diff --git a/karma.conf.js b/karma.conf.js
index fcdf9beb..3a3ef675 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -1,10 +1,15 @@
+// Karma configuration
+// https://karma-runner.github.io/5.2/config/configuration-file.html
 module.exports = config => {
   config.set({
+    // base path that will be used to resolve all patterns (eg. files, exclude)
+    basePath: '',
+
+    // frameworks to use
+    // available frameworks: https://npmjs.org/browse/keyword/karma-adapter
     frameworks: ['mocha', 'chai', 'commonjs'],
-    reporters: ['mocha'],
-    mochaReporter: {
-      showDiff: true
-    },
+
+    // list of files / patterns to load in the browser
     files: [
       'dist/htmlparser2.js',
       'lib/*.js',
@@ -12,12 +17,70 @@ module.exports = config => {
       'test/client/*.js',
       'test/helpers/*.js'
     ],
+
+    // list of files / patterns to exclude
     exclude: ['lib/html-to-dom-server.js'],
-    browsers: ['Chrome'],
+
+    // preprocess matching files before serving them to the browser
+    // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
     preprocessors: {
       'dist/**/*.js': ['commonjs'],
       'lib/**/*.js': ['commonjs'],
       'test/**/*.js': ['commonjs']
+    },
+
+    // test results reporter to use
+    // possible values: 'dots', 'progress'
+    // available reporters: https://npmjs.org/browse/keyword/karma-reporter
+    reporters: ['mocha', 'progress'],
+
+    // web server port
+    port: 9876,
+
+    // enable / disable colors in the output (reporters and logs)
+    colors: true,
+
+    // level of logging
+    // possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
+    logLevel: config.LOG_INFO,
+
+    // enable / disable watching file and executing tests whenever any file changes
+    autoWatch: true,
+
+    // Start these browsers, currently available:
+    // - Chrome
+    // - ChromeCanary
+    // - Firefox
+    // - Opera (has to be installed with `npm install karma-opera-launcher`)
+    // - Safari (only Mac; has to be installed with `npm install karma-safari-launcher`)
+    // - PhantomJS
+    // - IE (only Windows; has to be installed with `npm install karma-ie-launcher`)
+    // available browser launchers: https://npmjs.org/browse/keyword/karma-launcher
+    browsers: ['Chrome'],
+
+    // If browser does not capture in given timeout [ms], kill it
+    captureTimeout: 60000,
+
+    // Continuous Integration mode
+    // if true, Karma captures browsers, runs the tests and exits
+    singleRun: false,
+
+    // Concurrency level
+    // how many browser should be started simultaneous
+    concurrency: Infinity,
+
+    // Client options
+    client: {
+      mocha: {
+        // change Karma's `debug.html` to the Mocha web reporter
+        reporter: 'html'
+      }
+    },
+
+    // Mocha reporter options
+    // https://www.npmjs.com/package/karma-mocha-reporter
+    mochaReporter: {
+      showDiff: true
     }
   });
 };
diff --git a/test/client/index.js b/test/client/index.js
index 15a049a7..7d507951 100644
--- a/test/client/index.js
+++ b/test/client/index.js
@@ -1,21 +1,23 @@
 var assert = window.chai.assert;
 var htmlCases = require('../cases/html');
-var htmlparser = require('../../dist/htmlparser2');
-var parser = require('../../lib/html-to-dom-client');
+var serverParser = require('../../dist/htmlparser2').parseDOM;
+var clientParser = require('../../lib/html-to-dom-client');
 var helpers = require('../helpers');
 
 describe('client parser', function () {
-  helpers.throwsError(parser, assert);
-  helpers.runTests(htmlCases, parser, htmlparser.parseDOM, assert);
+  helpers.throwsError(clientParser, assert);
+  helpers.runTests(htmlCases, clientParser, serverParser, assert);
 
-  it.skip('performance', function () {
-    var html = '<div>test</div>';
-    var start = performance.now();
-    var times = 1000;
-    while (--times) {
-      parser(html);
-    }
-    var end = performance.now();
-    console.log('performance: ' + (end - start) + ' milliseconds'); // eslint-disable-line no-console
+  describe('performance', function () {
+    it('executes 1000 times in less than 50ms', function () {
+      var times = 1000;
+      var start = performance.now();
+      while (--times) {
+        clientParser('<div>test</div>');
+      }
+      var end = performance.now();
+      var elapsed = end - start;
+      assert.isBelow(elapsed, 50);
+    });
   });
 });
diff --git a/test/helpers/run-tests.js b/test/helpers/run-tests.js
index 8e1f4bb8..24bff338 100644
--- a/test/helpers/run-tests.js
+++ b/test/helpers/run-tests.js
@@ -1,17 +1,12 @@
 /**
  * Runs tests.
  *
- * @param {Object}   testCases      - The test cases.
- * @param {Function} expectedParser - The expected parser.
- * @param {Function} actualParser   - The actual parser.
- * @param {Function} [assert]       - The assertion module.
+ * @param {Object}   testCases      - Test cases.
+ * @param {Function} expectedParser - Expected parser.
+ * @param {Function} actualParser   - Actual parser.
+ * @param {Function} [assert]       - Assertion module.
  */
-module.exports = function runTests(
-  testCases,
-  expectedParser,
-  actualParser,
-  assert
-) {
+function runTests(testCases, expectedParser, actualParser, assert) {
   if (typeof assert !== 'function') {
     assert = require('assert');
   }
@@ -24,16 +19,20 @@ module.exports = function runTests(
     throw new TypeError('Missing or invalid actual parser');
   }
 
+  // enable `decodeEntities` for both parsers
+  // because entities are decoded on the browser
+  var parserOptions = { decodeEntities: true };
+
   testCases.forEach(function (testCase) {
     var _it = testCase.only ? it.only : testCase.skip ? it.skip : it;
 
     _it('parses ' + testCase.name, function () {
-      // enable decodeEntities for both parsers because
-      // entities are decoded by client parser in jsdom
       assert.deepEqual(
-        expectedParser(testCase.data, { decodeEntities: true }),
-        actualParser(testCase.data, { decodeEntities: true })
+        actualParser(testCase.data, parserOptions),
+        expectedParser(testCase.data, parserOptions)
       );
     });
   });
-};
+}
+
+module.exports = runTests;