diff --git a/Errors.js b/Errors.js
new file mode 100644
index 00000000..dc41298a
--- /dev/null
+++ b/Errors.js
@@ -0,0 +1,28 @@
+/**
+ * Copyright 2018 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+let asyncawait = true;
+try {
+  new Function('async function test(){await 1}');
+} catch (error) {
+  asyncawait = false;
+}
+
+// If node does not support async await, use the compiled version.
+if (asyncawait)
+  module.exports = require('./lib/Errors');
+else
+  module.exports = require('./node6/lib/Errors');
diff --git a/docs/api.md b/docs/api.md
index a391df72..5af18695 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -12,6 +12,7 @@ Next Release: **Aug 9, 2018**
 <!-- GEN:toc -->
 - [Overview](#overview)
 - [Environment Variables](#environment-variables)
+- [Error handling](#error-handling)
 - [Working with Chrome Extensions](#working-with-chrome-extensions)
 - [class: Puppeteer](#class-puppeteer)
   * [puppeteer.connect(options)](#puppeteerconnectoptions)
@@ -285,6 +286,7 @@ Next Release: **Aug 9, 2018**
   * [coverage.startJSCoverage(options)](#coveragestartjscoverageoptions)
   * [coverage.stopCSSCoverage()](#coveragestopcsscoverage)
   * [coverage.stopJSCoverage()](#coveragestopjscoverage)
+- [class: TimeoutError](#class-timeouterror)
 <!-- GEN:stop -->
 
 ### Overview
@@ -316,6 +318,34 @@ If puppeteer doesn't find them in environment, lowercased variant of these varia
 - `PUPPETEER_DOWNLOAD_HOST` - overwrite host part of URL that is used to download Chromium
 - `PUPPETEER_CHROMIUM_REVISION` - specify a certain version of chrome you'd like puppeteer to use during the installation step.
 
+### Error handling
+
+Often times, async methods might throw an error, signaling about their inability
+to fulfill request. For example, [page.waitForSelector(selector[, options])](#pagewaitforselectorselector-options)
+might fail if selector doesn't appear during the given timeframe.
+
+For certain types of errors Puppeteer uses specific error classes.
+These classes are available through the `require('puppeteer/Errors')`.
+
+List of supported classes:
+- [`TimeoutError`](#class-timeouterror)
+
+An example of handling timeout error:
+```js
+const {TimeoutError} = require('puppeteer/Errors');
+
+// ...
+
+try {
+  await page.waitForSelector('.foo');
+} catch (e) {
+  if (e instanceof TimeoutError) {
+    // Do something if this is a timeout.
+  }
+}
+```
+
+
 ### Working with Chrome Extensions
 
 Puppeteer can be used for testing Chrome Extensions.
@@ -3157,6 +3187,14 @@ _To output coverage in a form consumable by [Istanbul](https://github.com/istanb
 > **NOTE** JavaScript Coverage doesn't include anonymous scripts by default. However, scripts with sourceURLs are
 reported.
 
+### class: TimeoutError
+
+* extends: [Error]
+
+TimeoutError is emitted whenever certain operations are terminated due to timeout, e.g. [page.waitForSelector(selector[, options])](#pagewaitforselectorselector-options) or [puppeteer.launch([options])](#puppeteerlaunchoptions).
+
+
+
 [Array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array "Array"
 [boolean]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type "Boolean"
 [Buffer]: https://nodejs.org/api/buffer.html#buffer_class_buffer "Buffer"
diff --git a/lib/BrowserFetcher.js b/lib/BrowserFetcher.js
index a550cfc5..0c8f761c 100644
--- a/lib/BrowserFetcher.js
+++ b/lib/BrowserFetcher.js
@@ -156,7 +156,7 @@ class BrowserFetcher {
     else if (this._platform === 'win32' || this._platform === 'win64')
       executablePath = path.join(folderPath, 'chrome-win32', 'chrome.exe');
     else
-      throw 'Unsupported platform: ' + this._platform;
+      throw new Error('Unsupported platform: ' + this._platform);
     let url = downloadURLs[this._platform];
     url = util.format(url, this._downloadHost, revision);
     const local = fs.existsSync(folderPath);
diff --git a/lib/Errors.js b/lib/Errors.js
new file mode 100644
index 00000000..1bcfc2d0
--- /dev/null
+++ b/lib/Errors.js
@@ -0,0 +1,29 @@
+/**
+ * Copyright 2018 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+class CustomError extends Error {
+  constructor(message) {
+    super(message);
+    this.name = this.constructor.name;
+    Error.captureStackTrace(this, this.constructor);
+  }
+}
+
+class TimeoutError extends CustomError {}
+
+module.exports = {
+  TimeoutError,
+};
diff --git a/lib/FrameManager.js b/lib/FrameManager.js
index 8e1f2381..963a1e3b 100644
--- a/lib/FrameManager.js
+++ b/lib/FrameManager.js
@@ -19,6 +19,7 @@ const EventEmitter = require('events');
 const {helper, assert} = require('./helper');
 const {ExecutionContext, JSHandle} = require('./ExecutionContext');
 const {ElementHandle} = require('./ElementHandle');
+const {TimeoutError} = require('./Errors');
 
 const readFileAsync = helper.promisify(fs.readFile);
 
@@ -876,7 +877,7 @@ class WaitTask {
     // Since page navigation requires us to re-install the pageScript, we should track
     // timeout on our end.
     if (timeout) {
-      const timeoutError = new Error(`waiting for ${title} failed: timeout ${timeout}ms exceeded`);
+      const timeoutError = new TimeoutError(`waiting for ${title} failed: timeout ${timeout}ms exceeded`);
       this._timeoutTimer = setTimeout(() => this.terminate(timeoutError), timeout);
     }
     this.rerun();
diff --git a/lib/Launcher.js b/lib/Launcher.js
index 4c58f1e9..b735c017 100644
--- a/lib/Launcher.js
+++ b/lib/Launcher.js
@@ -24,6 +24,7 @@ const readline = require('readline');
 const fs = require('fs');
 const {helper, assert, debugError} = require('./helper');
 const ChromiumRevision = require(path.join(helper.projectRoot(), 'package.json')).puppeteer.chromium_revision;
+const {TimeoutError} = require('./Errors');
 
 const mkdtempAsync = helper.promisify(fs.mkdtemp);
 const removeFolderAsync = helper.promisify(removeFolder);
@@ -306,7 +307,7 @@ function waitForWSEndpoint(chromeProcess, timeout) {
 
     function onTimeout() {
       cleanup();
-      reject(new Error(`Timed out after ${timeout} ms while trying to connect to Chrome! The only Chrome revision guaranteed to work is r${ChromiumRevision}`));
+      reject(new TimeoutError(`Timed out after ${timeout} ms while trying to connect to Chrome! The only Chrome revision guaranteed to work is r${ChromiumRevision}`));
     }
 
     /**
diff --git a/lib/NavigatorWatcher.js b/lib/NavigatorWatcher.js
index abdbd99d..e909b5be 100644
--- a/lib/NavigatorWatcher.js
+++ b/lib/NavigatorWatcher.js
@@ -16,6 +16,7 @@
 
 const {helper, assert} = require('./helper');
 const {FrameManager} = require('./FrameManager');
+const {TimeoutError} = require('./Errors');
 
 class NavigatorWatcher {
   /**
@@ -70,7 +71,7 @@ class NavigatorWatcher {
       return new Promise(() => {});
     const errorMessage = 'Navigation Timeout Exceeded: ' + this._timeout + 'ms exceeded';
     return new Promise(fulfill => this._maximumTimer = setTimeout(fulfill, this._timeout))
-        .then(() => new Error(errorMessage));
+        .then(() => new TimeoutError(errorMessage));
   }
 
   /**
diff --git a/lib/helper.js b/lib/helper.js
index 5770f056..f5dbf0e3 100644
--- a/lib/helper.js
+++ b/lib/helper.js
@@ -15,6 +15,7 @@
  */
 const fs = require('fs');
 const path = require('path');
+const {TimeoutError} = require('./Errors');
 
 const debugError = require('debug')(`puppeteer:error`);
 /** @type {?Map<string, boolean>} */
@@ -262,7 +263,7 @@ class Helper {
     if (timeout) {
       eventTimeout = setTimeout(() => {
         cleanup();
-        rejectCallback(new Error('Timeout exceeded while waiting for event'));
+        rejectCallback(new TimeoutError('Timeout exceeded while waiting for event'));
       }, timeout);
     }
     function cleanup() {
diff --git a/test/browser.spec.js b/test/browser.spec.js
index 384eb173..bceabc32 100644
--- a/test/browser.spec.js
+++ b/test/browser.spec.js
@@ -13,8 +13,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+const utils = require('./utils');
+const puppeteer = utils.requireRoot('index');
 
-module.exports.addTests = function({testRunner, expect, puppeteer, headless}) {
+module.exports.addTests = function({testRunner, expect, headless}) {
   const {describe, xdescribe, fdescribe} = testRunner;
   const {it, fit, xit} = testRunner;
   const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
diff --git a/test/browsercontext.spec.js b/test/browsercontext.spec.js
index a2a317b5..e207e931 100644
--- a/test/browsercontext.spec.js
+++ b/test/browsercontext.spec.js
@@ -15,8 +15,9 @@
  */
 
 const utils = require('./utils');
+const puppeteer = utils.requireRoot('index');
 
-module.exports.addTests = function({testRunner, expect, puppeteer}) {
+module.exports.addTests = function({testRunner, expect}) {
   const {describe, xdescribe, fdescribe} = testRunner;
   const {it, fit, xit} = testRunner;
   const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
diff --git a/test/frame.spec.js b/test/frame.spec.js
index 46d925d5..db4621ba 100644
--- a/test/frame.spec.js
+++ b/test/frame.spec.js
@@ -15,6 +15,7 @@
  */
 
 const utils = require('./utils');
+const {TimeoutError} = utils.requireRoot('Errors');
 
 module.exports.addTests = function({testRunner, expect}) {
   const {describe, xdescribe, fdescribe} = testRunner;
@@ -165,6 +166,7 @@ module.exports.addTests = function({testRunner, expect}) {
       await page.waitForFunction('false', {timeout: 10}).catch(e => error = e);
       expect(error).toBeTruthy();
       expect(error.message).toContain('waiting for function failed: timeout');
+      expect(error).toBeInstanceOf(TimeoutError);
     });
     it('should disable timeout when its set to 0', async({page}) => {
       const watchdog = page.waitForFunction(() => {
@@ -317,6 +319,7 @@ module.exports.addTests = function({testRunner, expect}) {
       await page.waitForSelector('div', {timeout: 10}).catch(e => error = e);
       expect(error).toBeTruthy();
       expect(error.message).toContain('waiting for selector "div" failed: timeout');
+      expect(error).toBeInstanceOf(TimeoutError);
     });
     it('should have an error message specifically for awaiting an element to be hidden', async({page, server}) => {
       await page.setContent(`<div></div>`);
@@ -359,6 +362,7 @@ module.exports.addTests = function({testRunner, expect}) {
       await page.waitForXPath('//div', {timeout: 10}).catch(e => error = e);
       expect(error).toBeTruthy();
       expect(error.message).toContain('waiting for XPath "//div" failed: timeout');
+      expect(error).toBeInstanceOf(TimeoutError);
     });
     it('should run in specified frame', async({page, server}) => {
       await utils.attachFrame(page, 'frame1', server.EMPTY_PAGE);
diff --git a/test/headful.spec.js b/test/headful.spec.js
index bd3ad8f8..972f38f4 100644
--- a/test/headful.spec.js
+++ b/test/headful.spec.js
@@ -16,7 +16,9 @@
 
 const path = require('path');
 const os = require('os');
-const {waitEvent} = require('./utils.js');
+const utils = require('./utils');
+const {waitEvent} = utils;
+const puppeteer = utils.requireRoot('index.js');
 
 const TMP_FOLDER = path.join(os.tmpdir(), 'pptr_tmp_folder-');
 
@@ -34,11 +36,10 @@ function waitForBackgroundPageTarget(browser) {
   });
 }
 
-module.exports.addTests = function({testRunner, expect, PROJECT_ROOT, defaultBrowserOptions}) {
+module.exports.addTests = function({testRunner, expect, defaultBrowserOptions}) {
   const {describe, xdescribe, fdescribe} = testRunner;
   const {it, fit, xit} = testRunner;
   const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
-  const puppeteer = require(PROJECT_ROOT);
 
   const headfulOptions = Object.assign({}, defaultBrowserOptions, {
     headless: false
diff --git a/test/ignorehttpserrors.spec.js b/test/ignorehttpserrors.spec.js
index ec5b0c67..17d21d37 100644
--- a/test/ignorehttpserrors.spec.js
+++ b/test/ignorehttpserrors.spec.js
@@ -14,11 +14,13 @@
  * limitations under the License.
  */
 
-module.exports.addTests = function({testRunner, expect, PROJECT_ROOT, defaultBrowserOptions}) {
+const utils = require('./utils');
+const puppeteer = utils.requireRoot('index.js');
+
+module.exports.addTests = function({testRunner, expect, defaultBrowserOptions}) {
   const {describe, xdescribe, fdescribe} = testRunner;
   const {it, fit, xit} = testRunner;
   const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
-  const puppeteer = require(PROJECT_ROOT);
   describe('ignoreHTTPSErrors', function() {
     beforeAll(async state => {
       const options = Object.assign({ignoreHTTPSErrors: true}, defaultBrowserOptions);
diff --git a/test/input.spec.js b/test/input.spec.js
index 9505b06c..5a583e00 100644
--- a/test/input.spec.js
+++ b/test/input.spec.js
@@ -16,12 +16,13 @@
 
 const path = require('path');
 const utils = require('./utils');
+const DeviceDescriptors = utils.requireRoot('DeviceDescriptors');
+const iPhone = DeviceDescriptors['iPhone 6'];
 
-module.exports.addTests = function({testRunner, expect, DeviceDescriptors}) {
+module.exports.addTests = function({testRunner, expect}) {
   const {describe, xdescribe, fdescribe} = testRunner;
   const {it, fit, xit} = testRunner;
   const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
-  const iPhone = DeviceDescriptors['iPhone 6'];
   describe('input', function() {
     it('should click the button', async({page, server}) => {
       await page.goto(server.PREFIX + '/input/button.html');
diff --git a/test/page.spec.js b/test/page.spec.js
index ee80272a..a966fc99 100644
--- a/test/page.spec.js
+++ b/test/page.spec.js
@@ -16,14 +16,17 @@
 const fs = require('fs');
 const path = require('path');
 const utils = require('./utils');
-const {waitEvent} = require('./utils');
+const {waitEvent} = utils;
+const {TimeoutError} = utils.requireRoot('Errors');
 
-module.exports.addTests = function({testRunner, expect, puppeteer, DeviceDescriptors, headless}) {
+const DeviceDescriptors = utils.requireRoot('DeviceDescriptors');
+const iPhone = DeviceDescriptors['iPhone 6'];
+const iPhoneLandscape = DeviceDescriptors['iPhone 6 landscape'];
+
+module.exports.addTests = function({testRunner, expect, headless}) {
   const {describe, xdescribe, fdescribe} = testRunner;
   const {it, fit, xit} = testRunner;
   const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
-  const iPhone = DeviceDescriptors['iPhone 6'];
-  const iPhoneLandscape = DeviceDescriptors['iPhone 6 landscape'];
 
   describe('Page.close', function() {
     it('should reject all promises when page is closed', async({context}) => {
@@ -531,6 +534,7 @@ module.exports.addTests = function({testRunner, expect, puppeteer, DeviceDescrip
       let error = null;
       await page.goto(server.PREFIX + '/empty.html', {timeout: 1}).catch(e => error = e);
       expect(error.message).toContain('Navigation Timeout Exceeded: 1ms');
+      expect(error).toBeInstanceOf(TimeoutError);
     });
     it('should fail when exceeding default maximum navigation timeout', async({page, server}) => {
       // Hang for request to the empty.html
@@ -539,6 +543,7 @@ module.exports.addTests = function({testRunner, expect, puppeteer, DeviceDescrip
       page.setDefaultNavigationTimeout(1);
       await page.goto(server.PREFIX + '/empty.html').catch(e => error = e);
       expect(error.message).toContain('Navigation Timeout Exceeded: 1ms');
+      expect(error).toBeInstanceOf(TimeoutError);
     });
     it('should disable timeout when its set to 0', async({page, server}) => {
       let error = null;
diff --git a/test/puppeteer.spec.js b/test/puppeteer.spec.js
index d45fab9d..032e9197 100644
--- a/test/puppeteer.spec.js
+++ b/test/puppeteer.spec.js
@@ -23,12 +23,12 @@ const readFileAsync = helper.promisify(fs.readFile);
 const statAsync = helper.promisify(fs.stat);
 const TMP_FOLDER = path.join(os.tmpdir(), 'pptr_tmp_folder-');
 const utils = require('./utils');
+const puppeteer = utils.requireRoot('index');
 
-module.exports.addTests = function({testRunner, expect, PROJECT_ROOT, defaultBrowserOptions}) {
+module.exports.addTests = function({testRunner, expect, defaultBrowserOptions}) {
   const {describe, xdescribe, fdescribe} = testRunner;
   const {it, fit, xit} = testRunner;
   const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
-  const puppeteer = require(PROJECT_ROOT);
 
   describe('Puppeteer', function() {
     describe('BrowserFetcher', function() {
@@ -145,7 +145,7 @@ module.exports.addTests = function({testRunner, expect, PROJECT_ROOT, defaultBro
         const {spawn} = require('child_process');
         const options = Object.assign({}, defaultBrowserOptions, {dumpio: true});
         const res = spawn('node',
-            [path.join(__dirname, 'fixtures', 'dumpio.js'), PROJECT_ROOT, JSON.stringify(options), server.EMPTY_PAGE, dumpioTextToLog]);
+            [path.join(__dirname, 'fixtures', 'dumpio.js'), utils.projectRoot(), JSON.stringify(options), server.EMPTY_PAGE, dumpioTextToLog]);
         res.stderr.on('data', data => dumpioData += data.toString('utf8'));
         await new Promise(resolve => res.on('close', resolve));
 
@@ -153,7 +153,7 @@ module.exports.addTests = function({testRunner, expect, PROJECT_ROOT, defaultBro
       });
       it('should close the browser when the node process closes', async({ server }) => {
         const {spawn, execSync} = require('child_process');
-        const res = spawn('node', [path.join(__dirname, 'fixtures', 'closeme.js'), PROJECT_ROOT, JSON.stringify(defaultBrowserOptions)]);
+        const res = spawn('node', [path.join(__dirname, 'fixtures', 'closeme.js'), utils.projectRoot(), JSON.stringify(defaultBrowserOptions)]);
         let wsEndPointCallback;
         const wsEndPointPromise = new Promise(x => wsEndPointCallback = x);
         let output = '';
diff --git a/test/target.spec.js b/test/target.spec.js
index ca1bbb66..1fcb0721 100644
--- a/test/target.spec.js
+++ b/test/target.spec.js
@@ -14,9 +14,10 @@
  * limitations under the License.
  */
 
-const {waitEvent} = require('./utils');
+const utils = require('./utils');
+const {waitEvent} = utils;
 
-module.exports.addTests = function({testRunner, expect, puppeteer}) {
+module.exports.addTests = function({testRunner, expect}) {
   const {describe, xdescribe, fdescribe} = testRunner;
   const {it, fit, xit} = testRunner;
   const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
diff --git a/test/test.js b/test/test.js
index fd95f6eb..79afd73e 100644
--- a/test/test.js
+++ b/test/test.js
@@ -21,14 +21,13 @@ const GoldenUtils = require('./golden-utils');
 const GOLDEN_DIR = path.join(__dirname, 'golden');
 const OUTPUT_DIR = path.join(__dirname, 'output');
 const {TestRunner, Reporter, Matchers} = require('../utils/testrunner/');
+const utils = require('./utils');
 
 const {helper, assert} = require('../lib/helper');
 if (process.env.COVERAGE)
   helper.recordPublicAPICoverage();
 
-const PROJECT_ROOT = fs.existsSync(path.join(__dirname, '..', 'package.json')) ? path.join(__dirname, '..') : path.join(__dirname, '..', '..');
-const puppeteer = require(PROJECT_ROOT);
-const DeviceDescriptors = require(path.join(PROJECT_ROOT, 'DeviceDescriptors'));
+const puppeteer = utils.requireRoot('index');
 
 const YELLOW_COLOR = '\x1b[33m';
 const RESET_COLOR = '\x1b[0m';
@@ -145,28 +144,28 @@ describe('Browser', function() {
     // Page-level tests that are given a browser, a context and a page.
     // Each test is launched in a new browser context.
     require('./CDPSession.spec.js').addTests({testRunner, expect});
-    require('./browser.spec.js').addTests({testRunner, expect, puppeteer, headless});
+    require('./browser.spec.js').addTests({testRunner, expect, headless});
     require('./cookies.spec.js').addTests({testRunner, expect});
     require('./coverage.spec.js').addTests({testRunner, expect});
     require('./elementhandle.spec.js').addTests({testRunner, expect});
     require('./frame.spec.js').addTests({testRunner, expect});
-    require('./input.spec.js').addTests({testRunner, expect, DeviceDescriptors});
+    require('./input.spec.js').addTests({testRunner, expect});
     require('./jshandle.spec.js').addTests({testRunner, expect});
     require('./network.spec.js').addTests({testRunner, expect});
-    require('./page.spec.js').addTests({testRunner, expect, puppeteer, DeviceDescriptors, headless});
-    require('./target.spec.js').addTests({testRunner, expect, puppeteer});
+    require('./page.spec.js').addTests({testRunner, expect, headless});
+    require('./target.spec.js').addTests({testRunner, expect});
     require('./tracing.spec.js').addTests({testRunner, expect});
     require('./worker.spec.js').addTests({testRunner, expect});
   });
 
   // Browser-level tests that are given a browser.
-  require('./browsercontext.spec.js').addTests({testRunner, expect, puppeteer});
+  require('./browsercontext.spec.js').addTests({testRunner, expect});
 });
 
 // Top-level tests that launch Browser themselves.
-require('./ignorehttpserrors.spec.js').addTests({testRunner, expect, PROJECT_ROOT, defaultBrowserOptions});
-require('./puppeteer.spec.js').addTests({testRunner, expect, PROJECT_ROOT, defaultBrowserOptions});
-require('./headful.spec.js').addTests({testRunner, expect, PROJECT_ROOT, defaultBrowserOptions});
+require('./ignorehttpserrors.spec.js').addTests({testRunner, expect, defaultBrowserOptions});
+require('./puppeteer.spec.js').addTests({testRunner, expect, defaultBrowserOptions});
+require('./headful.spec.js').addTests({testRunner, expect, defaultBrowserOptions});
 
 if (process.env.COVERAGE) {
   describe('COVERAGE', function() {
diff --git a/test/utils.js b/test/utils.js
index 3aae5f8d..a8e7e805 100644
--- a/test/utils.js
+++ b/test/utils.js
@@ -14,7 +14,25 @@
  * limitations under the License.
  */
 
+const fs = require('fs');
+const path = require('path');
+const PROJECT_ROOT = fs.existsSync(path.join(__dirname, '..', 'package.json')) ? path.join(__dirname, '..') : path.join(__dirname, '..', '..');
+
 const utils = module.exports = {
+  /**
+   * @return {string}
+   */
+  projectRoot: function() {
+    return PROJECT_ROOT;
+  },
+
+  /**
+   * @return {*}
+   */
+  requireRoot: function(name) {
+    return require(path.join(PROJECT_ROOT, name));
+  },
+
   /**
    * @param {!Page} page
    * @param {string} frameId
diff --git a/utils/doclint/check_public_api/index.js b/utils/doclint/check_public_api/index.js
index b3a97b0a..d6b255dc 100644
--- a/utils/doclint/check_public_api/index.js
+++ b/utils/doclint/check_public_api/index.js
@@ -22,6 +22,7 @@ const Message = require('../Message');
 const EXCLUDE_CLASSES = new Set([
   'CSSCoverage',
   'Connection',
+  'CustomError',
   'EmulationManager',
   'FrameManager',
   'JSCoverage',
@@ -35,11 +36,12 @@ const EXCLUDE_CLASSES = new Set([
   'WaitTask',
 ]);
 
-const EXCLUDE_METHODS = new Set([
+const EXCLUDE_PROPERTIES = new Set([
   'Browser.create',
   'Headers.fromPayload',
   'Page.create',
   'JSHandle.toString',
+  'TimeoutError.name',
 ]);
 
 /**
@@ -137,7 +139,7 @@ function filterJSDocumentation(jsDocumentation) {
       // Exclude all constructors by default.
       if (member.name === 'constructor' && member.type === 'method')
         return false;
-      return !EXCLUDE_METHODS.has(`${cls.name}.${member.name}`);
+      return !EXCLUDE_PROPERTIES.has(`${cls.name}.${member.name}`);
     });
     classes.push(new Documentation.Class(cls.name, members));
   }
diff --git a/utils/testrunner/Matchers.js b/utils/testrunner/Matchers.js
index e6d5b434..a7d208c2 100644
--- a/utils/testrunner/Matchers.js
+++ b/utils/testrunner/Matchers.js
@@ -108,7 +108,12 @@ const DefaultMatchers = {
       pass: Math.abs(value - other) < Math.pow(10, -precision),
       message
     };
-  }
+  },
+
+  toBeInstanceOf: function(value, other, message) {
+    message = message || `${value.constructor.name} instanceof ${other.name}`;
+    return { pass: value instanceof other, message };
+  },
 };
 
 function stringify(value) {