testing/web-platform/tests/tools/wptrunner/wptrunner/testrunner.py
author Philip Jägenstedt <philip@foolip.org>
Thu, 11 Oct 2018 09:31:41 +0000
changeset 499486 e8201978a4abad1f4c8606ddad2b53d8cc2dc8ea
parent 499485 97dedc2880cb23bf939a685ea1cfd41cb1a32806
child 499523 693b05802d989054d34e7ede25ae2f3b0443007d
permissions -rw-r--r--
Bug 1497166 [wpt PR 13417] - Ignore "runner_teardown" messages in `TestRunnerManager.cleanup()`, a=testonly Automatic update from web-platform-testsIgnore "runner_teardown" messages in `TestRunnerManager.cleanup()` This is an alternative to https://github.com/web-platform-tests/wpt/pull/13409, which adds more handling around this rather than removing it. Fixes https://github.com/web-platform-tests/wpt/issues/13407. -- wpt-commits: 300f8e2c89abc98917b40e95c14f2edf1d354f99 wpt-pr: 13417

from __future__ import unicode_literals

import multiprocessing
import threading
import traceback
from Queue import Empty
from collections import namedtuple
from multiprocessing import Process, current_process, Queue

from mozlog import structuredlog

import wptlogging

# Special value used as a sentinal in various commands
Stop = object()


class MessageLogger(object):
    def __init__(self, message_func):
        self.send_message = message_func

    def _log_data(self, action, **kwargs):
        self.send_message("log", action, kwargs)

    def process_output(self, process, data, command):
        self._log_data("process_output", process=process, data=data, command=command)


def _log_func(level_name):
    def log(self, message):
        self._log_data(level_name.lower(), message=message)
    log.__doc__ = """Log a message with level %s

:param message: The string message to log
""" % level_name
    log.__name__ = str(level_name).lower()
    return log

# Create all the methods on StructuredLog for debug levels
for level_name in structuredlog.log_levels:
    setattr(MessageLogger, level_name.lower(), _log_func(level_name))


class TestRunner(object):
    def __init__(self, logger, command_queue, result_queue, executor):
        """Class implementing the main loop for running tests.

        This class delegates the job of actually running a test to the executor
        that is passed in.

        :param logger: Structured logger
        :param command_queue: subprocess.Queue used to send commands to the
                              process
        :param result_queue: subprocess.Queue used to send results to the
                             parent TestRunnerManager process
        :param executor: TestExecutor object that will actually run a test.
        """
        self.command_queue = command_queue
        self.result_queue = result_queue

        self.executor = executor
        self.name = current_process().name
        self.logger = logger

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        self.teardown()

    def setup(self):
        self.logger.debug("Executor setup")
        self.executor.setup(self)
        self.logger.debug("Executor setup done")

    def teardown(self):
        self.executor.teardown()
        self.send_message("runner_teardown")
        self.result_queue = None
        self.command_queue = None
        self.browser = None

    def run(self):
        """Main loop accepting commands over the pipe and triggering
        the associated methods"""
        self.setup()
        commands = {"run_test": self.run_test,
                    "stop": self.stop,
                    "wait": self.wait}
        while True:
            command, args = self.command_queue.get()
            try:
                rv = commands[command](*args)
            except Exception:
                self.send_message("error",
                                  "Error running command %s with arguments %r:\n%s" %
                                  (command, args, traceback.format_exc()))
            else:
                if rv is Stop:
                    break

    def stop(self):
        return Stop

    def run_test(self, test):
        try:
            return self.executor.run_test(test)
        except Exception:
            self.logger.critical(traceback.format_exc())
            raise

    def wait(self):
        self.executor.wait()
        self.send_message("wait_finished")

    def send_message(self, command, *args):
        self.result_queue.put((command, args))


def start_runner(runner_command_queue, runner_result_queue,
                 executor_cls, executor_kwargs,
                 executor_browser_cls, executor_browser_kwargs,
                 capture_stdio, stop_flag):
    """Launch a TestRunner in a new process"""

    def send_message(command, *args):
        runner_result_queue.put((command, args))

    def handle_error(e):
        logger.critical(traceback.format_exc())
        stop_flag.set()

    logger = MessageLogger(send_message)

    with wptlogging.CaptureIO(logger, capture_stdio):
        try:
            browser = executor_browser_cls(**executor_browser_kwargs)
            executor = executor_cls(browser, **executor_kwargs)
            with TestRunner(logger, runner_command_queue, runner_result_queue, executor) as runner:
                try:
                    runner.run()
                except KeyboardInterrupt:
                    stop_flag.set()
                except Exception as e:
                    handle_error(e)
        except Exception as e:
            handle_error(e)


manager_count = 0


def next_manager_number():
    global manager_count
    local = manager_count = manager_count + 1
    return local


class BrowserManager(object):
    def __init__(self, logger, browser, command_queue, no_timeout=False):
        self.logger = logger
        self.browser = browser
        self.no_timeout = no_timeout
        self.browser_settings = None
        self.last_test = None

        self.started = False

        self.init_timer = None
        self.command_queue = command_queue

    def update_settings(self, test):
        browser_settings = self.browser.settings(test)
        restart_required = ((self.browser_settings is not None and
                             self.browser_settings != browser_settings) or
                            (self.last_test != test and test.expected() == "CRASH"))
        self.browser_settings = browser_settings
        self.last_test = test
        return restart_required

    def init(self, group_metadata):
        """Launch the browser that is being tested,
        and the TestRunner process that will run the tests."""
        # It seems that this lock is helpful to prevent some race that otherwise
        # sometimes stops the spawned processes initialising correctly, and
        # leaves this thread hung
        if self.init_timer is not None:
            self.init_timer.cancel()

        self.logger.debug("Init called, starting browser and runner")

        if not self.no_timeout:
            self.init_timer = threading.Timer(self.browser.init_timeout,
                                              self.init_timeout)
        try:
            if self.init_timer is not None:
                self.init_timer.start()
            self.logger.debug("Starting browser with settings %r" % self.browser_settings)
            self.browser.start(group_metadata=group_metadata, **self.browser_settings)
            self.browser_pid = self.browser.pid()
        except Exception:
            self.logger.warning("Failure during init %s" % traceback.format_exc())
            if self.init_timer is not None:
                self.init_timer.cancel()
            self.logger.error(traceback.format_exc())
            succeeded = False
        else:
            succeeded = True
            self.started = True

        return succeeded

    def send_message(self, command, *args):
        self.command_queue.put((command, args))

    def init_timeout(self):
        # This is called from a separate thread, so we send a message to the
        # main loop so we get back onto the manager thread
        self.logger.debug("init_failed called from timer")
        self.send_message("init_failed")

    def after_init(self):
        """Callback when we have started the browser, started the remote
        control connection, and we are ready to start testing."""
        if self.init_timer is not None:
            self.init_timer.cancel()

    def stop(self, force=False):
        self.browser.stop(force=force)
        self.started = False

    def cleanup(self):
        if self.init_timer is not None:
            self.init_timer.cancel()

    def check_for_crashes(self):
        return self.browser.check_for_crashes()

    def log_crash(self, test_id):
        return self.browser.log_crash(process=self.browser_pid, test=test_id)

    def is_alive(self):
        return self.browser.is_alive()


class _RunnerManagerState(object):
    before_init = namedtuple("before_init", [])
    initializing = namedtuple("initializing_browser",
                              ["test", "test_group", "group_metadata", "failure_count"])
    running = namedtuple("running", ["test", "test_group", "group_metadata"])
    restarting = namedtuple("restarting", ["test", "test_group", "group_metadata"])
    error = namedtuple("error", [])
    stop = namedtuple("stop", [])


RunnerManagerState = _RunnerManagerState()


class TestRunnerManager(threading.Thread):
    def __init__(self, suite_name, test_queue, test_source_cls, browser_cls, browser_kwargs,
                 executor_cls, executor_kwargs, stop_flag, rerun=1, pause_after_test=False,
                 pause_on_unexpected=False, restart_on_unexpected=True, debug_info=None,
                 capture_stdio=True):
        """Thread that owns a single TestRunner process and any processes required
        by the TestRunner (e.g. the Firefox binary).

        TestRunnerManagers are responsible for launching the browser process and the
        runner process, and for logging the test progress. The actual test running
        is done by the TestRunner. In particular they:

        * Start the binary of the program under test
        * Start the TestRunner
        * Tell the TestRunner to start a test, if any
        * Log that the test started
        * Log the test results
        * Take any remedial action required e.g. restart crashed or hung
          processes
        """
        self.suite_name = suite_name

        self.test_source = test_source_cls(test_queue)

        self.browser_cls = browser_cls
        self.browser_kwargs = browser_kwargs

        self.executor_cls = executor_cls
        self.executor_kwargs = executor_kwargs

        # Flags used to shut down this thread if we get a sigint
        self.parent_stop_flag = stop_flag
        self.child_stop_flag = multiprocessing.Event()

        self.rerun = rerun
        self.run_count = 0
        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()

        self.command_queue = Queue()
        self.remote_queue = Queue()

        self.test_runner_proc = None

        threading.Thread.__init__(self, name="TestRunnerManager-%i" % self.manager_number)
        # This is started in the actual new thread
        self.logger = None

        self.test_count = 0
        self.unexpected_count = 0

        # This may not really be what we want
        self.daemon = True

        self.max_restarts = 5

        self.browser = None

        self.capture_stdio = capture_stdio

    def run(self):
        """Main loop for the TestRunnerManager.

        TestRunnerManagers generally receive commands from their
        TestRunner updating them on the status of a test. They
        may also have a stop flag set by the main thread indicating
        that the manager should shut down the next time the event loop
        spins."""
        self.logger = structuredlog.StructuredLogger(self.suite_name)
        with self.browser_cls(self.logger, **self.browser_kwargs) as browser:
            self.browser = BrowserManager(self.logger,
                                          browser,
                                          self.command_queue,
                                          no_timeout=self.debug_info is not None)
            dispatch = {
                RunnerManagerState.before_init: self.start_init,
                RunnerManagerState.initializing: self.init,
                RunnerManagerState.running: self.run_test,
                RunnerManagerState.restarting: self.restart_runner
            }

            self.state = RunnerManagerState.before_init()
            end_states = (RunnerManagerState.stop,
                          RunnerManagerState.error)

            try:
                while not isinstance(self.state, end_states):
                    f = dispatch.get(self.state.__class__)
                    while f:
                        self.logger.debug("Dispatch %s" % f.__name__)
                        if self.should_stop():
                            return
                        new_state = f()
                        if new_state is None:
                            break
                        self.state = new_state
                        self.logger.debug("new state: %s" % self.state.__class__.__name__)
                        if isinstance(self.state, end_states):
                            return
                        f = dispatch.get(self.state.__class__)

                    new_state = None
                    while new_state is None:
                        new_state = self.wait_event()
                        if self.should_stop():
                            return
                    self.state = new_state
                    self.logger.debug("new state: %s" % self.state.__class__.__name__)
            except Exception as e:
                self.logger.error(traceback.format_exc(e))
                raise
            finally:
                self.logger.debug("TestRunnerManager main loop terminating, starting cleanup")
                clean = isinstance(self.state, RunnerManagerState.stop)
                self.stop_runner(force=not clean)
                self.teardown()
        self.logger.debug("TestRunnerManager main loop terminated")

    def wait_event(self):
        dispatch = {
            RunnerManagerState.before_init: {},
            RunnerManagerState.initializing:
            {
                "init_succeeded": self.init_succeeded,
                "init_failed": self.init_failed,
            },
            RunnerManagerState.running:
            {
                "test_ended": self.test_ended,
                "wait_finished": self.wait_finished,
            },
            RunnerManagerState.restarting: {},
            RunnerManagerState.error: {},
            RunnerManagerState.stop: {},
            None: {
                "runner_teardown": self.runner_teardown,
                "log": self.log,
                "error": self.error
            }
        }
        try:
            command, data = self.command_queue.get(True, 1)
            self.logger.debug("Got command: %r" % command)
        except IOError:
            self.logger.error("Got IOError from poll")
            return RunnerManagerState.restarting(0)
        except Empty:
            if (self.debug_info and self.debug_info.interactive and
                self.browser.started and not self.browser.is_alive()):
                self.logger.debug("Debugger exited")
                return RunnerManagerState.stop()

            if (isinstance(self.state, RunnerManagerState.running) and
                not self.test_runner_proc.is_alive()):
                if not self.command_queue.empty():
                    # We got a new message so process that
                    return

                # If we got to here the runner presumably shut down
                # unexpectedly
                self.logger.info("Test runner process shut down")

                if self.state.test is not None:
                    # This could happen if the test runner crashed for some other
                    # reason
                    # Need to consider the unlikely case where one test causes the
                    # runner process to repeatedly die
                    self.logger.critical("Last test did not complete")
                    return RunnerManagerState.error()
                self.logger.warning("More tests found, but runner process died, restarting")
                return RunnerManagerState.restarting(0)
        else:
            f = (dispatch.get(self.state.__class__, {}).get(command) or
                 dispatch.get(None, {}).get(command))
            if not f:
                self.logger.warning("Got command %s in state %s" %
                                    (command, self.state.__class__.__name__))
                return
            return f(*data)

    def should_stop(self):
        return self.child_stop_flag.is_set() or self.parent_stop_flag.is_set()

    def start_init(self):
        test, test_group, group_metadata = self.get_next_test()
        if test is None:
            return RunnerManagerState.stop()
        else:
            return RunnerManagerState.initializing(test, test_group, group_metadata, 0)

    def init(self):
        assert isinstance(self.state, RunnerManagerState.initializing)
        if self.state.failure_count > self.max_restarts:
            self.logger.error("Max restarts exceeded")
            return RunnerManagerState.error()

        self.browser.update_settings(self.state.test)

        result = self.browser.init(self.state.group_metadata)
        if result is Stop:
            return RunnerManagerState.error()
        elif not result:
            return RunnerManagerState.initializing(self.state.test,
                                                   self.state.test_group,
                                                   self.state.group_metadata,
                                                   self.state.failure_count + 1)
        else:
            self.executor_kwargs["group_metadata"] = self.state.group_metadata
            self.start_test_runner()

    def start_test_runner(self):
        # Note that we need to be careful to start the browser before the
        # test runner to ensure that any state set when the browser is started
        # can be passed in to the test runner.
        assert isinstance(self.state, RunnerManagerState.initializing)
        assert self.command_queue is not None
        assert self.remote_queue is not None
        self.logger.info("Starting runner")
        executor_browser_cls, executor_browser_kwargs = self.browser.browser.executor_browser()

        args = (self.remote_queue,
                self.command_queue,
                self.executor_cls,
                self.executor_kwargs,
                executor_browser_cls,
                executor_browser_kwargs,
                self.capture_stdio,
                self.child_stop_flag)
        self.test_runner_proc = Process(target=start_runner,
                                        args=args,
                                        name="TestRunner-%i" % self.manager_number)
        self.test_runner_proc.start()
        self.logger.debug("Test runner started")
        # Now we wait for either an init_succeeded event or an init_failed event

    def init_succeeded(self):
        assert isinstance(self.state, RunnerManagerState.initializing)
        self.browser.after_init()
        return RunnerManagerState.running(self.state.test,
                                          self.state.test_group,
                                          self.state.group_metadata)

    def init_failed(self):
        assert isinstance(self.state, RunnerManagerState.initializing)
        if self.browser.check_for_crashes():
            self.browser.log_crash(None)
        self.browser.after_init()
        self.stop_runner(force=True)
        return RunnerManagerState.initializing(self.state.test,
                                               self.state.test_group,
                                               self.state.group_metadata,
                                               self.state.failure_count + 1)

    def get_next_test(self, test_group=None):
        test = None
        while test is None:
            while test_group is None or len(test_group) == 0:
                test_group, group_metadata = self.test_source.group()
                if test_group is None:
                    self.logger.info("No more tests")
                    return None, None, None
            test = test_group.popleft()
        self.run_count = 0
        return test, test_group, group_metadata

    def run_test(self):
        assert isinstance(self.state, RunnerManagerState.running)
        assert self.state.test is not None

        if self.browser.update_settings(self.state.test):
            self.logger.info("Restarting browser for new test environment")
            return RunnerManagerState.restarting(self.state.test,
                                                 self.state.test_group,
                                                 self.state.group_metadata)

        self.logger.test_start(self.state.test.id)
        if self.rerun > 1:
            self.logger.info("Run %d/%d" % (self.run_count, self.rerun))
        self.run_count += 1
        self.send_message("run_test", self.state.test)

    def test_ended(self, test, results):
        """Handle the end of a test.

        Output the result of each subtest, and the result of the overall
        harness to the logs.
        """
        assert isinstance(self.state, RunnerManagerState.running)
        assert test == self.state.test
        # Write the result of each subtest
        file_result, test_results = results
        subtest_unexpected = False
        for result in test_results:
            if test.disabled(result.name):
                continue
            expected = test.expected(result.name)
            is_unexpected = expected != result.status

            if is_unexpected:
                self.unexpected_count += 1
                self.logger.debug("Unexpected count in this thread %i" % self.unexpected_count)
                subtest_unexpected = True
            self.logger.test_status(test.id,
                                    result.name,
                                    result.status,
                                    message=result.message,
                                    expected=expected,
                                    stack=result.stack)

        # We have a couple of status codes that are used internally, but not exposed to the
        # user. These are used to indicate that some possibly-broken state was reached
        # and we should restart the runner before the next test.
        # INTERNAL-ERROR indicates a Python exception was caught in the harness
        # EXTERNAL-TIMEOUT indicates we had to forcibly kill the browser from the harness
        # because the test didn't return a result after reaching the test-internal timeout
        status_subns = {"INTERNAL-ERROR": "ERROR",
                        "EXTERNAL-TIMEOUT": "TIMEOUT"}
        expected = test.expected()
        status = status_subns.get(file_result.status, file_result.status)

        if self.browser.check_for_crashes():
            status = "CRASH"

        self.test_count += 1
        is_unexpected = expected != status
        if is_unexpected:
            self.unexpected_count += 1
            self.logger.debug("Unexpected count in this thread %i" % self.unexpected_count)
        if status == "CRASH":
            self.browser.log_crash(test.id)

        if "assertion_count" in file_result.extra:
            assertion_count = file_result.extra.pop("assertion_count")
            if assertion_count > 0:
                self.logger.assertion_count(test.id,
                                            int(assertion_count),
                                            test.min_assertion_count,
                                            test.max_assertion_count)

        file_result.extra["test_timeout"] = test.timeout * self.executor_kwargs['timeout_multiplier']

        self.logger.test_end(test.id,
                             status,
                             message=file_result.message,
                             expected=expected,
                             extra=file_result.extra,
                             stack=file_result.stack)

        restart_before_next = (test.restart_after or
                               file_result.status in ("CRASH", "EXTERNAL-TIMEOUT", "INTERNAL-ERROR") or
                               ((subtest_unexpected or is_unexpected) and
                                self.restart_on_unexpected))

        if (not file_result.status == "CRASH" and
            self.pause_after_test or
            (self.pause_on_unexpected and (subtest_unexpected or is_unexpected))):
            self.logger.info("Pausing until the browser exits")
            self.send_message("wait")
        else:
            return self.after_test_end(test, restart_before_next)

    def wait_finished(self):
        assert isinstance(self.state, RunnerManagerState.running)
        self.logger.debug("Wait finished")

        # The browser should be stopped already, but this ensures we do any
        # post-stop processing
        return self.after_test_end(self.state.test, True)

    def after_test_end(self, test, restart):
        assert isinstance(self.state, RunnerManagerState.running)
        if self.run_count == self.rerun:
            test, test_group, group_metadata = self.get_next_test()
            if test is None:
                return RunnerManagerState.stop()
            if test_group != self.state.test_group:
                # We are starting a new group of tests, so force a restart
                restart = True
        else:
            test = test
            test_group = self.state.test_group
            group_metadata = self.state.group_metadata
        if restart:
            return RunnerManagerState.restarting(test, test_group, group_metadata)
        else:
            return RunnerManagerState.running(test, test_group, group_metadata)

    def restart_runner(self):
        """Stop and restart the TestRunner"""
        assert isinstance(self.state, RunnerManagerState.restarting)
        self.stop_runner()
        return RunnerManagerState.initializing(self.state.test, self.state.test_group, self.state.group_metadata, 0)

    def log(self, action, kwargs):
        getattr(self.logger, action)(**kwargs)

    def error(self, message):
        self.logger.error(message)
        self.restart_runner()

    def stop_runner(self, force=False):
        """Stop the TestRunner and the browser binary."""
        if self.test_runner_proc is None:
            return

        if self.test_runner_proc.is_alive():
            self.send_message("stop")
        try:
            self.browser.stop(force=force)
            self.ensure_runner_stopped()
        finally:
            self.cleanup()

    def teardown(self):
        self.logger.debug("TestRunnerManager teardown")
        self.test_runner_proc = None
        self.command_queue.close()
        self.remote_queue.close()
        self.command_queue = None
        self.remote_queue = None

    def ensure_runner_stopped(self):
        self.logger.debug("ensure_runner_stopped")
        if self.test_runner_proc is None:
            return

        self.logger.debug("waiting for runner process to end")
        self.test_runner_proc.join(10)
        self.logger.debug("After join")
        if self.test_runner_proc.is_alive():
            # This might leak a file handle from the queue
            self.logger.warning("Forcibly terminating runner process")
            self.test_runner_proc.terminate()
            self.test_runner_proc.join(10)
        else:
            self.logger.debug("Runner process exited with code %i" % self.test_runner_proc.exitcode)

    def runner_teardown(self):
        self.ensure_runner_stopped()
        return RunnerManagerState.stop()

    def send_message(self, command, *args):
        self.remote_queue.put((command, args))

    def cleanup(self):
        self.logger.debug("TestRunnerManager cleanup")
        if self.browser:
            self.browser.cleanup()
        while True:
            try:
                cmd, data = self.command_queue.get_nowait()
            except Empty:
                break
            else:
                if cmd == "log":
                    self.log(*data)
                elif cmd == "runner_teardown":
                    # It's OK for the "runner_teardown" message to be left in
                    # the queue during cleanup, as we will already have tried
                    # to stop the TestRunner in `stop_runner`.
                    pass
                else:
                    self.logger.warning("Command left in command_queue during cleanup: %r, %r" % (cmd, data))
        while True:
            try:
                cmd, data = self.remote_queue.get_nowait()
                self.logger.warning("Command left in remote_queue during cleanup: %r, %r" % (cmd, data))
            except Empty:
                break


def make_test_queue(tests, test_source_cls, **test_source_kwargs):
    queue = test_source_cls.make_queue(tests, **test_source_kwargs)

    # There is a race condition that means sometimes we continue
    # before the tests have been written to the underlying pipe.
    # Polling the pipe for data here avoids that
    queue._reader.poll(10)
    assert not queue.empty()
    return queue


class ManagerGroup(object):
    def __init__(self, suite_name, size, test_source_cls, test_source_kwargs,
                 browser_cls, browser_kwargs,
                 executor_cls, executor_kwargs,
                 rerun=1,
                 pause_after_test=False,
                 pause_on_unexpected=False,
                 restart_on_unexpected=True,
                 debug_info=None,
                 capture_stdio=True):
        """Main thread object that owns all the TestRunnerManager threads."""
        self.suite_name = suite_name
        self.size = size
        self.test_source_cls = test_source_cls
        self.test_source_kwargs = test_source_kwargs
        self.browser_cls = browser_cls
        self.browser_kwargs = browser_kwargs
        self.executor_cls = executor_cls
        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.rerun = rerun
        self.capture_stdio = capture_stdio

        self.pool = set()
        # Event that is polled by threads so that they can gracefully exit in the face
        # of sigint
        self.stop_flag = threading.Event()
        self.logger = structuredlog.StructuredLogger(suite_name)

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.stop()

    def run(self, test_type, tests):
        """Start all managers in the group"""
        self.logger.debug("Using %i processes" % self.size)
        type_tests = tests[test_type]
        if not type_tests:
            self.logger.info("No %s tests to run" % test_type)
            return

        test_queue = make_test_queue(type_tests, self.test_source_cls, **self.test_source_kwargs)

        for _ in range(self.size):
            manager = TestRunnerManager(self.suite_name,
                                        test_queue,
                                        self.test_source_cls,
                                        self.browser_cls,
                                        self.browser_kwargs,
                                        self.executor_cls,
                                        self.executor_kwargs,
                                        self.stop_flag,
                                        self.rerun,
                                        self.pause_after_test,
                                        self.pause_on_unexpected,
                                        self.restart_on_unexpected,
                                        self.debug_info,
                                        self.capture_stdio)
            manager.start()
            self.pool.add(manager)
        self.wait()

    def is_alive(self):
        """Boolean indicating whether any manager in the group is still alive"""
        return any(manager.is_alive() for manager in self.pool)

    def wait(self):
        """Wait for all the managers in the group to finish"""
        for item in self.pool:
            item.join()

    def stop(self):
        """Set the stop flag so that all managers in the group stop as soon
        as possible"""
        self.stop_flag.set()
        self.logger.debug("Stop flag set in ManagerGroup")

    def test_count(self):
        return sum(item.test_count for item in self.pool)

    def unexpected_count(self):
        return sum(item.unexpected_count for item in self.pool)