BUILD_FAILURE = auto()
        TEST_FAILURE = auto()
 
-def get_kernel_root_path():
-       parts = sys.argv[0] if not __file__ else __file__
-       parts = os.path.realpath(parts).split('tools/testing/kunit')
+def get_kernel_root_path() -> str:
+       path = sys.argv[0] if not __file__ else __file__
+       parts = os.path.realpath(path).split('tools/testing/kunit')
        if len(parts) != 2:
                sys.exit(1)
        return parts[0]
                                exec_result.elapsed_time))
        return parse_result
 
-def add_common_opts(parser):
+def add_common_opts(parser) -> None:
        parser.add_argument('--build_dir',
                            help='As in the make command, it specifies the build '
                            'directory.',
                            help='Run all KUnit tests through allyesconfig',
                            action='store_true')
 
-def add_build_opts(parser):
+def add_build_opts(parser) -> None:
        parser.add_argument('--jobs',
                            help='As in the make command, "Specifies  the number of '
                            'jobs (commands) to run simultaneously."',
                            type=int, default=8, metavar='jobs')
 
-def add_exec_opts(parser):
+def add_exec_opts(parser) -> None:
        parser.add_argument('--timeout',
                            help='maximum number of seconds to allow for all tests '
                            'to run. This does not include time taken to build the '
                            default=300,
                            metavar='timeout')
 
-def add_parse_opts(parser):
+def add_parse_opts(parser) -> None:
        parser.add_argument('--raw_output', help='don\'t format output from kernel',
                            action='store_true')
        parser.add_argument('--json',
 
 import os
 import shutil
 import signal
+from typing import Iterator
 
 from contextlib import ExitStack
 
 class LinuxSourceTreeOperations(object):
        """An abstraction over command line operations performed on a source tree."""
 
-       def make_mrproper(self):
+       def make_mrproper(self) -> None:
                try:
                        subprocess.check_output(['make', 'mrproper'], stderr=subprocess.STDOUT)
                except OSError as e:
                except subprocess.CalledProcessError as e:
                        raise ConfigError(e.output.decode())
 
-       def make_olddefconfig(self, build_dir, make_options):
+       def make_olddefconfig(self, build_dir, make_options) -> None:
                command = ['make', 'ARCH=um', 'olddefconfig']
                if make_options:
                        command.extend(make_options)
                except subprocess.CalledProcessError as e:
                        raise ConfigError(e.output.decode())
 
-       def make_allyesconfig(self, build_dir, make_options):
+       def make_allyesconfig(self, build_dir, make_options) -> None:
                kunit_parser.print_with_timestamp(
                        'Enabling all CONFIGs for UML...')
                command = ['make', 'ARCH=um', 'allyesconfig']
                kunit_parser.print_with_timestamp(
                        'Starting Kernel with all configs takes a few minutes...')
 
-       def make(self, jobs, build_dir, make_options):
+       def make(self, jobs, build_dir, make_options) -> None:
                command = ['make', 'ARCH=um', '--jobs=' + str(jobs)]
                if make_options:
                        command.extend(make_options)
                if stderr:  # likely only due to build warnings
                        print(stderr.decode())
 
-       def linux_bin(self, params, timeout, build_dir):
+       def linux_bin(self, params, timeout, build_dir) -> None:
                """Runs the Linux UML binary. Must be named 'linux'."""
                linux_bin = get_file_path(build_dir, 'linux')
                outfile = get_outfile_path(build_dir)
                                                   stderr=subprocess.STDOUT)
                        process.wait(timeout)
 
-def get_kconfig_path(build_dir):
+def get_kconfig_path(build_dir) -> str:
        return get_file_path(build_dir, KCONFIG_PATH)
 
-def get_kunitconfig_path(build_dir):
+def get_kunitconfig_path(build_dir) -> str:
        return get_file_path(build_dir, KUNITCONFIG_PATH)
 
-def get_outfile_path(build_dir):
+def get_outfile_path(build_dir) -> str:
        return get_file_path(build_dir, OUTFILE_PATH)
 
 class LinuxSourceTree(object):
        """Represents a Linux kernel source tree with KUnit tests."""
 
-       def __init__(self):
+       def __init__(self) -> None:
                self._ops = LinuxSourceTreeOperations()
                signal.signal(signal.SIGINT, self.signal_handler)
 
-       def clean(self):
+       def clean(self) -> bool:
                try:
                        self._ops.make_mrproper()
                except ConfigError as e:
                        return False
                return True
 
-       def create_kunitconfig(self, build_dir, defconfig=DEFAULT_KUNITCONFIG_PATH):
+       def create_kunitconfig(self, build_dir, defconfig=DEFAULT_KUNITCONFIG_PATH) -> None:
                kunitconfig_path = get_kunitconfig_path(build_dir)
                if not os.path.exists(kunitconfig_path):
                        shutil.copyfile(defconfig, kunitconfig_path)
 
-       def read_kunitconfig(self, build_dir):
+       def read_kunitconfig(self, build_dir) -> None:
                kunitconfig_path = get_kunitconfig_path(build_dir)
                self._kconfig = kunit_config.Kconfig()
                self._kconfig.read_from_file(kunitconfig_path)
 
-       def validate_config(self, build_dir):
+       def validate_config(self, build_dir) -> bool:
                kconfig_path = get_kconfig_path(build_dir)
                validated_kconfig = kunit_config.Kconfig()
                validated_kconfig.read_from_file(kconfig_path)
                        return False
                return True
 
-       def build_config(self, build_dir, make_options):
+       def build_config(self, build_dir, make_options) -> bool:
                kconfig_path = get_kconfig_path(build_dir)
                if build_dir and not os.path.exists(build_dir):
                        os.mkdir(build_dir)
                        return False
                return self.validate_config(build_dir)
 
-       def build_reconfig(self, build_dir, make_options):
+       def build_reconfig(self, build_dir, make_options) -> bool:
                """Creates a new .config if it is not a subset of the .kunitconfig."""
                kconfig_path = get_kconfig_path(build_dir)
                if os.path.exists(kconfig_path):
                        print('Generating .config ...')
                        return self.build_config(build_dir, make_options)
 
-       def build_um_kernel(self, alltests, jobs, build_dir, make_options):
+       def build_um_kernel(self, alltests, jobs, build_dir, make_options) -> bool:
                try:
                        if alltests:
                                self._ops.make_allyesconfig(build_dir, make_options)
                        return False
                return self.validate_config(build_dir)
 
-       def run_kernel(self, args=[], build_dir='', timeout=None):
+       def run_kernel(self, args=[], build_dir='', timeout=None) -> Iterator[str]:
                args.extend(['mem=1G', 'console=tty'])
                self._ops.linux_bin(args, timeout, build_dir)
                outfile = get_outfile_path(build_dir)
                        for line in file:
                                yield line
 
-       def signal_handler(self, sig, frame):
+       def signal_handler(self, sig, frame) -> None:
                logging.error('Build interruption occurred. Cleaning console.')
                subprocess.call(['stty', 'sane'])
 
 from datetime import datetime
 from enum import Enum, auto
 from functools import reduce
-from typing import List, Optional, Tuple
+from typing import Iterator, List, Optional, Tuple
 
 TestResult = namedtuple('TestResult', ['status','suites','log'])
 
 class TestSuite(object):
-       def __init__(self):
-               self.status = None
-               self.name = None
-               self.cases = []
+       def __init__(self) -> None:
+               self.status = None  # type: Optional[TestStatus]
+               self.name = ''
+               self.cases = []  # type: List[TestCase]
 
-       def __str__(self):
-               return 'TestSuite(' + self.status + ',' + self.name + ',' + str(self.cases) + ')'
+       def __str__(self) -> str:
+               return 'TestSuite(' + str(self.status) + ',' + self.name + ',' + str(self.cases) + ')'
 
-       def __repr__(self):
+       def __repr__(self) -> str:
                return str(self)
 
 class TestCase(object):
-       def __init__(self):
-               self.status = None
+       def __init__(self) -> None:
+               self.status = None  # type: Optional[TestStatus]
                self.name = ''
-               self.log = []
+               self.log = []  # type: List[str]
 
-       def __str__(self):
-               return 'TestCase(' + self.status + ',' + self.name + ',' + str(self.log) + ')'
+       def __str__(self) -> str:
+               return 'TestCase(' + str(self.status) + ',' + self.name + ',' + str(self.log) + ')'
 
-       def __repr__(self):
+       def __repr__(self) -> str:
                return str(self)
 
 class TestStatus(Enum):
 kunit_end_re = re.compile('(List of all partitions:|'
                          'Kernel panic - not syncing: VFS:)')
 
-def isolate_kunit_output(kernel_output):
+def isolate_kunit_output(kernel_output) -> Iterator[str]:
        started = False
        for line in kernel_output:
                line = line.rstrip()  # line always has a trailing \n
                elif started:
                        yield line[prefix_len:] if prefix_len > 0 else line
 
-def raw_output(kernel_output):
+def raw_output(kernel_output) -> None:
        for line in kernel_output:
                print(line.rstrip())
 
 
 RESET = '\033[0;0m'
 
-def red(text):
+def red(text) -> str:
        return '\033[1;31m' + text + RESET
 
-def yellow(text):
+def yellow(text) -> str:
        return '\033[1;33m' + text + RESET
 
-def green(text):
+def green(text) -> str:
        return '\033[1;32m' + text + RESET
 
-def print_with_timestamp(message):
+def print_with_timestamp(message) -> None:
        print('[%s] %s' % (datetime.now().strftime('%H:%M:%S'), message))
 
-def format_suite_divider(message):
+def format_suite_divider(message) -> str:
        return '======== ' + message + ' ========'
 
-def print_suite_divider(message):
+def print_suite_divider(message) -> None:
        print_with_timestamp(DIVIDER)
        print_with_timestamp(format_suite_divider(message))
 
-def print_log(log):
+def print_log(log) -> None:
        for m in log:
                print_with_timestamp(m)