diff --git a/.npmignore b/.npmignore
new file mode 100644
index 0000000..6ca4202
--- /dev/null
+++ b/.npmignore
@@ -0,0 +1,2 @@
+test.*
+suite.*
diff --git a/suite.js b/suite.js
index 95d45db..7830e5a 100644
--- a/suite.js
+++ b/suite.js
@@ -102,7 +102,7 @@ function tests(isNative, TextEncoder, TextDecoder) {
 
 }
 
-if (window.NativeTextEncoder && window.NativeTextDecoder) {
+if (typeof NativeTextEncoder !== 'undefined' && typeof NativeTextDecoder !== 'undefined') {
   tests(true, NativeTextEncoder, NativeTextDecoder);
 }
 tests(false, TextEncoder, TextDecoder);
diff --git a/test.html b/test.html
index f8b9c9b..0833c89 100644
--- a/test.html
+++ b/test.html
@@ -43,73 +43,3 @@
 <script src="suite.js"></script>
 </body>
 </html>
-<!-- 
-<!DOCTYPE html>
-<html>
-<head>
-<script defer src="https://cdn.rawgit.com/mathiasbynens/utf8.js/5566334e/utf8.js"></script>
-<script type="module">
-</script>
-<script type="module">
-  import './polyfill.js';
-  import 'https://cdn.rawgit.com/inexorabletash/text-encoding/b98ab30b/lib/encoding.js';
-  const polyfill = module.exports;
-
-  import './text.js';
-
-  const runs = 1;
-  const dataUrl = './utf8_sequence_0-0xffff_assigned_printable.txt';
-
-  (async function() {
-    let text = await window.fetch(dataUrl).then((data) => data.text());
-    text = text.substr(0, 10000);
-
-    function testEncodeDecode(name, tenc, tdec) {
-      console.time(name + '.TextEncoder');
-      let saved;
-      const encoder = new tenc();
-      for (let i = 0; i < runs; ++i) {
-        const out = encoder.encode(text);
-        saved = out;
-      }
-      console.info('got output', saved);
-      console.timeEnd(name + '.TextEncoder');
-
-      console.time(name + '.TextDecoder');
-      const decoder = new tdec();
-      for (let i = 0; i < runs; ++i) {
-        const out = decoder.decode(saved);
-        output = out;
-      }
-      console.timeEnd(name + '.TextDecoder');
-    }
-
-    let saved, output;
-
-    console.time('utf8.encode');
-    for (let i = 0; i < runs; ++i) {
-      const s = utf8.encode(text);
-      saved = s;
-    }
-    console.timeEnd('utf8.encode');
-
-    console.time('utf8.decode');
-    for (let i = 0; i < runs; ++i) {
-      const out = utf8.decode(saved);
-      output = out;
-    }
-    console.timeEnd('utf8.decode');
-    if (output !== text) {
-      throw new Error('utf8 got wrong answer');
-    }
-
-
-    testEncodeDecode('native', TextEncoder, TextDecoder);
-    testEncodeDecode('fast', TextEncoderPolyfill, TextDecoderPolyfill);
-    testEncodeDecode('polyfill', polyfill.TextEncoder, polyfill.TextDecoder);
-
-  }());
-
-</script>
-</head>
-</html> -->
diff --git a/test.js b/test.js
new file mode 100644
index 0000000..08accfd
--- /dev/null
+++ b/test.js
@@ -0,0 +1,18 @@
+/**
+ * @fileoverview Test runner inside a Node environment.
+ */
+
+const mocha = require('mocha');
+const chai = require('chai');
+
+global.suite = mocha.suite;
+global.test = mocha.test;
+global.assert = chai.assert;
+
+global.NativeTextDecoder = global.TextDecoder;
+global.NativeTextEncoder = global.TextEncoder;
+global.TextDecoder = null;
+global.TextEncoder = null;
+
+require('./text.js');  // include polyfill
+require('./suite.js');
