diff --git a/components/webdriver_server/lib.rs b/components/webdriver_server/lib.rs
index 3206af03a32c..d668c17696e0 100644
--- a/components/webdriver_server/lib.rs
+++ b/components/webdriver_server/lib.rs
@@ -52,7 +52,7 @@ use util::prefs::{PREFS, PrefValue};
 use util::thread::spawn_named;
 use uuid::Uuid;
 use webdriver::command::{AddCookieParameters, GetParameters, JavascriptCommandParameters};
-use webdriver::command::{LocatorParameters, Parameters};
+use webdriver::command::{LocatorParameters, Parameters, SwitchToWindowParameters};
 use webdriver::command::{SendKeysParameters, SwitchToFrameParameters, TimeoutsParameters};
 use webdriver::command::{WebDriverCommand, WebDriverExtensionCommand, WebDriverMessage};
 use webdriver::command::WindowSizeParameters;
@@ -504,6 +504,20 @@ impl Handler {
         }
     }
 
+    fn handle_dismiss_alert(&mut self) -> WebDriverResult<WebDriverResponse> {
+        //TODO figure out how to interact with blocking native UI
+        Ok(WebDriverResponse::Void)
+    }
+
+    fn handle_switch_to_window(&mut self, parameters: &SwitchToWindowParameters) -> WebDriverResult<WebDriverResponse> {
+        if parameters.handle == self.session.as_ref().unwrap().id.to_string() {
+            Ok(WebDriverResponse::Void)
+        } else {
+            Err(WebDriverError::new(ErrorStatus::UnsupportedOperation,
+                                    "Switching to another window is not supported"))
+        }
+    }
+
     fn handle_switch_to_frame(&mut self, parameters: &SwitchToFrameParameters) -> WebDriverResult<WebDriverResponse> {
         use webdriver::common::FrameId;
         let frame_id = match parameters.id {
@@ -873,6 +887,7 @@ impl WebDriverHandler<ServoExtensionRoute> for Handler {
             WebDriverCommand::GetTitle => self.handle_title(),
             WebDriverCommand::GetWindowHandle => self.handle_window_handle(),
             WebDriverCommand::GetWindowHandles => self.handle_window_handles(),
+            WebDriverCommand::SwitchToWindow(ref parameters) => self.handle_switch_to_window(parameters),
             WebDriverCommand::SwitchToFrame(ref parameters) => self.handle_switch_to_frame(parameters),
             WebDriverCommand::SwitchToParentFrame => self.handle_switch_to_parent_frame(),
             WebDriverCommand::FindElement(ref parameters) => self.handle_find_element(parameters),
@@ -900,6 +915,7 @@ impl WebDriverHandler<ServoExtensionRoute> for Handler {
                     ServoExtensionCommand::ResetPrefs(ref x) => self.handle_reset_prefs(x),
                 }
             }
+            WebDriverCommand::DismissAlert => self.handle_dismiss_alert(),
             _ => Err(WebDriverError::new(ErrorStatus::UnsupportedOperation,
                                          "Command not implemented"))
         }
diff --git a/python/servo/devenv_commands.py b/python/servo/devenv_commands.py
index 2fc4a08e434b..a8a20a93fcc4 100644
--- a/python/servo/devenv_commands.py
+++ b/python/servo/devenv_commands.py
@@ -168,25 +168,28 @@ def fetch(self):
                 print(cargo_path)
                 call(["cargo", "fetch"], env=self.build_env())
 
-    @Command('wpt-upgrade',
+    @Command('wptrunner-upgrade',
              description='upgrade wptrunner.',
              category='devenv')
     def upgrade_wpt_runner(self):
+        env = self.build_env()
         with cd(path.join(self.context.topdir, 'tests', 'wpt', 'harness')):
-            code = call(["git", "init"], env=self.build_env())
+            code = call(["git", "init"], env=env)
             if code:
                 return code
+            # No need to report an error if this fails, as it will for the first use
+            call(["git", "remote", "rm", "upstream"], env=env)
             code = call(
-                ["git", "remote", "add", "upstream", "https://github.com/w3c/wptrunner.git"], env=self.build_env())
+                ["git", "remote", "add", "upstream", "https://github.com/w3c/wptrunner.git"], env=env)
             if code:
                 return code
-            code = call(["git", "fetch", "upstream"], env=self.build_env())
+            code = call(["git", "fetch", "upstream"], env=env)
             if code:
                 return code
-            code = call(["git", "reset", "--hard", "remotes/upstream/master"], env=self.build_env())
+            code = call(["git", "reset", "--hard", "remotes/upstream/master"], env=env)
             if code:
                 return code
-            code = call(["rm", "-rf", ".git"], env=self.build_env())
+            code = call(["rm", "-rf", ".git"], env=env)
             if code:
                 return code
             return 0
diff --git a/tests/wpt/harness/wptrunner/browsers/__init__.py b/tests/wpt/harness/wptrunner/browsers/__init__.py
index ffc5aedc8304..2433e42ada1c 100644
--- a/tests/wpt/harness/wptrunner/browsers/__init__.py
+++ b/tests/wpt/harness/wptrunner/browsers/__init__.py
@@ -28,6 +28,7 @@
 
 product_list = ["b2g",
                 "chrome",
+                "edge",
                 "firefox",
                 "servo",
                 "servodriver"]
diff --git a/tests/wpt/harness/wptrunner/browsers/firefox.py b/tests/wpt/harness/wptrunner/browsers/firefox.py
index dcd7a4f1d17d..a3c6f3f5753f 100644
--- a/tests/wpt/harness/wptrunner/browsers/firefox.py
+++ b/tests/wpt/harness/wptrunner/browsers/firefox.py
@@ -3,6 +3,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import os
+import platform
 import subprocess
 import sys
 
@@ -128,10 +129,16 @@ def start(self):
         self.profile.set_preferences({"marionette.defaultPrefs.enabled": True,
                                       "marionette.defaultPrefs.port": self.marionette_port,
                                       "dom.disable_open_during_load": False,
-                                      "network.dns.localDomains": ",".join(hostnames)})
+                                      "network.dns.localDomains": ",".join(hostnames),
+                                      "places.history.enabled": False})
         if self.e10s:
             self.profile.set_preferences({"browser.tabs.remote.autostart": True})
 
+        # Bug 1262954: winxp + e10s, disable hwaccel
+        if (self.e10s and platform.system() in ("Windows", "Microsoft") and
+            '5.1' in platform.version()):
+            self.profile.set_preferences({"layers.acceleration.disabled": True})
+
         if self.ca_certificate_path is not None:
             self.setup_ssl()
 
diff --git a/tests/wpt/harness/wptrunner/browsers/servo.py b/tests/wpt/harness/wptrunner/browsers/servo.py
index bc90cefcfc9e..4e4bc20128c4 100644
--- a/tests/wpt/harness/wptrunner/browsers/servo.py
+++ b/tests/wpt/harness/wptrunner/browsers/servo.py
@@ -6,7 +6,7 @@
 
 from .base import NullBrowser, ExecutorBrowser, require_arg
 from ..executors import executor_kwargs as base_executor_kwargs
-from ..executors.executorservo import ServoTestharnessExecutor, ServoRefTestExecutor
+from ..executors.executorservo import ServoTestharnessExecutor, ServoRefTestExecutor, ServoWdspecExecutor
 
 here = os.path.join(os.path.split(__file__)[0])
 
@@ -14,7 +14,8 @@
                  "check_args": "check_args",
                  "browser": "ServoBrowser",
                  "executor": {"testharness": "ServoTestharnessExecutor",
-                              "reftest": "ServoRefTestExecutor"},
+                              "reftest": "ServoRefTestExecutor",
+                              "wdspec": "ServoWdspecExecutor"},
                  "browser_kwargs": "browser_kwargs",
                  "executor_kwargs": "executor_kwargs",
                  "env_options": "env_options",
diff --git a/tests/wpt/harness/wptrunner/executors/executormarionette.py b/tests/wpt/harness/wptrunner/executors/executormarionette.py
index c4b1cba689af..8fc8ebed8130 100644
--- a/tests/wpt/harness/wptrunner/executors/executormarionette.py
+++ b/tests/wpt/harness/wptrunner/executors/executormarionette.py
@@ -17,11 +17,11 @@
 
 errors = None
 marionette = None
+pytestrunner = None
 webdriver = None
 
 here = os.path.join(os.path.split(__file__)[0])
 
-from . import pytestrunner
 from .base import (ExecutorException,
                    Protocol,
                    RefTestExecutor,
@@ -41,7 +41,7 @@
 
 
 def do_delayed_imports():
-    global errors, marionette, webdriver
+    global errors, marionette
 
     # Marionette client used to be called marionette, recently it changed
     # to marionette_driver for unfathomable reasons
@@ -51,8 +51,6 @@ def do_delayed_imports():
     except ImportError:
         from marionette_driver import marionette, errors
 
-    import webdriver
-
 
 class MarionetteProtocol(Protocol):
     def __init__(self, executor, browser):
@@ -292,7 +290,7 @@ def is_alive(self):
 class ExecuteAsyncScriptRun(object):
     def __init__(self, logger, func, marionette, url, timeout):
         self.logger = logger
-        self.result = None
+        self.result = (None, None)
         self.marionette = marionette
         self.func = func
         self.url = url
@@ -323,11 +321,9 @@ def run(self):
             wait_timeout = None
 
         flag = self.result_flag.wait(wait_timeout)
-        if self.result is None:
+        if self.result[1] is None:
             self.logger.debug("Timed out waiting for a result")
-            assert not flag
             self.result = False, ("EXTERNAL-TIMEOUT", None)
-
         return self.result
 
     def _run(self):
@@ -409,7 +405,8 @@ def do_testharness(self, marionette, url, timeout):
                                 "timeout": timeout_ms,
                                 "explicit_timeout": timeout is None}
 
-        return marionette.execute_async_script(script, new_sandbox=False)
+        rv = marionette.execute_async_script(script, new_sandbox=False)
+        return rv
 
 
 class MarionetteRefTestExecutor(RefTestExecutor):
@@ -487,7 +484,7 @@ def _screenshot(self, marionette, url, timeout):
 class WdspecRun(object):
     def __init__(self, func, session, path, timeout):
         self.func = func
-        self.result = None
+        self.result = (None, None)
         self.session = session
         self.path = path
         self.timeout = timeout
@@ -504,8 +501,7 @@ def run(self):
         executor.start()
 
         flag = self.result_flag.wait(self.timeout)
-        if self.result is None:
-            assert not flag
+        if self.result[1] is None:
             self.result = False, ("EXTERNAL-TIMEOUT", None)
 
         return self.result
@@ -528,6 +524,7 @@ def _run(self):
 class MarionetteWdspecExecutor(WdspecExecutor):
     def __init__(self, browser, server_config, webdriver_binary,
                  timeout_multiplier=1, close_after_done=True, debug_info=None):
+        self.do_delayed_imports()
         WdspecExecutor.__init__(self, browser, server_config,
                                 timeout_multiplier=timeout_multiplier,
                                 debug_info=debug_info)
@@ -557,3 +554,8 @@ def do_wdspec(self, session, path, timeout):
         harness_result = ("OK", None)
         subtest_results = pytestrunner.run(path, session, timeout=timeout)
         return (harness_result, subtest_results)
+
+    def do_delayed_imports(self):
+        global pytestrunner, webdriver
+        from . import pytestrunner
+        from tools import webdriver
diff --git a/tests/wpt/harness/wptrunner/executors/executorselenium.py b/tests/wpt/harness/wptrunner/executors/executorselenium.py
index 587c49c7c92f..f5d65f499b0a 100644
--- a/tests/wpt/harness/wptrunner/executors/executorselenium.py
+++ b/tests/wpt/harness/wptrunner/executors/executorselenium.py
@@ -22,20 +22,21 @@
                    strip_server)
 from ..testrunner import Stop
 
-
 here = os.path.join(os.path.split(__file__)[0])
 
 webdriver = None
 exceptions = None
+RemoteConnection = None
 
 extra_timeout = 5
 
 def do_delayed_imports():
     global webdriver
     global exceptions
+    global RemoteConnection
     from selenium import webdriver
     from selenium.common import exceptions
-
+    from selenium.webdriver.remote.remote_connection import RemoteConnection
 
 class SeleniumProtocol(Protocol):
     def __init__(self, executor, browser, capabilities, **kwargs):
@@ -53,8 +54,9 @@ def setup(self, runner):
 
         session_started = False
         try:
-            self.webdriver = webdriver.Remote(
-                self.url, desired_capabilities=self.capabilities)
+            self.webdriver = webdriver.Remote(command_executor=RemoteConnection(self.url.strip("/"),
+                                                                                resolve_ip=False),
+                                              desired_capabilities=self.capabilities)
         except:
             self.logger.warning(
                 "Connecting to Selenium failed:\n%s" % traceback.format_exc())
@@ -231,17 +233,7 @@ def is_alive(self):
     def do_test(self, test):
         self.logger.info("Test requires OS-level window focus")
 
-        if self.close_after_done and self.has_window:
-            self.protocol.webdriver.close()
-            self.protocol.webdriver.switch_to_window(
-                self.protocol.webdriver.window_handles[-1])
-            self.has_window = False
-
-        if not self.has_window:
-            self.protocol.webdriver.execute_script(self.script)
-            self.protocol.webdriver.switch_to_window(
-                self.protocol.webdriver.window_handles[-1])
-            self.has_window = True
+        self.protocol.webdriver.set_window_size(600, 600)
 
         result = self.implementation.run_test(test)
 
diff --git a/tests/wpt/harness/wptrunner/executors/executorservo.py b/tests/wpt/harness/wptrunner/executors/executorservo.py
index ca684d4ef22c..b0c4d5afea3a 100644
--- a/tests/wpt/harness/wptrunner/executors/executorservo.py
+++ b/tests/wpt/harness/wptrunner/executors/executorservo.py
@@ -4,11 +4,13 @@
 
 import base64
 import hashlib
+import httplib
 import json
 import os
 import subprocess
 import tempfile
 import threading
+import traceback
 import urlparse
 import uuid
 from collections import defaultdict
@@ -19,11 +21,19 @@
                    Protocol,
                    RefTestImplementation,
                    testharness_result_converter,
-                   reftest_result_converter)
+                   reftest_result_converter,
+                   WdspecExecutor)
 from .process import ProcessTestExecutor
 from ..browsers.base import browser_command
+from ..wpttest import WdspecResult, WdspecSubtestResult
+from ..webdriver_server import ServoDriverServer
+from .executormarionette import WdspecRun
+
+pytestrunner = None
 render_arg = None
+webdriver = None
 
+extra_timeout = 5 # seconds
 
 def do_delayed_imports():
     global render_arg
@@ -214,10 +224,7 @@ def screenshot(self, test, viewport_size, dpi):
             for pref, value in test.environment.get('prefs', {}).iteritems():
                 command += ["--pref", "%s=%s" % (pref, value)]
 
-            if viewport_size:
-                command += ["--resolution", viewport_size]
-            else:
-                command += ["--resolution", "800x600"]
+            command += ["--resolution", viewport_size or "800x600"]
 
             if dpi:
                 command += ["--device-pixel-ratio", dpi]
@@ -275,3 +282,84 @@ def on_output(self, line):
             self.logger.process_output(self.proc.pid,
                                        line,
                                        " ".join(self.command))
+
+class ServoWdspecProtocol(Protocol):
+    def __init__(self, executor, browser):
+        self.do_delayed_imports()
+        Protocol.__init__(self, executor, browser)
+        self.session = None
+        self.server = None
+
+    def setup(self, runner):
+        try:
+            self.server = ServoDriverServer(self.logger, binary=self.browser.binary, binary_args=self.browser.binary_args, render_backend=self.browser.render_backend)
+            self.server.start(block=False)
+            self.logger.info(
+                "WebDriver HTTP server listening at %s" % self.server.url)
+
+            self.logger.info(
+                "Establishing new WebDriver session with %s" % self.server.url)
+            self.session = webdriver.Session(
+                self.server.host, self.server.port, self.server.base_path)
+            self.session.start()
+        except Exception:
+            self.logger.error(traceback.format_exc())
+            self.executor.runner.send_message("init_failed")
+        else:
+            self.executor.runner.send_message("init_succeeded")
+
+    def teardown(self):
+        if self.server is not None:
+            try:
+                if self.session.session_id is not None:
+                    self.session.end()
+            except Exception:
+                pass
+            if self.server.is_alive:
+                self.server.stop()
+
+    @property
+    def is_alive(self):
+        conn = httplib.HTTPConnection(self.server.host, self.server.port)
+        conn.request("HEAD", self.server.base_path + "invalid")
+        res = conn.getresponse()
+        return res.status == 404
+
+    def do_delayed_imports(self):
+        global pytestrunner, webdriver
+        from . import pytestrunner
+        import webdriver
+
+
+class ServoWdspecExecutor(WdspecExecutor):
+    def __init__(self, browser, server_config,
+                 timeout_multiplier=1, close_after_done=True, debug_info=None,
+                 **kwargs):
+        WdspecExecutor.__init__(self, browser, server_config,
+                                timeout_multiplier=timeout_multiplier,
+                                debug_info=debug_info)
+        self.protocol = ServoWdspecProtocol(self, browser)
+
+    def is_alive(self):
+        return self.protocol.is_alive
+
+    def on_environment_change(self, new_environment):
+        pass
+
+    def do_test(self, test):
+        timeout = test.timeout * self.timeout_multiplier + extra_timeout
+
+        success, data = WdspecRun(self.do_wdspec,
+                                  self.protocol.session,
+                                  test.path,
+                                  timeout).run()
+
+        if success:
+            return self.convert_result(test, data)
+
+        return (test.result_cls(*data), [])
+
+    def do_wdspec(self, session, path, timeout):
+        harness_result = ("OK", None)
+        subtest_results = pytestrunner.run(path, session, timeout=timeout)
+        return (harness_result, subtest_results)
diff --git a/tests/wpt/harness/wptrunner/executors/executorservodriver.py b/tests/wpt/harness/wptrunner/executors/executorservodriver.py
index fceeb58fad2f..279658d0cd1f 100644
--- a/tests/wpt/harness/wptrunner/executors/executorservodriver.py
+++ b/tests/wpt/harness/wptrunner/executors/executorservodriver.py
@@ -14,7 +14,6 @@
                    RefTestImplementation,
                    TestharnessExecutor,
                    strip_server)
-from .. import webdriver
 from ..testrunner import Stop
 
 webdriver = None
@@ -26,7 +25,7 @@
 
 def do_delayed_imports():
     global webdriver
-    import webdriver
+    from tools import webdriver
 
 
 class ServoWebDriverProtocol(Protocol):
diff --git a/tests/wpt/harness/wptrunner/executors/pytestrunner/fixtures.py b/tests/wpt/harness/wptrunner/executors/pytestrunner/fixtures.py
index 77afb4a36842..bda42fe06445 100644
--- a/tests/wpt/harness/wptrunner/executors/pytestrunner/fixtures.py
+++ b/tests/wpt/harness/wptrunner/executors/pytestrunner/fixtures.py
@@ -3,6 +3,7 @@
 # You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import pytest
+import webdriver
 
 
 """pytest fixtures for use in Python-based WPT tests.
@@ -17,7 +18,7 @@ class Session(object):
     in tests.
 
     The session is not created by default to enable testing of session
-    creation.  However, a module-scoped session will be implicitly created
+    creation.  However, a function-scoped session will be implicitly created
     at the first call to a WebDriver command.  This means methods such as
     `session.send_command` and `session.session_id` are possible to use
     without having a session.
@@ -45,14 +46,62 @@ def setup(request, session):
         def test_something(setup, session):
             assert session.url == "https://example.org"
 
-    The session is closed when the test module goes out of scope by an
-    implicit call to `session.end`.
+    When the test function goes out of scope, any remaining user prompts
+    and opened windows are closed, and the current browsing context is
+    switched back to the top-level browsing context.
     """
 
     def __init__(self, client):
         self.client = client
 
-    @pytest.fixture(scope="module")
+    @pytest.fixture(scope="function")
     def session(self, request):
-        request.addfinalizer(self.client.end)
+        # finalisers are popped off a stack,
+        # making their ordering reverse
+        request.addfinalizer(self.switch_to_top_level_browsing_context)
+        request.addfinalizer(self.restore_windows)
+        request.addfinalizer(self.dismiss_user_prompts)
+
         return self.client
+
+    def dismiss_user_prompts(self):
+        """Dismisses any open user prompts in windows."""
+        current_window = self.client.handle
+
+        for window in self.windows():
+            self.client.handle = window
+            try:
+                self.client.alert.dismiss()
+            except webdriver.NoSuchAlertException:
+                pass
+
+        self.client.handle = current_window
+
+    def restore_windows(self):
+        """Closes superfluous windows opened by the test without ending
+        the session implicitly by closing the last window.
+        """
+        current_window = self.client.handle
+
+        for window in self.windows(exclude=[current_window]):
+            self.client.handle = window
+            if len(self.client.handles) > 1:
+                self.client.close()
+
+        self.client.handle = current_window
+
+    def switch_to_top_level_browsing_context(self):
+        """If the current browsing context selected by WebDriver is a
+        `<frame>` or an `<iframe>`, switch it back to the top-level
+        browsing context.
+        """
+        self.client.switch_frame(None)
+
+    def windows(self, exclude=None):
+        """Set of window handles, filtered by an `exclude` list if
+        provided.
+        """
+        if exclude is None:
+            exclude = []
+        wins = [w for w in self.client.handles if w not in exclude]
+        return set(wins)
diff --git a/tests/wpt/harness/wptrunner/executors/testharness_webdriver.js b/tests/wpt/harness/wptrunner/executors/testharness_webdriver.js
index 7ca8d5737032..f78f9aef05b7 100644
--- a/tests/wpt/harness/wptrunner/executors/testharness_webdriver.js
+++ b/tests/wpt/harness/wptrunner/executors/testharness_webdriver.js
@@ -5,14 +5,18 @@
 var callback = arguments[arguments.length - 1];
 window.timeout_multiplier = %(timeout_multiplier)d;
 
-window.addEventListener("message", function(event) {
-  var tests = event.data[0];
-  var status = event.data[1];
+window.addEventListener("message", function f(event) {
+  if (event.data.type != "complete") {
+    return;
+  }
+  window.removeEventListener("message", f);
+
+  var tests = event.data.tests;
+  var status = event.data.status;
 
   var subtest_results = tests.map(function(x) {
-      return [x.name, x.status, x.message, x.stack]
+    return [x.name, x.status, x.message, x.stack]
   });
-
   clearTimeout(timer);
   callback(["%(url)s",
             status.status,
diff --git a/tests/wpt/harness/wptrunner/executors/webdriver.py b/tests/wpt/harness/wptrunner/executors/webdriver.py
index dee2a1c23378..4de3de22e812 100644
--- a/tests/wpt/harness/wptrunner/executors/webdriver.py
+++ b/tests/wpt/harness/wptrunner/executors/webdriver.py
@@ -177,7 +177,7 @@ def __init__(self, host, port, url_prefix="", port_timeout=60):
         self.host = host
         self.port = port
         self.port_timeout = port_timeout
-        if url_prefix == "":
+        if url_prefix == "" or url_prefix == "/":
             self.path_prefix = "/"
         else:
             self.path_prefix = "/%s/" % url_prefix.strip("/")
@@ -385,6 +385,7 @@ def start(self):
         self.timeouts = Timeouts(self)
         self.window = Window(self)
         self.find = Find(self)
+        self.alert = Alert(self)
         if self.extension_cls:
             self.extension = self.extension_cls(self)
 
@@ -622,6 +623,16 @@ def rect(self):
     def attribute(self, name):
         return self.session.send_command("GET", self.url("attribute/%s" % name))
 
+
+class Alert(object):
+    def __init__(self, session):
+        self.session = session
+
+    @command
+    def dismiss(self):
+        return self.session.send_command("POST", "alert/dismiss")
+
+
 class ServoExtensions(object):
     def __init__(self, session):
         self.session = session
diff --git a/tests/wpt/harness/wptrunner/testrunner.py b/tests/wpt/harness/wptrunner/testrunner.py
index 77d2a8850834..38cc42203102 100644
--- a/tests/wpt/harness/wptrunner/testrunner.py
+++ b/tests/wpt/harness/wptrunner/testrunner.py
@@ -168,7 +168,7 @@ class TestRunnerManager(threading.Thread):
 
     def __init__(self, suite_name, test_queue, test_source_cls, browser_cls, browser_kwargs,
                  executor_cls, executor_kwargs, stop_flag, pause_after_test=False,
-                 pause_on_unexpected=False, debug_info=None):
+                 pause_on_unexpected=False, restart_on_unexpected=True, debug_info=None):
         """Thread that owns a single TestRunner process and any processes required
         by the TestRunner (e.g. the Firefox binary).
 
@@ -207,6 +207,7 @@ def __init__(self, suite_name, test_queue, test_source_cls, browser_cls, browser
 
         self.pause_after_test = pause_after_test
         self.pause_on_unexpected = pause_on_unexpected
+        self.restart_on_unexpected = restart_on_unexpected
         self.debug_info = debug_info
 
         self.manager_number = next_manager_number()
@@ -526,7 +527,8 @@ def test_ended(self, test, results):
 
         restart_before_next = (test.restart_after or
                                file_result.status in ("CRASH", "EXTERNAL-TIMEOUT") or
-                               subtest_unexpected or is_unexpected)
+                               ((subtest_unexpected or is_unexpected)
+                                and self.restart_on_unexpected))
 
         if (self.pause_after_test or
             (self.pause_on_unexpected and (subtest_unexpected or is_unexpected))):
@@ -593,6 +595,7 @@ def __init__(self, suite_name, size, test_source_cls, test_source_kwargs,
                  executor_cls, executor_kwargs,
                  pause_after_test=False,
                  pause_on_unexpected=False,
+                 restart_on_unexpected=True,
                  debug_info=None):
         """Main thread object that owns all the TestManager threads."""
         self.suite_name = suite_name
@@ -605,6 +608,7 @@ def __init__(self, suite_name, size, test_source_cls, test_source_kwargs,
         self.executor_kwargs = executor_kwargs
         self.pause_after_test = pause_after_test
         self.pause_on_unexpected = pause_on_unexpected
+        self.restart_on_unexpected = restart_on_unexpected
         self.debug_info = debug_info
 
         self.pool = set()
@@ -643,6 +647,7 @@ def run(self, test_type, tests):
                                             self.stop_flag,
                                             self.pause_after_test,
                                             self.pause_on_unexpected,
+                                            self.restart_on_unexpected,
                                             self.debug_info)
                 manager.start()
                 self.pool.add(manager)
diff --git a/tests/wpt/harness/wptrunner/tests/test_chunker.py b/tests/wpt/harness/wptrunner/tests/test_chunker.py
index d46ad2587838..84af2dc67ef6 100644
--- a/tests/wpt/harness/wptrunner/tests/test_chunker.py
+++ b/tests/wpt/harness/wptrunner/tests/test_chunker.py
@@ -4,7 +4,11 @@
 
 import unittest
 import sys
-sys.path.insert(0, "..")
+from os.path import join, dirname
+
+import pytest
+
+sys.path.insert(0, join(dirname(__file__), "..", ".."))
 
 from wptrunner import wptrunner
 
@@ -25,6 +29,7 @@ def make_mock_manifest(*items):
 
 class TestEqualTimeChunker(unittest.TestCase):
 
+    @pytest.mark.xfail
     def test_include_all(self):
         tests = make_mock_manifest(("a", 10), ("a/b", 10), ("c", 10))
 
@@ -36,6 +41,7 @@ def test_include_all(self):
         self.assertEquals(tests[10:20], chunk_2)
         self.assertEquals(tests[20:], chunk_3)
 
+    @pytest.mark.xfail
     def test_include_all_1(self):
         tests = make_mock_manifest(("a", 5), ("a/b", 5), ("c", 10), ("d", 10))
 
@@ -47,6 +53,7 @@ def test_include_all_1(self):
         self.assertEquals(tests[10:20], chunk_2)
         self.assertEquals(tests[20:], chunk_3)
 
+    @pytest.mark.xfail
     def test_long(self):
         tests = make_mock_manifest(("a", 100), ("a/b", 1), ("c", 1))
 
@@ -58,6 +65,7 @@ def test_long(self):
         self.assertEquals(tests[100:101], chunk_2)
         self.assertEquals(tests[101:102], chunk_3)
 
+    @pytest.mark.xfail
     def test_long_1(self):
         tests = make_mock_manifest(("a", 1), ("a/b", 100), ("c", 1))
 
@@ -69,6 +77,7 @@ def test_long_1(self):
         self.assertEquals(tests[1:101], chunk_2)
         self.assertEquals(tests[101:102], chunk_3)
 
+    @pytest.mark.xfail
     def test_too_few_dirs(self):
         with self.assertRaises(ValueError):
             tests = make_mock_manifest(("a", 1), ("a/b", 100), ("c", 1))
diff --git a/tests/wpt/harness/wptrunner/tests/test_hosts.py b/tests/wpt/harness/wptrunner/tests/test_hosts.py
index 4f122640d58a..3f9006273df8 100644
--- a/tests/wpt/harness/wptrunner/tests/test_hosts.py
+++ b/tests/wpt/harness/wptrunner/tests/test_hosts.py
@@ -4,11 +4,12 @@
 
 import unittest
 import sys
+from os.path import join, dirname
 from cStringIO import StringIO
 
-sys.path.insert(0, "..")
+sys.path.insert(0, join(dirname(__file__), "..", ".."))
 
-import hosts
+from wptrunner import hosts
 
 
 class HostsTest(unittest.TestCase):
diff --git a/tests/wpt/harness/wptrunner/tests/test_update.py b/tests/wpt/harness/wptrunner/tests/test_update.py
index 2d77b326d615..50878ac56dc0 100644
--- a/tests/wpt/harness/wptrunner/tests/test_update.py
+++ b/tests/wpt/harness/wptrunner/tests/test_update.py
@@ -5,6 +5,8 @@
 import unittest
 import StringIO
 
+import pytest
+
 from .. import metadata, manifestupdate
 from mozlog import structuredlog, handlers, formatters
 
@@ -51,6 +53,7 @@ def coalesce_results(self, trees):
                     subtest.coalesce_expected()
                 test.coalesce_expected()
 
+    @pytest.mark.xfail
     def test_update_0(self):
         prev_data = [("path/to/test.htm.ini", ["/path/to/test.htm"], """[test.htm]
   type: testharness
@@ -71,6 +74,7 @@ def test_update_0(self):
         self.coalesce_results([new_manifest])
         self.assertTrue(new_manifest.is_empty)
 
+    @pytest.mark.xfail
     def test_update_1(self):
         test_id = "/path/to/test.htm"
         prev_data = [("path/to/test.htm.ini", [test_id], """[test.htm]
@@ -93,6 +97,7 @@ def test_update_1(self):
         self.assertFalse(new_manifest.is_empty)
         self.assertEquals(new_manifest.get_test(test_id).children[0].get("expected"), "FAIL")
 
+    @pytest.mark.xfail
     def test_new_subtest(self):
         test_id = "/path/to/test.htm"
         prev_data = [("path/to/test.htm.ini", [test_id], """[test.htm]
@@ -120,6 +125,7 @@ def test_new_subtest(self):
         self.assertEquals(new_manifest.get_test(test_id).children[0].get("expected"), "FAIL")
         self.assertEquals(new_manifest.get_test(test_id).children[1].get("expected"), "FAIL")
 
+    @pytest.mark.xfail
     def test_update_multiple_0(self):
         test_id = "/path/to/test.htm"
         prev_data = [("path/to/test.htm.ini", [test_id], """[test.htm]
@@ -159,6 +165,7 @@ def test_update_multiple_0(self):
         self.assertEquals(new_manifest.get_test(test_id).children[0].get(
             "expected", {"debug": False, "os": "linux"}), "TIMEOUT")
 
+    @pytest.mark.xfail
     def test_update_multiple_1(self):
         test_id = "/path/to/test.htm"
         prev_data = [("path/to/test.htm.ini", [test_id], """[test.htm]
@@ -200,6 +207,7 @@ def test_update_multiple_1(self):
         self.assertEquals(new_manifest.get_test(test_id).children[0].get(
             "expected", {"debug": False, "os": "windows"}), "FAIL")
 
+    @pytest.mark.xfail
     def test_update_multiple_2(self):
         test_id = "/path/to/test.htm"
         prev_data = [("path/to/test.htm.ini", [test_id], """[test.htm]
@@ -239,6 +247,7 @@ def test_update_multiple_2(self):
         self.assertEquals(new_manifest.get_test(test_id).children[0].get(
             "expected", {"debug": True, "os": "osx"}), "TIMEOUT")
 
+    @pytest.mark.xfail
     def test_update_multiple_3(self):
         test_id = "/path/to/test.htm"
         prev_data = [("path/to/test.htm.ini", [test_id], """[test.htm]
@@ -280,6 +289,7 @@ def test_update_multiple_3(self):
         self.assertEquals(new_manifest.get_test(test_id).children[0].get(
             "expected", {"debug": True, "os": "osx"}), "TIMEOUT")
 
+    @pytest.mark.xfail
     def test_update_ignore_existing(self):
         test_id = "/path/to/test.htm"
         prev_data = [("path/to/test.htm.ini", [test_id], """[test.htm]
diff --git a/tests/wpt/harness/wptrunner/webdriver_server.py b/tests/wpt/harness/wptrunner/webdriver_server.py
index 68d3fb7a3bfd..2e660b51e087 100644
--- a/tests/wpt/harness/wptrunner/webdriver_server.py
+++ b/tests/wpt/harness/wptrunner/webdriver_server.py
@@ -16,7 +16,8 @@
 
 
 __all__ = ["SeleniumServer", "ChromeDriverServer",
-           "GeckoDriverServer", "WebDriverServer"]
+           "GeckoDriverServer", "ServoDriverServer",
+           "WebDriverServer"]
 
 
 class WebDriverServer(object):
@@ -44,7 +45,7 @@ def __init__(self, logger, binary, host="127.0.0.1", port=None,
     def make_command(self):
         """Returns the full command for starting the server process as a list."""
 
-    def start(self, block=True):
+    def start(self, block=False):
         try:
             self._run(block)
         except KeyboardInterrupt:
@@ -86,9 +87,7 @@ def stop(self):
 
     @property
     def is_alive(self):
-        return (self._proc is not None and
-                self._proc.proc is not None and
-                self._proc.poll() is None)
+        return hasattr(self._proc, "proc") and self._proc.poll() is None
 
     def on_output(self, line):
         self.logger.process_output(self.pid,
@@ -138,6 +137,17 @@ def make_command(self):
                 cmd_arg("url-base", self.base_path) if self.base_path else ""]
 
 
+class EdgeDriverServer(WebDriverServer):
+    def __init__(self, logger, binary="MicrosoftWebDriver.exe", port=None,
+                 base_path="", host="localhost"):
+        WebDriverServer.__init__(
+            self, logger, binary, host=host, port=port)
+
+    def make_command(self):
+        return [self.binary,
+                "--port=%s" % str(self.port)]
+
+
 class GeckoDriverServer(WebDriverServer):
     def __init__(self, logger, marionette_port=2828, binary="wires",
                  host="127.0.0.1", port=None):
@@ -154,6 +164,28 @@ def make_command(self):
                 "--webdriver-port", str(self.port)]
 
 
+class ServoDriverServer(WebDriverServer):
+    def __init__(self, logger, binary="servo", binary_args=None, host="127.0.0.1", port=None, render_backend=None):
+        env = os.environ.copy()
+        env["RUST_BACKTRACE"] = "1"
+        WebDriverServer.__init__(self, logger, binary, host=host, port=port, env=env)
+        self.binary_args = binary_args
+        self.render_backend = render_backend
+
+    def make_command(self):
+        command = [self.binary,
+                   "--webdriver", str(self.port),
+                   "--hard-fail",
+                   "--headless"]
+        if self.binary_args:
+            command += self.binary_args
+        if self.render_backend == "cpu":
+            command += ["--cpu"]
+        elif self.render_backend == "webrender":
+            command += ["--webrender"]
+        return command
+
+
 def cmd_arg(name, value=None):
     prefix = "-" if platform.system() == "Windows" else "--"
     rv = prefix + name
diff --git a/tests/wpt/harness/wptrunner/wptcommandline.py b/tests/wpt/harness/wptrunner/wptcommandline.py
index 3b059378e09a..bbae8205b32f 100644
--- a/tests/wpt/harness/wptrunner/wptcommandline.py
+++ b/tests/wpt/harness/wptrunner/wptcommandline.py
@@ -45,61 +45,33 @@ def create_parser(product_choices=None):
         config_data = config.load()
         product_choices = products.products_enabled(config_data)
 
-    parser = argparse.ArgumentParser(description="Runner for web-platform-tests tests.")
-    parser.add_argument("--metadata", action="store", type=abs_path, dest="metadata_root",
-                        help="Path to the folder containing test metadata"),
-    parser.add_argument("--tests", action="store", type=abs_path, dest="tests_root",
-                        help="Path to test files"),
-    parser.add_argument("--run-info", action="store", type=abs_path,
-                        help="Path to directory containing extra json files to add to run info")
-    parser.add_argument("--config", action="store", type=abs_path, dest="config",
-                        help="Path to config file")
+    parser = argparse.ArgumentParser(description="""Runner for web-platform-tests tests.""",
+                                     usage="""%(prog)s [OPTION]... [TEST]...
 
+TEST is either the full path to a test file to run, or the URL of a test excluding
+scheme host and port.""")
     parser.add_argument("--manifest-update", action="store_true", default=False,
-                        help="Force regeneration of the test manifest")
-
-    parser.add_argument("--binary", action="store",
-                        type=abs_path, help="Binary to run tests against")
-    parser.add_argument('--binary-arg',
-                        default=[], action="append", dest="binary_args",
-                        help="Extra argument for the binary (servo)")
-    parser.add_argument("--webdriver-binary", action="store", metavar="BINARY",
-                        type=abs_path, help="WebDriver server binary to use")
-    parser.add_argument("--processes", action="store", type=int, default=None,
-                        help="Number of simultaneous processes to use")
+                        help="Regenerate the test manifest.")
 
+    parser.add_argument("--timeout-multiplier", action="store", type=float, default=None,
+                        help="Multiplier relative to standard test timeout to use")
     parser.add_argument("--run-by-dir", type=int, nargs="?", default=False,
                         help="Split run into groups by directories. With a parameter,"
                         "limit the depth of splits e.g. --run-by-dir=1 to split by top-level"
                         "directory")
-
-    parser.add_argument("--timeout-multiplier", action="store", type=float, default=None,
-                        help="Multiplier relative to standard test timeout to use")
-    parser.add_argument("--repeat", action="store", type=int, default=1,
-                        help="Number of times to run the tests")
-    parser.add_argument("--repeat-until-unexpected", action="store_true", default=None,
-                        help="Run tests in a loop until one returns an unexpected result")
+    parser.add_argument("--processes", action="store", type=int, default=None,
+                        help="Number of simultaneous processes to use")
 
     parser.add_argument("--no-capture-stdio", action="store_true", default=False,
                         help="Don't capture stdio and write to logging")
 
-    parser.add_argument("--product", action="store", choices=product_choices,
-                        default=None, help="Browser against which to run tests")
-
-    parser.add_argument("--list-test-groups", action="store_true",
-                        default=False,
-                        help="List the top level directories containing tests that will run.")
-    parser.add_argument("--list-disabled", action="store_true",
-                        default=False,
-                        help="List the tests that are disabled on the current platform")
-
-    build_type = parser.add_mutually_exclusive_group()
-    build_type.add_argument("--debug-build", dest="debug", action="store_true",
-                            default=None,
-                            help="Build is a debug build (overrides any mozinfo file)")
-    build_type.add_argument("--release-build", dest="debug", action="store_false",
-                            default=None,
-                            help="Build is a release (overrides any mozinfo file)")
+    mode_group = parser.add_argument_group("Mode")
+    mode_group.add_argument("--list-test-groups", action="store_true",
+                            default=False,
+                            help="List the top level directories containing tests that will run.")
+    mode_group.add_argument("--list-disabled", action="store_true",
+                            default=False,
+                            help="List the tests that are disabled on the current platform")
 
     test_selection_group = parser.add_argument_group("Test Selection")
     test_selection_group.add_argument("--test-types", action="store",
@@ -119,7 +91,10 @@ def create_parser(product_choices=None):
     debugging_group.add_argument('--debugger', const="__default__", nargs="?",
                                  help="run under a debugger, e.g. gdb or valgrind")
     debugging_group.add_argument('--debugger-args', help="arguments to the debugger")
-
+    debugging_group.add_argument("--repeat", action="store", type=int, default=1,
+                                 help="Number of times to run the tests")
+    debugging_group.add_argument("--repeat-until-unexpected", action="store_true", default=None,
+                                 help="Run tests in a loop until one returns an unexpected result")
     debugging_group.add_argument('--pause-after-test', action="store_true", default=None,
                                  help="Halt the test runner after each test (this happens by default if only a single test is run)")
     debugging_group.add_argument('--no-pause-after-test', dest="pause_after_test", action="store_false",
@@ -127,12 +102,47 @@ def create_parser(product_choices=None):
 
     debugging_group.add_argument('--pause-on-unexpected', action="store_true",
                                  help="Halt the test runner when an unexpected result is encountered")
+    debugging_group.add_argument('--no-restart-on-unexpected', dest="restart_on_unexpected",
+                                 default=True, action="store_false",
+                                 help="Don't restart on an unexpected result")
 
     debugging_group.add_argument("--symbols-path", action="store", type=url_or_path,
                                  help="Path or url to symbols file used to analyse crash minidumps.")
     debugging_group.add_argument("--stackwalk-binary", action="store", type=abs_path,
                                  help="Path to stackwalker program used to analyse minidumps.")
 
+    debugging_group.add_argument("--pdb", action="store_true",
+                                 help="Drop into pdb on python exception")
+
+    config_group = parser.add_argument_group("Configuration")
+    config_group.add_argument("--binary", action="store",
+                              type=abs_path, help="Binary to run tests against")
+    config_group.add_argument('--binary-arg',
+                              default=[], action="append", dest="binary_args",
+                              help="Extra argument for the binary (servo)")
+    config_group.add_argument("--webdriver-binary", action="store", metavar="BINARY",
+                              type=abs_path, help="WebDriver server binary to use")
+
+    config_group.add_argument("--metadata", action="store", type=abs_path, dest="metadata_root",
+                              help="Path to root directory containing test metadata"),
+    config_group.add_argument("--tests", action="store", type=abs_path, dest="tests_root",
+                              help="Path to root directory containing test files"),
+    config_group.add_argument("--run-info", action="store", type=abs_path,
+                              help="Path to directory containing extra json files to add to run info")
+    config_group.add_argument("--product", action="store", choices=product_choices,
+                              default=None, help="Browser against which to run tests")
+    config_group.add_argument("--config", action="store", type=abs_path, dest="config",
+                              help="Path to config file")
+
+    build_type = parser.add_mutually_exclusive_group()
+    build_type.add_argument("--debug-build", dest="debug", action="store_true",
+                            default=None,
+                            help="Build is a debug build (overrides any mozinfo file)")
+    build_type.add_argument("--release-build", dest="debug", action="store_false",
+                            default=None,
+                            help="Build is a release (overrides any mozinfo file)")
+
+
     chunking_group = parser.add_argument_group("Test Chunking")
     chunking_group.add_argument("--total-chunks", action="store", type=int, default=1,
                                 help="Total number of chunks to use")
diff --git a/tests/wpt/harness/wptrunner/wptmanifest/tests/test_serializer.py b/tests/wpt/harness/wptrunner/wptmanifest/tests/test_serializer.py
index ec4d6e2d7373..62a462c44e72 100644
--- a/tests/wpt/harness/wptrunner/wptmanifest/tests/test_serializer.py
+++ b/tests/wpt/harness/wptrunner/wptmanifest/tests/test_serializer.py
@@ -2,10 +2,13 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this file,
 # You can obtain one at http://mozilla.org/MPL/2.0/.
 
+import sys
 import unittest
 
 from cStringIO import StringIO
 
+import pytest
+
 from .. import parser, serializer
 
 
@@ -196,6 +199,7 @@ def test_escape_8(self):
                      r"""key: "#"
 """)
 
+    @pytest.mark.xfail(sys.maxunicode == 0xFFFF, reason="narrow unicode")
     def test_escape_9(self):
         self.compare(r"""key: \U10FFFFabc""",
                      u"""key: \U0010FFFFabc
diff --git a/tests/wpt/harness/wptrunner/wptrunner.py b/tests/wpt/harness/wptrunner/wptrunner.py
index 47560c83a351..d955131c5817 100644
--- a/tests/wpt/harness/wptrunner/wptrunner.py
+++ b/tests/wpt/harness/wptrunner/wptrunner.py
@@ -204,6 +204,7 @@ def run_tests(config, test_paths, product, **kwargs):
                                       executor_kwargs,
                                       kwargs["pause_after_test"],
                                       kwargs["pause_on_unexpected"],
+                                      kwargs["restart_on_unexpected"],
                                       kwargs["debug_info"]) as manager_group:
                         try:
                             manager_group.run(test_type, test_loader.tests)
diff --git a/tests/wpt/harness/wptrunner/wpttest.py b/tests/wpt/harness/wptrunner/wpttest.py
index 9832f72654ea..7985b0e5f931 100644
--- a/tests/wpt/harness/wptrunner/wpttest.py
+++ b/tests/wpt/harness/wptrunner/wpttest.py
@@ -131,7 +131,7 @@ def from_manifest(cls, manifest_item, inherit_metadata, test_metadata):
                    inherit_metadata,
                    test_metadata,
                    timeout=timeout,
-                   path=manifest_item.path,
+                   path=manifest_item.source_file.path,
                    protocol="https" if hasattr(manifest_item, "https") and manifest_item.https else "http")
 
     @property
diff --git a/tests/wpt/include.ini b/tests/wpt/include.ini
index 226ba9221be6..90a8ae1c2f4d 100644
--- a/tests/wpt/include.ini
+++ b/tests/wpt/include.ini
@@ -71,3 +71,5 @@ skip: true
   skip: false
 [XMLHttpRequest]
   skip: false
+[webdriver]
+  skip: false
\ No newline at end of file