diff --git a/azure-pipelines.yml b/azure-pipelines.yml
new file mode 100644
index 000000000..710e42090
--- /dev/null
+++ b/azure-pipelines.yml
@@ -0,0 +1,24 @@
+variables:
+  TOXENV: py
+pool:
+  vmImage: 'windows-latest'
+strategy:
+  matrix:
+    Python35:
+      python.version: '3.5'
+      TOXENV: windows-pinned
+    Python36:
+      python.version: '3.6'
+    Python37:
+      python.version: '3.7'
+    Python38:
+      python.version: '3.8'
+steps:
+- task: UsePythonVersion@0
+  inputs:
+    versionSpec: '$(python.version)'
+  displayName: 'Use Python $(python.version)'
+- script: |
+    pip install -U tox twine wheel codecov
+    tox
+  displayName: 'Run test suite'
diff --git a/scrapy/utils/url.py b/scrapy/utils/url.py
index 955b63d4b..b23ddb459 100644
--- a/scrapy/utils/url.py
+++ b/scrapy/utils/url.py
@@ -83,25 +83,54 @@ def add_http_if_no_scheme(url):
     return url
 
 
+def _is_posix_path(string):
+    return bool(
+        re.match(
+            r'''
+            ^                   # start with...
+            (
+                \.              # ...a single dot,
+                (
+                    \. | [^/\.]+  # optionally followed by
+                )?                # either a second dot or some characters
+                |
+                ~   # $HOME
+            )?      # optional match of ".", ".." or ".blabla"
+            /       # at least one "/" for a file path,
+            .       # and something after the "/"
+            ''',
+            string,
+            flags=re.VERBOSE,
+        )
+    )
+
+
+def _is_windows_path(string):
+    return bool(
+        re.match(
+            r'''
+            ^
+            (
+                [a-z]:\\
+                | \\\\
+            )
+            ''',
+            string,
+            flags=re.IGNORECASE | re.VERBOSE,
+        )
+    )
+
+
+def _is_filesystem_path(string):
+    return _is_posix_path(string) or _is_windows_path(string)
+
+
 def guess_scheme(url):
-    """Add an URL scheme if missing: file:// for filepath-like input or http:// otherwise."""
-    parts = urlparse(url)
-    if parts.scheme:
-        return url
-    # Note: this does not match Windows filepath
-    if re.match(r'''^                   # start with...
-                    (
-                        \.              # ...a single dot,
-                        (
-                            \. | [^/\.]+  # optionally followed by
-                        )?                # either a second dot or some characters
-                    )?      # optional match of ".", ".." or ".blabla"
-                    /       # at least one "/" for a file path,
-                    .       # and something after the "/"
-                    ''', parts.path, flags=re.VERBOSE):
+    """Add an URL scheme if missing: file:// for filepath-like input or
+    http:// otherwise."""
+    if _is_filesystem_path(url):
         return any_to_uri(url)
-    else:
-        return add_http_if_no_scheme(url)
+    return add_http_if_no_scheme(url)
 
 
 def strip_url(url, strip_credentials=True, strip_default_port=True, origin_only=False, strip_fragment=True):
diff --git a/tests/CrawlerRunner/ip_address.py b/tests/CrawlerRunner/ip_address.py
index 826374cd4..3f9738798 100644
--- a/tests/CrawlerRunner/ip_address.py
+++ b/tests/CrawlerRunner/ip_address.py
@@ -1,7 +1,9 @@
 from urllib.parse import urlparse
 
 from twisted.internet import reactor
-from twisted.names.client import createResolver
+from twisted.names import cache, hosts as hostsModule, resolve
+from twisted.names.client import Resolver
+from twisted.python.runtime import platform
 
 from scrapy import Spider, Request
 from scrapy.crawler import CrawlerRunner
@@ -10,6 +12,16 @@ from scrapy.utils.log import configure_logging
 from tests.mockserver import MockServer, MockDNSServer
 
 
+# https://stackoverflow.com/a/32784190
+def createResolver(servers=None, resolvconf=None, hosts=None):
+    if hosts is None:
+        hosts = b'/etc/hosts' if platform.getType() == 'posix' else r'c:\windows\hosts'
+    theResolver = Resolver(resolvconf, servers)
+    hostResolver = hostsModule.Resolver(hosts)
+    chain = [hostResolver, cache.CacheResolver(), theResolver]
+    return resolve.ResolverChain(chain)
+
+
 class LocalhostSpider(Spider):
     name = "localhost_spider"
 
diff --git a/tests/mockserver.py b/tests/mockserver.py
index 30d9bc0e8..1f40473ba 100644
--- a/tests/mockserver.py
+++ b/tests/mockserver.py
@@ -218,9 +218,8 @@ class MockServer:
         self.proc.communicate()
 
     def url(self, path, is_secure=False):
-        host = self.http_address.replace('0.0.0.0', '127.0.0.1')
-        if is_secure:
-            host = self.https_address
+        host = self.https_address if is_secure else self.http_address
+        host = host.replace('0.0.0.0', '127.0.0.1')
         return host + path
 
 
@@ -248,9 +247,8 @@ class MockDNSServer:
     def __enter__(self):
         self.proc = Popen([sys.executable, '-u', '-m', 'tests.mockserver', '-t', 'dns'],
                           stdout=PIPE, env=get_testenv())
-        host, port = self.proc.stdout.readline().strip().decode('ascii').split(":")
-        self.host = host
-        self.port = int(port)
+        self.host = '127.0.0.1'
+        self.port = int(self.proc.stdout.readline().strip().decode('ascii').split(":")[1])
         return self
 
     def __exit__(self, exc_type, exc_value, traceback):
diff --git a/tests/requirements-py3.txt b/tests/requirements-py3.txt
index 0551b1e95..00c56084d 100644
--- a/tests/requirements-py3.txt
+++ b/tests/requirements-py3.txt
@@ -5,10 +5,11 @@ mitmproxy; python_version >= '3.6'
 mitmproxy<4.0.0; python_version < '3.6'
 # https://github.com/pytest-dev/pytest-twisted/issues/93
 pytest != 5.4, != 5.4.1
+pytest-azurepipelines
 pytest-cov
 pytest-twisted >= 1.11
 pytest-xdist
-sybil
+sybil >= 1.3.0  # https://github.com/cjw296/sybil/issues/20#issuecomment-605433422
 testfixtures
 
 # optional for shell wrapper tests
diff --git a/tests/test_command_shell.py b/tests/test_command_shell.py
index 01f164727..66c293c00 100644
--- a/tests/test_command_shell.py
+++ b/tests/test_command_shell.py
@@ -96,7 +96,7 @@ class ShellTest(ProcessTest, SiteTest, unittest.TestCase):
 
     @defer.inlineCallbacks
     def test_local_file(self):
-        filepath = join(tests_datadir, 'test_site/index.html')
+        filepath = join(tests_datadir, 'test_site', 'index.html')
         _, out, _ = yield self.execute([filepath, '-c', 'item'])
         assert b'{}' in out
 
diff --git a/tests/test_commands.py b/tests/test_commands.py
index 002237824..42091ab00 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -2,7 +2,7 @@ import inspect
 import json
 import optparse
 import os
-from stat import S_IWRITE as ANYONE_WRITE_PERMISSION
+import platform
 import subprocess
 import sys
 import tempfile
@@ -11,8 +11,10 @@ from itertools import chain
 from os.path import exists, join, abspath
 from pathlib import Path
 from shutil import rmtree, copytree
+from stat import S_IWRITE as ANYONE_WRITE_PERMISSION
 from tempfile import mkdtemp
 from threading import Timer
+from unittest import skipIf
 
 from twisted.trial import unittest
 
@@ -489,6 +491,9 @@ class BadSpider(scrapy.Spider):
         self.assertIn("start_requests", log)
         self.assertIn("badspider.py", log)
 
+    # https://twistedmatrix.com/trac/ticket/9766
+    @skipIf(platform.system() == 'Windows' and sys.version_info >= (3, 8),
+            "the asyncio reactor is broken on Windows when running Python ≥ 3.8")
     def test_asyncio_enabled_true(self):
         log = self.get_log(self.debug_log_spider, args=[
             '-s', 'TWISTED_REACTOR=twisted.internet.asyncioreactor.AsyncioSelectorReactor'
diff --git a/tests/test_crawler.py b/tests/test_crawler.py
index 038fae323..1a4cfe813 100644
--- a/tests/test_crawler.py
+++ b/tests/test_crawler.py
@@ -1,8 +1,10 @@
 import logging
 import os
+import platform
 import subprocess
 import sys
 import warnings
+from unittest import skipIf
 
 from pytest import raises, mark
 from testfixtures import LogCapture
@@ -251,6 +253,9 @@ class CrawlerRunnerHasSpider(unittest.TestCase):
                 })
 
     @defer.inlineCallbacks
+    # https://twistedmatrix.com/trac/ticket/9766
+    @skipIf(platform.system() == 'Windows' and sys.version_info >= (3, 8),
+            "the asyncio reactor is broken on Windows when running Python ≥ 3.8")
     def test_crawler_process_asyncio_enabled_true(self):
         with LogCapture(level=logging.DEBUG) as log:
             if self.reactor_pytest == 'asyncio':
@@ -292,11 +297,17 @@ class CrawlerProcessSubprocess(ScriptRunnerMixin, unittest.TestCase):
         self.assertIn('Spider closed (finished)', log)
         self.assertNotIn("Using reactor: twisted.internet.asyncioreactor.AsyncioSelectorReactor", log)
 
+    # https://twistedmatrix.com/trac/ticket/9766
+    @skipIf(platform.system() == 'Windows' and sys.version_info >= (3, 8),
+            "the asyncio reactor is broken on Windows when running Python ≥ 3.8")
     def test_asyncio_enabled_no_reactor(self):
         log = self.run_script('asyncio_enabled_no_reactor.py')
         self.assertIn('Spider closed (finished)', log)
         self.assertIn("Using reactor: twisted.internet.asyncioreactor.AsyncioSelectorReactor", log)
 
+    # https://twistedmatrix.com/trac/ticket/9766
+    @skipIf(platform.system() == 'Windows' and sys.version_info >= (3, 8),
+            "the asyncio reactor is broken on Windows when running Python ≥ 3.8")
     def test_asyncio_enabled_reactor(self):
         log = self.run_script('asyncio_enabled_reactor.py')
         self.assertIn('Spider closed (finished)', log)
@@ -320,11 +331,15 @@ class CrawlerProcessSubprocess(ScriptRunnerMixin, unittest.TestCase):
         self.assertIn("Spider closed (finished)", log)
         self.assertIn("Using reactor: twisted.internet.selectreactor.SelectReactor", log)
 
+    @mark.skipif(platform.system() == 'Windows', reason="PollReactor is not supported on Windows")
     def test_reactor_poll(self):
         log = self.run_script("twisted_reactor_poll.py")
         self.assertIn("Spider closed (finished)", log)
         self.assertIn("Using reactor: twisted.internet.pollreactor.PollReactor", log)
 
+    # https://twistedmatrix.com/trac/ticket/9766
+    @skipIf(platform.system() == 'Windows' and sys.version_info >= (3, 8),
+            "the asyncio reactor is broken on Windows when running Python ≥ 3.8")
     def test_reactor_asyncio(self):
         log = self.run_script("twisted_reactor_asyncio.py")
         self.assertIn("Spider closed (finished)", log)
diff --git a/tests/test_feedexport.py b/tests/test_feedexport.py
index e38644214..f7b997560 100644
--- a/tests/test_feedexport.py
+++ b/tests/test_feedexport.py
@@ -455,9 +455,15 @@ class FeedExportTest(unittest.TestCase):
     def run_and_export(self, spider_cls, settings):
         """ Run spider with specified settings; return exported data. """
 
+        def path_to_url(path):
+            return urljoin('file:', pathname2url(str(path)))
+
+        def printf_escape(string):
+            return string.replace('%', '%%')
+
         FEEDS = settings.get('FEEDS') or {}
         settings['FEEDS'] = {
-            urljoin('file:', pathname2url(str(file_path))): feed
+            printf_escape(path_to_url(file_path)): feed
             for file_path, feed in FEEDS.items()
         }
 
diff --git a/tests/test_proxy_connect.py b/tests/test_proxy_connect.py
index eb4ecc91d..fc5658ae7 100644
--- a/tests/test_proxy_connect.py
+++ b/tests/test_proxy_connect.py
@@ -1,5 +1,6 @@
 import json
 import os
+import platform
 import re
 import sys
 from subprocess import Popen, PIPE
@@ -59,6 +60,8 @@ def _wrong_credentials(proxy_url):
 
 @skipIf(sys.version_info < (3, 5, 4),
         "requires mitmproxy < 3.0.0, which these tests do not support")
+@skipIf(platform.system() == 'Windows' and sys.version_info < (3, 7),
+        "mitmproxy does not support Windows when running Python < 3.7")
 class ProxyConnectTestCase(TestCase):
 
     def setUp(self):
diff --git a/tests/test_spiderloader/__init__.py b/tests/test_spiderloader/__init__.py
index d922c6059..4929f1e3e 100644
--- a/tests/test_spiderloader/__init__.py
+++ b/tests/test_spiderloader/__init__.py
@@ -20,13 +20,20 @@ from scrapy.crawler import CrawlerRunner
 module_dir = os.path.dirname(os.path.abspath(__file__))
 
 
+def _copytree(source, target):
+    try:
+        shutil.copytree(source, target)
+    except shutil.Error:
+        pass
+
+
 class SpiderLoaderTest(unittest.TestCase):
 
     def setUp(self):
         orig_spiders_dir = os.path.join(module_dir, 'test_spiders')
         self.tmpdir = tempfile.mkdtemp()
         self.spiders_dir = os.path.join(self.tmpdir, 'test_spiders_xxx')
-        shutil.copytree(orig_spiders_dir, self.spiders_dir)
+        _copytree(orig_spiders_dir, self.spiders_dir)
         sys.path.append(self.tmpdir)
         settings = Settings({'SPIDER_MODULES': ['test_spiders_xxx']})
         self.spider_loader = SpiderLoader.from_settings(settings)
@@ -124,7 +131,7 @@ class DuplicateSpiderNameLoaderTest(unittest.TestCase):
         self.tmpdir = self.mktemp()
         os.mkdir(self.tmpdir)
         self.spiders_dir = os.path.join(self.tmpdir, 'test_spiders_xxx')
-        shutil.copytree(orig_spiders_dir, self.spiders_dir)
+        _copytree(orig_spiders_dir, self.spiders_dir)
         sys.path.append(self.tmpdir)
         self.settings = Settings({'SPIDER_MODULES': ['test_spiders_xxx']})
 
@@ -134,8 +141,8 @@ class DuplicateSpiderNameLoaderTest(unittest.TestCase):
 
     def test_dupename_warning(self):
         # copy 1 spider module so as to have duplicate spider name
-        shutil.copyfile(os.path.join(self.tmpdir, 'test_spiders_xxx/spider3.py'),
-                        os.path.join(self.tmpdir, 'test_spiders_xxx/spider3dupe.py'))
+        shutil.copyfile(os.path.join(self.tmpdir, 'test_spiders_xxx', 'spider3.py'),
+                        os.path.join(self.tmpdir, 'test_spiders_xxx', 'spider3dupe.py'))
 
         with warnings.catch_warnings(record=True) as w:
             spider_loader = SpiderLoader.from_settings(self.settings)
@@ -156,10 +163,10 @@ class DuplicateSpiderNameLoaderTest(unittest.TestCase):
     def test_multiple_dupename_warning(self):
         # copy 2 spider modules so as to have duplicate spider name
         # This should issue 2 warning, 1 for each duplicate spider name
-        shutil.copyfile(os.path.join(self.tmpdir, 'test_spiders_xxx/spider1.py'),
-                        os.path.join(self.tmpdir, 'test_spiders_xxx/spider1dupe.py'))
-        shutil.copyfile(os.path.join(self.tmpdir, 'test_spiders_xxx/spider2.py'),
-                        os.path.join(self.tmpdir, 'test_spiders_xxx/spider2dupe.py'))
+        shutil.copyfile(os.path.join(self.tmpdir, 'test_spiders_xxx', 'spider1.py'),
+                        os.path.join(self.tmpdir, 'test_spiders_xxx', 'spider1dupe.py'))
+        shutil.copyfile(os.path.join(self.tmpdir, 'test_spiders_xxx', 'spider2.py'),
+                        os.path.join(self.tmpdir, 'test_spiders_xxx', 'spider2dupe.py'))
 
         with warnings.catch_warnings(record=True) as w:
             spider_loader = SpiderLoader.from_settings(self.settings)
diff --git a/tests/test_utils_asyncio.py b/tests/test_utils_asyncio.py
index 295323e4d..a2114bd18 100644
--- a/tests/test_utils_asyncio.py
+++ b/tests/test_utils_asyncio.py
@@ -1,4 +1,6 @@
-from unittest import TestCase
+import platform
+import sys
+from unittest import skipIf, TestCase
 
 from pytest import mark
 
@@ -12,6 +14,9 @@ class AsyncioTest(TestCase):
         # the result should depend only on the pytest --reactor argument
         self.assertEqual(is_asyncio_reactor_installed(), self.reactor_pytest == 'asyncio')
 
+    # https://twistedmatrix.com/trac/ticket/9766
+    @skipIf(platform.system() == 'Windows' and sys.version_info >= (3, 8),
+            "the asyncio reactor is broken on Windows when running Python ≥ 3.8")
     def test_install_asyncio_reactor(self):
         # this should do nothing
         install_reactor("twisted.internet.asyncioreactor.AsyncioSelectorReactor")
diff --git a/tests/test_utils_iterators.py b/tests/test_utils_iterators.py
index 3ebe3ac24..d17bb2cbc 100644
--- a/tests/test_utils_iterators.py
+++ b/tests/test_utils_iterators.py
@@ -7,7 +7,7 @@ from scrapy.http import XmlResponse, TextResponse, Response
 from tests import get_testdata
 
 
-FOOBAR_NL = u"foo\nbar"
+FOOBAR_NL = "foo{}bar".format(os.linesep)
 
 
 class XmliterTestCase(unittest.TestCase):
diff --git a/tests/test_utils_trackref.py b/tests/test_utils_trackref.py
index 16e02f919..b8e8c3130 100644
--- a/tests/test_utils_trackref.py
+++ b/tests/test_utils_trackref.py
@@ -1,7 +1,10 @@
 import unittest
 from io import StringIO
+from time import sleep, time
 from unittest import mock
 
+from twisted.trial.unittest import SkipTest
+
 from scrapy.utils import trackref
 
 
@@ -55,7 +58,18 @@ Foo                                 1   oldest: 0s ago\n\n''')
 
     def test_get_oldest(self):
         o1 = Foo()  # NOQA
+
+        o1_time = time()
+
         o2 = Bar()  # NOQA
+
+        o3_time = time()
+        if o3_time <= o1_time:
+            sleep(0.01)
+            o3_time = time()
+        if o3_time <= o1_time:
+            raise SkipTest('time.time is not precise enough')
+
         o3 = Foo()  # NOQA
         self.assertIs(trackref.get_oldest('Foo'), o1)
         self.assertIs(trackref.get_oldest('Bar'), o2)
diff --git a/tests/test_utils_url.py b/tests/test_utils_url.py
index a194a0998..2f885a0e8 100644
--- a/tests/test_utils_url.py
+++ b/tests/test_utils_url.py
@@ -1,8 +1,14 @@
 import unittest
 
 from scrapy.spiders import Spider
-from scrapy.utils.url import (url_is_from_any_domain, url_is_from_spider,
-                              add_http_if_no_scheme, guess_scheme, strip_url)
+from scrapy.utils.url import (
+    add_http_if_no_scheme,
+    guess_scheme,
+    _is_filesystem_path,
+    strip_url,
+    url_is_from_any_domain,
+    url_is_from_spider,
+)
 
 
 __doctests__ = ['scrapy.utils.url']
@@ -433,5 +439,28 @@ class StripUrl(unittest.TestCase):
             self.assertEqual(strip_url(i, origin_only=True), o)
 
 
+class IsPathTestCase(unittest.TestCase):
+
+    def test_path(self):
+        for input_value, output_value in (
+            # https://en.wikipedia.org/wiki/Path_(computing)#Representations_of_paths_by_operating_system_and_shell
+            # Unix-like OS, Microsoft Windows / cmd.exe
+            ("/home/user/docs/Letter.txt", True),
+            ("./inthisdir", True),
+            ("../../greatgrandparent", True),
+            ("~/.rcinfo", True),
+            (r"C:\user\docs\Letter.txt", True),
+            ("/user/docs/Letter.txt", True),
+            (r"C:\Letter.txt", True),
+            (r"\\Server01\user\docs\Letter.txt", True),
+            (r"\\?\UNC\Server01\user\docs\Letter.txt", True),
+            (r"\\?\C:\user\docs\Letter.txt", True),
+            (r"C:\user\docs\somefile.ext:alternate_stream_name", True),
+
+            (r"https://example.com", False),
+        ):
+            self.assertEqual(_is_filesystem_path(input_value), output_value, input_value)
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/tox.ini b/tox.ini
index 27d21ade2..f729327ca 100644
--- a/tox.ini
+++ b/tox.ini
@@ -63,14 +63,12 @@ basepython = pypy3
 commands =
     py.test {posargs:--durations=10 docs scrapy tests}
 
-[testenv:pinned]
-basepython = python3
+[pinned]
 deps =
     -ctests/constraints.txt
     cryptography==2.0
     cssselect==0.9.1
     itemadapter==0.1.0
-    lxml==3.5.0
     parsel==1.5.0
     Protego==0.1.15
     PyDispatcher==2.0.5
@@ -85,6 +83,20 @@ deps =
     botocore==1.3.23
     Pillow==3.4.2
 
+[testenv:pinned]
+basepython = python3
+deps =
+    {[pinned]deps}
+    lxml==3.5.0
+
+[testenv:windows-pinned]
+basepython = python3
+deps =
+    {[pinned]deps}
+    # First lxml version that includes a Windows wheel for Python 3.5, so we do
+    # not need to build lxml from sources in a CI Windows job:
+    lxml==3.8.0
+
 [testenv:extra-deps]
 deps =
     {[testenv]deps}