diff --git a/package.json b/package.json
index 6022a2dcf..d14e7b7bc 100644
--- a/package.json
+++ b/package.json
@@ -77,6 +77,6 @@
     "compile": "NODE_ENV='production' webpack --config source/webpack.config.js",
     "surge": "npm run compile && surge --domain scientific-wish.surge.sh -p ./ && rm -rf dist/",
     "test": "mocha-webpack --webpack-config source/webpack.config.js --require source-map-support/register --require test/helpers/browser.js \"test/**/*.test.js\"",
-    "test-fast": "babel-node --presets babel-preset-flow,babel-preset-env --plugins transform-class-properties test/helpers/runner.js"
+    "test-fast": "babel-node --presets babel-preset-flow,babel-preset-env --plugins transform-class-properties test/helpers/runner.js -w"
   }
 }
diff --git a/test/helpers/runner.js b/test/helpers/runner.js
index ec3534ec9..129b04a38 100644
--- a/test/helpers/runner.js
+++ b/test/helpers/runner.js
@@ -1,8 +1,3 @@
-import Mocha from 'mocha';
-import chokidar from 'chokidar';
-
-const fs = require('fs');
-
 const noop = () => {}
 
 const loadYaml = (module, filename) =>  {
@@ -28,24 +23,542 @@ require.extensions['.yaml'] = loadYaml
 require.extensions['.ne'] = loadNearley
 require.extensions['.css'] = noop
 
-let fileList = [];
-function runSuite() {
-  Object.keys( require.cache ).forEach( key => delete require.cache[ key ] );
-  const mocha = new Mocha( { reporter: 'dot' } );
-  fileList.forEach( filepath => mocha.addFile( filepath ) );
-  mocha.run();
+/**
+ * Module dependencies.
+ */
+
+var program = require('commander');
+var path = require('path');
+var fs = require('fs');
+var resolve = path.resolve;
+var exists = fs.existsSync || path.existsSync;
+var Mocha = require('mocha');
+var utils = Mocha.utils;
+var interfaceNames = Object.keys(Mocha.interfaces);
+var join = path.join;
+var cwd = process.cwd();
+var getOptions = require('mocha/bin/options');
+var mocha = new Mocha();
+
+/**
+ * Save timer references to avoid Sinon interfering (see GH-237).
+ */
+
+var Date = global.Date;
+var setTimeout = global.setTimeout;
+var setInterval = global.setInterval;
+var clearTimeout = global.clearTimeout;
+var clearInterval = global.clearInterval;
+
+/**
+ * Files.
+ */
+
+var files = [];
+
+/**
+ * Globals.
+ */
+
+var globals = [];
+
+/**
+ * Requires.
+ */
+
+var requires = [];
+
+// options
+
+program
+  .usage('[debug] [options] [files]')
+  .option('-A, --async-only', 'force all tests to take a callback (async) or return a promise')
+  .option('-c, --colors', 'force enabling of colors')
+  .option('-C, --no-colors', 'force disabling of colors')
+  .option('-G, --growl', 'enable growl notification support')
+  .option('-O, --reporter-options <k=v,k2=v2,...>', 'reporter-specific options')
+  .option('-R, --reporter <name>', 'specify the reporter to use', 'spec')
+  .option('-S, --sort', 'sort test files')
+  .option('-b, --bail', 'bail after first test failure')
+  .option('-d, --debug', "enable node's debugger, synonym for node --debug")
+  .option('-g, --grep <pattern>', 'only run tests matching <pattern>')
+  .option('-f, --fgrep <string>', 'only run tests containing <string>')
+  .option('-gc, --expose-gc', 'expose gc extension')
+  .option('-i, --invert', 'inverts --grep and --fgrep matches')
+  .option('-r, --require <name>', 'require the given module')
+  .option('-s, --slow <ms>', '"slow" test threshold in milliseconds [75]')
+  .option('-t, --timeout <ms>', 'set test-case timeout in milliseconds [2000]')
+  .option('-u, --ui <name>', 'specify user-interface (' + interfaceNames.join('|') + ')', 'bdd')
+  .option('-w, --watch', 'watch files for changes')
+  .option('--check-leaks', 'check for global variable leaks')
+  .option('--full-trace', 'display the full stack trace')
+  .option('--compilers <ext>:<module>,...', 'use the given module(s) to compile files', list, [])
+  .option('--debug-brk', "enable node's debugger breaking on the first line")
+  .option('--globals <names>', 'allow the given comma-delimited global [names]', list, [])
+  .option('--es_staging', 'enable all staged features')
+  .option('--harmony<_classes,_generators,...>', 'all node --harmony* flags are available')
+  .option('--preserve-symlinks', 'Instructs the module loader to preserve symbolic links when resolving and caching modules')
+  .option('--icu-data-dir', 'include ICU data')
+  .option('--inline-diffs', 'display actual/expected differences inline within each string')
+  .option('--inspect', 'activate devtools in chrome')
+  .option('--inspect-brk', 'activate devtools in chrome and break on the first line')
+  .option('--interfaces', 'display available interfaces')
+  .option('--no-deprecation', 'silence deprecation warnings')
+  .option('--no-exit', 'require a clean shutdown of the event loop: mocha will not call process.exit')
+  .option('--no-timeouts', 'disables timeouts, given implicitly with --debug')
+  .option('--no-warnings', 'silence all node process warnings')
+  .option('--opts <path>', 'specify opts path', 'test/mocha.opts')
+  .option('--perf-basic-prof', 'enable perf linux profiler (basic support)')
+  .option('--napi-modules', 'enable experimental NAPI modules')
+  .option('--prof', 'log statistical profiling information')
+  .option('--log-timer-events', 'Time events including external callbacks')
+  .option('--recursive', 'include sub directories')
+  .option('--reporters', 'display available reporters')
+  .option('--retries <times>', 'set numbers of time to retry a failed test case')
+  .option('--throw-deprecation', 'throw an exception anytime a deprecated function is used')
+  .option('--trace', 'trace function calls')
+  .option('--trace-deprecation', 'show stack traces on deprecations')
+  .option('--trace-warnings', 'show stack traces on node process warnings')
+  .option('--use_strict', 'enforce strict mode')
+  .option('--watch-extensions <ext>,...', 'additional extensions to monitor with --watch', list, [])
+  .option('--delay', 'wait for async suite definition')
+  .option('--allow-uncaught', 'enable uncaught errors to propagate')
+  .option('--forbid-only', 'causes test marked with only to fail the suite')
+  .option('--forbid-pending', 'causes pending tests and test marked with skip to fail the suite');
+
+program._name = 'mocha';
+
+// --globals
+
+program.on('globals', function (val) {
+  globals = globals.concat(list(val));
+});
+
+// --reporters
+
+program.on('reporters', function () {
+  console.log();
+  console.log('    dot - dot matrix');
+  console.log('    doc - html documentation');
+  console.log('    spec - hierarchical spec list');
+  console.log('    json - single json object');
+  console.log('    progress - progress bar');
+  console.log('    list - spec-style listing');
+  console.log('    tap - test-anything-protocol');
+  console.log('    landing - unicode landing strip');
+  console.log('    xunit - xunit reporter');
+  console.log('    min - minimal reporter (great with --watch)');
+  console.log('    json-stream - newline delimited json events');
+  console.log('    markdown - markdown documentation (github flavour)');
+  console.log('    nyan - nyan cat!');
+  console.log();
+  process.exit();
+});
+
+// --interfaces
+
+program.on('interfaces', function () {
+  console.log('');
+  interfaceNames.forEach(function (interfaceName) {
+    console.log('    ' + interfaceName);
+  });
+  console.log('');
+  process.exit();
+});
+
+// -r, --require
+
+module.paths.push(cwd, join(cwd, 'node_modules'));
+
+program.on('require', function (mod) {
+  var abs = exists(mod) || exists(mod + '.js');
+  if (abs) {
+    mod = resolve(mod);
+  }
+  requires.push(mod);
+});
+
+// If not already done, load mocha.opts
+if (!process.env.LOADED_MOCHA_OPTS) {
+  getOptions();
+}
+
+// parse args
+
+program.parse(process.argv);
+
+// infinite stack traces
+
+Error.stackTraceLimit = Infinity; // TODO: config
+
+// reporter options
+
+var reporterOptions = {};
+if (program.reporterOptions !== undefined) {
+  program.reporterOptions.split(',').forEach(function (opt) {
+    var L = opt.split('=');
+    if (L.length > 2 || L.length === 0) {
+      throw new Error("invalid reporter option '" + opt + "'");
+    } else if (L.length === 2) {
+      reporterOptions[L[0]] = L[1];
+    } else {
+      reporterOptions[L[0]] = true;
+    }
+  });
+}
+
+// reporter
+
+mocha.reporter(program.reporter, reporterOptions);
+
+// load reporter
+
+var Reporter = null;
+try {
+  Reporter = require('mocha/lib/reporters/' + program.reporter);
+} catch (err) {
+  try {
+    Reporter = require(program.reporter);
+  } catch (err2) {
+    throw new Error('reporter "' + program.reporter + '" does not exist');
+  }
+}
+
+// --no-colors
+
+if (!program.colors) {
+  mocha.useColors(false);
+}
+
+// --colors
+
+if (~process.argv.indexOf('--colors') || ~process.argv.indexOf('-c')) {
+  mocha.useColors(true);
+}
+
+// --inline-diffs
+
+if (program.inlineDiffs) {
+  mocha.useInlineDiffs(true);
+}
+
+// --slow <ms>
+
+if (program.slow) {
+  mocha.suite.slow(program.slow);
+}
+
+// --no-timeouts
+
+if (!program.timeouts) {
+  mocha.enableTimeouts(false);
+}
+
+// --timeout
+
+if (program.timeout) {
+  mocha.suite.timeout(program.timeout);
+}
+
+// --bail
+
+mocha.suite.bail(program.bail);
+
+// --grep
+
+if (program.grep) {
+  mocha.grep(program.grep);
+}
+
+// --fgrep
+
+if (program.fgrep) {
+  mocha.fgrep(program.fgrep);
+}
+
+// --invert
+
+if (program.invert) {
+  mocha.invert();
+}
+
+// --check-leaks
+
+if (program.checkLeaks) {
+  mocha.checkLeaks();
+}
+
+// --stack-trace
+
+if (program.fullTrace) {
+  mocha.fullTrace();
+}
+
+// --growl
+
+if (program.growl) {
+  mocha.growl();
+}
+
+// --async-only
+
+if (program.asyncOnly) {
+  mocha.asyncOnly();
+}
+
+// --delay
+
+if (program.delay) {
+  mocha.delay();
+}
+
+// --allow-uncaught
+
+if (program.allowUncaught) {
+  mocha.allowUncaught();
+}
+
+// --globals
+
+mocha.globals(globals);
+
+// --retries
+
+if (program.retries) {
+  mocha.suite.retries(program.retries);
+}
+
+// --forbid-only
+
+if (program.forbidOnly) mocha.forbidOnly();
+
+// --forbid-pending
+
+if (program.forbidPending) mocha.forbidPending();
+
+// custom compiler support
+
+var extensions = ['js'];
+program.compilers.forEach(function (c) {
+  var idx = c.indexOf(':');
+  var ext = c.slice(0, idx);
+  var mod = c.slice(idx + 1);
+
+  if (mod[0] === '.') {
+    mod = join(process.cwd(), mod);
+  }
+  require(mod);
+  extensions.push(ext);
+  program.watchExtensions.push(ext);
+});
+
+// requires
+
+requires.forEach(function (mod) {
+  require(mod);
+});
+
+// interface
+
+mocha.ui(program.ui);
+
+// args
+
+var args = program.args;
+
+// default files to test/*.{js,coffee}
+
+if (!args.length) {
+  args.push('test');
+}
+
+args.forEach(function (arg) {
+  var newFiles;
+  try {
+    newFiles = utils.lookupFiles(arg, extensions, program.recursive);
+  } catch (err) {
+    if (err.message.indexOf('cannot resolve path') === 0) {
+      console.error('Warning: Could not find any test files matching pattern: ' + arg);
+      return;
+    }
+
+    throw err;
+  }
+
+  files = files.concat(newFiles);
+});
+
+if (!files.length) {
+  console.error('No test files found');
+  process.exit(1);
+}
+
+// resolve
+
+files = files.map(function (path) {
+  return resolve(path);
+});
+
+if (program.sort) {
+  files.sort();
+}
+
+// --watch
+
+var runner;
+var loadAndRun;
+var purge;
+var rerun;
+
+if (program.watch) {
+  console.log();
+  hideCursor();
+  process.on('SIGINT', function () {
+    showCursor();
+    console.log('\n');
+    process.exit(130);
+  });
+
+  var watchFiles = utils.files(cwd, [ 'js' ].concat(program.watchExtensions));
+  var runAgain = false;
+
+  loadAndRun = function loadAndRun () {
+    try {
+      mocha.files = files;
+      runAgain = false;
+      runner = mocha.run(function () {
+        runner = null;
+        if (runAgain) {
+          rerun();
+        }
+      });
+    } catch (e) {
+      console.log(e.stack);
+    }
+  };
+
+  purge = function purge () {
+    watchFiles.forEach(function (file) {
+      delete require.cache[file];
+    });
+  };
+
+  loadAndRun();
+
+  rerun = function rerun () {
+    purge();
+    stop();
+    if (!program.grep) {
+      mocha.grep(null);
+    }
+    mocha.suite = mocha.suite.clone();
+    mocha.suite.ctx = new Mocha.Context();
+    mocha.ui(program.ui);
+    loadAndRun();
+  };
+
+  utils.watch(watchFiles, function () {
+    runAgain = true;
+    if (runner) {
+      runner.abort();
+    } else {
+      rerun();
+    }
+  });
+} else {
+// load
+
+  mocha.files = files;
+  runner = mocha.run(program.exit ? exit : exitLater);
+}
+
+function exitLater (code) {
+  process.on('exit', function () {
+    process.exit(Math.min(code, 255));
+  });
+}
+
+function exit (code) {
+  var clampedCode = Math.min(code, 255);
+
+  // Eagerly set the process's exit code in case stream.write doesn't
+  // execute its callback before the process terminates.
+  process.exitCode = clampedCode;
+
+  // flush output for Node.js Windows pipe bug
+  // https://github.com/joyent/node/issues/6247 is just one bug example
+  // https://github.com/visionmedia/mocha/issues/333 has a good discussion
+  function done () {
+    if (!(draining--)) {
+      process.exit(clampedCode);
+    }
+  }
+
+  var draining = 0;
+  var streams = [process.stdout, process.stderr];
+
+  streams.forEach(function (stream) {
+    // submit empty write request and wait for completion
+    draining += 1;
+    stream.write('', done);
+  });
+
+  done();
+}
+
+process.on('SIGINT', function () {
+  runner.abort();
+
+  // This is a hack:
+  // Instead of `process.exit(130)`, set runner.failures to 130 (exit code for SIGINT)
+  // The amount of failures will be emitted as error code later
+  runner.failures = 130;
+});
+
+/**
+ * Parse list.
+ */
+
+function list (str) {
+  return str.split(/ *, */);
 }
 
 /**
- * Chokidar watches all the files for any kind of change and calls the run function
- * from above. Read more: https://github.com/paulmillr/chokidar
- * @param  {string} a glob of files to watch
- * @param  {object} settings
+ * Hide the cursor.
  */
-chokidar.watch( 'test/**/*.test.js', { persistent: true } )
-  .on( 'add', path => fileList.push( path ) )
-  .on( 'change', path => runSuite() )
-  .on( 'ready', () => runSuite() );
 
-chokidar.watch( 'source/**/*.js', { persistent: true } )
-  .on( 'change', path => runSuite() )
+function hideCursor () {
+  process.stdout.write('\u001b[?25l');
+}
+
+/**
+ * Show the cursor.
+ */
+
+function showCursor () {
+  process.stdout.write('\u001b[?25h');
+}
+
+/**
+ * Stop play()ing.
+ */
+
+function stop () {
+  process.stdout.write('\u001b[2K');
+  clearInterval(play.timer);
+}
+
+/**
+ * Play the given array of strings.
+ */
+
+function play (arr, interval) {
+  var len = arr.length;
+  interval = interval || 100;
+  var i = 0;
+
+  play.timer = setInterval(function () {
+    var str = arr[i++ % len];
+    process.stdout.write('\u001b[0G' + str);
+  }, interval);
+}
diff --git a/test/mocha.opts b/test/mocha.opts
index 4092fbfd4..880f37f14 100644
--- a/test/mocha.opts
+++ b/test/mocha.opts
@@ -1,2 +1,2 @@
---compilers js:babel-register
 test/**/*.test.js
+