject>
+<text font-size="16"><tspan x="0" y="14">Here is an SVG paragraph</tspan><tspan x="0" y="32">that requires word wrap.</tspan></text>
+</switch>
+</svg>
diff --git a/test/fixtures/html-in-svg-in-html/output.html b/test/fixtures/html-in-svg-in-html/output.html
new file mode 100644
index 0000000..40232f4
--- /dev/null
+++ b/test/fixtures/html-in-svg-in-html/output.html
@@ -0,0 +1,21 @@
+<!doctype html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>SVG</title>
+          <style>
          .commit-tease,
          .user-profile-mini-avatar,
          .avatar,
          .vcard-details,
          .signup-prompt-bg {
            display: none !IMPORTANT;
          }
        </style>
         <script>
          document.addEventListener('DOMContentLoaded', function() {
            this.querySelectorAll('a').forEach(anchor => {
              anchor.addEventListener('click', e => {
                e.preventDefault();

                const redact = new URLSearchParams(window.location.search).get('redact');
                const hasExistingParams = anchor.href.includes('?');
                window.location.href = anchor.href + (hasExistingParams ? `&redact=${redact}` : `?redact=${redact}`);
              });
            });
          });
        </script>
 </head>
+  <body>
+    <h1>HTML in SVG in HTML</h1>
+    <svg xmlns="http://www.w3.org/2000/svg" width="400" height="300" viewBox="0 0 400 300">
+      <switch>
+        <foreignObject width="200" height="100" requiredExtensions="http://www.w3.org/1999/xhtml">
+          <p xmlns="http://www.w3.org/1999/xhtml">Here is an HTML paragraph that requires word wrap</p>
+        </foreignObject>
+        <text font-size="16">
+          <tspan x="0" y="14">Here is an SVG paragraph</tspan>
+          <tspan x="0" y="32">that requires word wrap.</tspan>
+        </text>
+      </switch>
+    </svg>
+  </body>
+</html>
diff --git a/test/fixtures/mathml/input.html b/test/fixtures/mathml/input.html
new file mode 100644
index 0000000..b227647
--- /dev/null
+++ b/test/fixtures/mathml/input.html
@@ -0,0 +1,23 @@
+<!doctype html>
+<title>MathML</title>
+<h1>The quadratic formula</h1>
+<p>
+<math>
+<mi>x</mi>
+<mo>=</mo>
+<mfrac>
+<mrow>
+<mo form="prefix">−</mo> <mi>b</mi>
+<mo>±</mo>
+<msqrt>
+<msup> <mi>b</mi> <mn>2</mn> </msup>
+<mo>−</mo>
+<mn>4</mn> <mo>⁢</mo> <mi>a</mi> <mo>⁢</mo> <mi>c</mi>
+</msqrt>
+</mrow>
+<mrow>
+<mn>2</mn> <mo>⁢</mo> <mi>a</mi>
+</mrow>
+</mfrac>
+</math>
+</p>
diff --git a/test/fixtures/mathml/output.html b/test/fixtures/mathml/output.html
new file mode 100644
index 0000000..854d9dd
--- /dev/null
+++ b/test/fixtures/mathml/output.html
@@ -0,0 +1,39 @@
+<!doctype html>
+<html>
+  <head>
+    <title>MathML</title>
+          <style>
          .commit-tease,
          .user-profile-mini-avatar,
          .avatar,
          .vcard-details,
          .signup-prompt-bg {
            display: none !IMPORTANT;
          }
        </style>
         <script>
          document.addEventListener('DOMContentLoaded', function() {
            this.querySelectorAll('a').forEach(anchor => {
              anchor.addEventListener('click', e => {
                e.preventDefault();

                const redact = new URLSearchParams(window.location.search).get('redact');
                const hasExistingParams = anchor.href.includes('?');
                window.location.href = anchor.href + (hasExistingParams ? `&redact=${redact}` : `?redact=${redact}`);
              });
            });
          });
        </script>
 </head>
+  <body>
+    <h1>The quadratic formula</h1>
+    <p>
+      <math>
+        <mi>x</mi>
+        <mo>=</mo>
+        <mfrac>
+          <mrow>
+            <mo form="prefix">−</mo>
+            <mi>b</mi>
+            <mo>±</mo>
+            <msqrt>
+              <msup>
+                <mi>b</mi>
+                <mn>2</mn>
+              </msup>
+              <mo>−</mo>
+              <mn>4</mn>
+              <mo>⁢</mo>
+              <mi>a</mi>
+              <mo>⁢</mo>
+              <mi>c</mi>
+            </msqrt>
+          </mrow>
+          <mrow>
+            <mn>2</mn>
+            <mo>⁢</mo>
+            <mi>a</mi>
+          </mrow>
+        </mfrac>
+      </math>
+    </p>
+  </body>
+</html>
diff --git a/test/fixtures/svg/input.html b/test/fixtures/svg/input.html
new file mode 100644
index 0000000..8a12ecc
--- /dev/null
+++ b/test/fixtures/svg/input.html
@@ -0,0 +1,7 @@
+<!doctype html>
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 200 200">
+<title>Variable: shape</title>
+<rect x="55" y="35" width="40" height="40"/>
+<circle cx="75" cy="110" r="25"/>
+<path d="M 50 145 L 100 145 L 75 185 z"/>
+</svg>
diff --git a/test/fixtures/svg/output.html b/test/fixtures/svg/output.html
new file mode 100644
index 0000000..a4ccb1d
--- /dev/null
+++ b/test/fixtures/svg/output.html
@@ -0,0 +1,12 @@
+<!doctype html>
+<html>
+  <head>        <style>
          .commit-tease,
          .user-profile-mini-avatar,
          .avatar,
          .vcard-details,
          .signup-prompt-bg {
            display: none !IMPORTANT;
          }
        </style>
         <script>
          document.addEventListener('DOMContentLoaded', function() {
            this.querySelectorAll('a').forEach(anchor => {
              anchor.addEventListener('click', e => {
                e.preventDefault();

                const redact = new URLSearchParams(window.location.search).get('redact');
                const hasExistingParams = anchor.href.includes('?');
                window.location.href = anchor.href + (hasExistingParams ? `&redact=${redact}` : `?redact=${redact}`);
              });
            });
          });
        </script>
 </head>
+  <body>
+    <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 200 200">
+      <title>Variable: shape</title>
+      <rect x="55" y="35" width="40" height="40"></rect>
+      <circle cx="75" cy="110" r="25"></circle>
+      <path d="M 50 145 L 100 145 L 75 185 z"></path>
+    </svg>
+  </body>
+</html>
diff --git a/test/fixtures/xhtml/input.html b/test/fixtures/xhtml/input.html
new file mode 100644
index 0000000..0aad016
--- /dev/null
+++ b/test/fixtures/xhtml/input.html
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<html xmlns="http://www.w3.org/1999/xhtml">
+<title>Example document</title>
+<p>Example paragraph</p>
diff --git a/test/fixtures/xhtml/output.html b/test/fixtures/xhtml/output.html
new file mode 100644
index 0000000..a9270ca
--- /dev/null
+++ b/test/fixtures/xhtml/output.html
@@ -0,0 +1,9 @@
+<!--?xml version="1.0" encoding="UTF-8"?-->
+<html xmlns="http://www.w3.org/1999/xhtml">
+  <head>
+    <title>Example document</title>
+          <style>
          .commit-tease,
          .user-profile-mini-avatar,
          .avatar,
          .vcard-details,
          .signup-prompt-bg {
            display: none !IMPORTANT;
          }
        </style>
         <script>
          document.addEventListener('DOMContentLoaded', function() {
            this.querySelectorAll('a').forEach(anchor => {
              anchor.addEventListener('click', e => {
                e.preventDefault();

                const redact = new URLSearchParams(window.location.search).get('redact');
                const hasExistingParams = anchor.href.includes('?');
                window.location.href = anchor.href + (hasExistingParams ? `&redact=${redact}` : `?redact=${redact}`);
              });
            });
          });
        </script>
 </head>
+  <body>
+    <p>Example paragraph</p>
+  </body>
+</html>
