diff --git a/.travis.yml b/.travis.yml
index 0cc37dd..61a4e33 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,17 +1,15 @@
 sudo: false
 language: python
 python:
-  - "3.4"
   - "3.5"
   - "3.6"
   - "nightly"
   # ptr requires Python >= 3.3 but pypy3 reports 3.2
   # - "pypy3"
-install: pip install -U pytest pytest-runner
-script: python setup.py pytest
+install: pip install -U aiohttp pytest pytest-asyncio pytest-xdist flaky
+script: pytest
 env:
   global:
-    - ASYNC_TEST_TIMEOUT=20
     # github
     - secure: "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"
     # gitlab
diff --git a/README.rst b/README.rst
index bd68995..1d04e46 100644
--- a/README.rst
+++ b/README.rst
@@ -45,9 +45,8 @@ Contents
 
 Dependency
 ==========
-- Python 3
-- Tornado
-- Optional pycurl
+- Python 3.5+
+- aiohttp
 - All commands used in your version source files
 
 Running
@@ -132,7 +131,7 @@ regex
   When multiple version strings are found, the maximum of those is chosen.
 
 proxy
-  The HTTP proxy to use. The format is ``host:port``, e.g. ``localhost:8087``. This requires `pycurl <http://pycurl.sourceforge.net/>`_.
+  The HTTP proxy to use. The format is ``host:port``, e.g. ``localhost:8087``.
 
 user_agent
   The ``User-Agent`` header value to use. Use something more like a tool (e.g. ``curl/7.40.0``) in Europe or the real web page won't get through because cookie policies (SourceForge has this issue).
@@ -191,7 +190,7 @@ sort_version_key
   ``pkg_resources.parse_version``. ``vercmp`` use ``pyalpm.vercmp``.
 
 proxy
-  The HTTP proxy to use. The format is ``host:port``, e.g. ``localhost:8087``. This requires `pycurl <http://pycurl.sourceforge.net/>`_.
+  The HTTP proxy to use. The format is ``host:port``, e.g. ``localhost:8087``.
 
 An environment variable ``NVCHECKER_GITHUB_TOKEN`` can be set to a GitHub OAuth token in order to request more frequently than anonymously.
 
@@ -289,7 +288,7 @@ cpan
   The name used on CPAN, e.g. ``YAML``.
 
 proxy
-  The HTTP proxy to use. The format is ``host:port``, e.g. ``localhost:8087``. This requires `pycurl <http://pycurl.sourceforge.net/>`_.
+  The HTTP proxy to use. The format is ``host:port``, e.g. ``localhost:8087``.
 
 Check Packagist
 ---------------
diff --git a/nvchecker/__init__.py b/nvchecker/__init__.py
index c67cccf..a08bbe8 100644
--- a/nvchecker/__init__.py
+++ b/nvchecker/__init__.py
@@ -1,4 +1,4 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-__version__ = '0.4.5dev'
+__version__ = '0.5dev'
diff --git a/nvchecker/core.py b/nvchecker/core.py
index 8644d84..a3af337 100644
--- a/nvchecker/core.py
+++ b/nvchecker/core.py
@@ -6,11 +6,11 @@ import os
 import sys
 import logging
 import configparser
-
-from tornado.stack_context import ExceptionStackContext
+import asyncio
 
 from .lib import nicelogger
 from .get_version import get_version
+from .source import session
 
 from . import __version__
 
@@ -60,9 +60,8 @@ def write_verfile(file, versions):
   safe_overwrite(file, data, method='writelines')
 
 class Source:
-  started = False
-  tasks = 0
   oldver = newver = None
+
   def __init__(self, file):
     self.config = config = configparser.ConfigParser(
       dict_type=dict, allow_no_value=True
@@ -72,62 +71,51 @@ class Source:
     if '__config__' in config:
       c = config['__config__']
       d = os.path.dirname(file.name)
-      self.oldver = os.path.expandvars(os.path.expanduser(os.path.join(d, c.get('oldver'))))
-      self.newver = os.path.expandvars(os.path.expanduser(os.path.join(d, c.get('newver'))))
+      self.oldver = os.path.expandvars(os.path.expanduser(
+        os.path.join(d, c.get('oldver'))))
+      self.newver = os.path.expandvars(os.path.expanduser(
+        os.path.join(d, c.get('newver'))))
 
-  def check(self):
-    self.started = True
+      session.nv_config = config["__config__"]
 
+  async def check(self):
     if self.oldver:
       self.oldvers = read_verfile(self.oldver)
     else:
       self.oldvers = {}
     self.curvers = self.oldvers.copy()
 
+    futures = []
     config = self.config
     for name in config.sections():
       if name == '__config__':
         continue
-      self.task_inc()
       conf = config[name]
       conf['oldver'] = self.oldvers.get(name, None)
-      with ExceptionStackContext(self._handle_exception):
-        get_version(name, conf, self.print_version_update)
+      futures.append(get_version(name, conf))
 
-  def _handle_exception(self, type, value, traceback):
-    self.task_dec()
-    raise value.with_traceback(traceback)
+    for fu in asyncio.as_completed(futures):
+      try:
+        name, version = await fu
+        if version is not None:
+          self.print_version_update(name, version)
+      except Exception:
+        logger.exception('error happened dealing with %s', name)
 
-  def task_inc(self):
-    self.tasks += 1
-
-  def task_dec(self):
-    self.tasks -= 1
-    if self.tasks == 0 and self.started:
-      if self.newver:
-        write_verfile(self.newver, self.curvers)
-      self.on_finish()
+    if self.newver:
+      write_verfile(self.newver, self.curvers)
 
   def print_version_update(self, name, version):
-    try:
-      if version is None:
-        return
-
-      oldver = self.oldvers.get(name, None)
-      if not oldver or oldver != version:
-        logger.info('%s updated version %s', name, version)
-        self.curvers[name] = version
-        self.on_update(name, version, oldver)
-      else:
-        logger.debug('%s current version %s', name, version)
-    finally:
-      self.task_dec()
+    oldver = self.oldvers.get(name, None)
+    if not oldver or oldver != version:
+      logger.info('%s updated to %s', name, version)
+      self.curvers[name] = version
+      self.on_update(name, version, oldver)
+    else:
+      logger.debug('%s current %s', name, version)
 
   def on_update(self, name, version, oldver):
     pass
 
-  def on_finish(self):
-    pass
-
   def __repr__(self):
     return '<Source from %r>' % self.name
diff --git a/nvchecker/get_version.py b/nvchecker/get_version.py
index 666ab69..1b60b56 100644
--- a/nvchecker/get_version.py
+++ b/nvchecker/get_version.py
@@ -11,12 +11,11 @@ handler_precedence = (
   'cratesio', 'npm', 'hackage', 'cpan', 'gitlab', 'packagist'
 )
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   for key in handler_precedence:
     if key in conf:
       func = import_module('.source.' + key, __package__).get_version
-      func(name, conf, callback)
-      break
+      return await func(name, conf)
   else:
     logger.error('%s: no idea to get version info.', name)
-    callback(name, None)
+    return name, None
diff --git a/nvchecker/main.py b/nvchecker/main.py
index 6a0ba39..b1a8041 100755
--- a/nvchecker/main.py
+++ b/nvchecker/main.py
@@ -5,7 +5,7 @@
 import logging
 import argparse
 
-from tornado.ioloop import IOLoop
+import asyncio
 
 from .lib import notify
 from . import core
@@ -21,9 +21,6 @@ class Source(core.Source):
       notifications.append(msg)
       notify.update('nvchecker', '\n'.join(notifications))
 
-  def on_finish(self):
-    IOLoop.instance().stop()
-
 def main():
   global args
 
@@ -37,11 +34,11 @@ def main():
 
   if not args.file:
     return
+
   s = Source(args.file)
 
-  ioloop = IOLoop.instance()
-  ioloop.add_callback(s.check)
-  ioloop.start()
+  ioloop = asyncio.get_event_loop()
+  ioloop.run_until_complete(s.check())
 
 if __name__ == '__main__':
   main()
diff --git a/nvchecker/source/__init__.py b/nvchecker/source/__init__.py
index 780a732..fa45a66 100644
--- a/nvchecker/source/__init__.py
+++ b/nvchecker/source/__init__.py
@@ -1,4 +1,18 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from .base import *
+import atexit
+import aiohttp
+connector = aiohttp.TCPConnector(limit=20)
+
+config = None
+
+class BetterClientSession(aiohttp.ClientSession):
+    async def _request(self, *args, **kwargs):
+        if hasattr(self, "nv_config") and self.nv_config.get("proxy"):
+            kwargs.setdefault("proxy", self.nv_config.get("proxy"))
+
+        return await super(BetterClientSession, self)._request(*args, **kwargs)
+
+session = BetterClientSession(connector=connector, read_timeout=10, conn_timeout=5)
+atexit.register(session.close)
diff --git a/nvchecker/source/archpkg.py b/nvchecker/source/archpkg.py
index 9c1019c..15f8775 100644
--- a/nvchecker/source/archpkg.py
+++ b/nvchecker/source/archpkg.py
@@ -1,33 +1,22 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from functools import partial
 import logging
-import json
-
-from tornado.httpclient import AsyncHTTPClient
+from . import session
 
 logger = logging.getLogger(__name__)
 
-URL = 'https://www.archlinux.org/packages/search/json/?name='
+URL = 'https://www.archlinux.org/packages/search/json/'
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   pkg = conf.get('archpkg') or name
   strip_release = conf.getboolean('strip-release', False)
-  url = URL + pkg
-  AsyncHTTPClient().fetch(
-    url, partial(_pkg_done, name, strip_release, callback))
-
-def _pkg_done(name, strip_release, callback, res):
-  if res.error:
-    raise res.error
-
-  data = json.loads(res.body.decode('utf-8'))
+  async with session.get(URL, params={"name": pkg}) as res:
+    data = await res.json()
 
   if not data['results']:
     logger.error('Arch package not found: %s', name)
-    callback(name, None)
-    return
+    return name, None
 
   r = [r for r in data['results'] if r['repo'] != 'testing'][0]
   if strip_release:
@@ -35,4 +24,4 @@ def _pkg_done(name, strip_release, callback, res):
   else:
     version = r['pkgver'] + '-' + r['pkgrel']
 
-  callback(name, version)
+  return name, version
diff --git a/nvchecker/source/aur.py b/nvchecker/source/aur.py
index 50a650c..5327b33 100644
--- a/nvchecker/source/aur.py
+++ b/nvchecker/source/aur.py
@@ -1,36 +1,24 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from functools import partial
-import json
 import logging
-
-from tornado.httpclient import AsyncHTTPClient
-from tornado.escape import url_escape
+from . import session
 
 AUR_URL = 'https://aur.archlinux.org/rpc/?v=5&type=info&arg[]='
 
 logger = logging.getLogger(__name__)
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   aurname = conf.get('aur') or name
   strip_release = conf.getboolean('strip-release', False)
-  url = AUR_URL + url_escape(aurname)
-  AsyncHTTPClient().fetch(
-    url, partial(_aur_done, name, strip_release, callback))
-
-def _aur_done(name, strip_release, callback, res):
-  if res.error:
-    raise res.error
-
-  data = json.loads(res.body.decode('utf-8'))
+  async with session.get(AUR_URL, params={"v": 5, "type": "info", "arg[]": aurname}) as res:
+    data = await res.json()
 
   if not data['results']:
     logger.error('AUR upstream not found for %s', name)
-    callback(name, None)
-    return
+    return name, None
 
   version = data['results'][0]['Version']
   if strip_release and '-' in version:
     version = version.rsplit('-', 1)[0]
-  callback(name, version)
+  return name, version
diff --git a/nvchecker/source/base.py b/nvchecker/source/base.py
deleted file mode 100644
index 968f103..0000000
--- a/nvchecker/source/base.py
+++ /dev/null
@@ -1,10 +0,0 @@
-# MIT licensed
-# Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
-
-from tornado.httpclient import AsyncHTTPClient
-try:
-  import pycurl
-  AsyncHTTPClient.configure("tornado.curl_httpclient.CurlAsyncHTTPClient")
-except ImportError:
-  pycurl = None
-
diff --git a/nvchecker/source/bitbucket.py b/nvchecker/source/bitbucket.py
index 148dbe7..b6b831d 100644
--- a/nvchecker/source/bitbucket.py
+++ b/nvchecker/source/bitbucket.py
@@ -1,11 +1,7 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-import os
-import json
-from functools import partial
-
-from tornado.httpclient import AsyncHTTPClient, HTTPRequest
+from aiohttp import request
 
 from ..sortversion import sort_version_keys
 
@@ -13,7 +9,7 @@ from ..sortversion import sort_version_keys
 BITBUCKET_URL = 'https://bitbucket.org/api/2.0/repositories/%s/commits/%s'
 BITBUCKET_MAX_TAG = 'https://bitbucket.org/api/1.0/repositories/%s/tags'
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   repo = conf.get('bitbucket')
   br = conf.get('branch', '')
   use_max_tag = conf.getboolean('use_max_tag', False)
@@ -23,16 +19,12 @@ def get_version(name, conf, callback):
     url = BITBUCKET_MAX_TAG % repo
   else:
     url = BITBUCKET_URL % (repo, br)
-  request = HTTPRequest(url, user_agent='lilydjwg/nvchecker')
-  AsyncHTTPClient().fetch(request,
-                          callback=partial(_bitbucket_done, name, use_max_tag, ignored_tags, sort_version_key, callback))
-
-def _bitbucket_done(name, use_max_tag, ignored_tags, sort_version_key, callback, res):
-  data = json.loads(res.body.decode('utf-8'))
+  async with request("GET", url) as res:
+    data = await res.json()
   if use_max_tag:
     data = [tag for tag in data if tag not in ignored_tags]
     data.sort(key=sort_version_key)
     version = data[-1]
   else:
     version = data['values'][0]['date'].split('T', 1)[0].replace('-', '')
-  callback(name, version)
+  return name, version
diff --git a/nvchecker/source/cmd.py b/nvchecker/source/cmd.py
index 260e70c..d7c3954 100644
--- a/nvchecker/source/cmd.py
+++ b/nvchecker/source/cmd.py
@@ -1,44 +1,18 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-import queue
 import logging
-from functools import partial
-
-import tornado.process
-from tornado.ioloop import IOLoop
+import asyncio
 
 logger = logging.getLogger(__name__)
-cmd_q = queue.Queue()
-cmd_q.running = False
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   cmd = conf['cmd']
-  cmd_q.put((name, cmd, callback))
-  if not cmd_q.running:
-    _run_command()
+  p = await asyncio.create_subprocess_shell(cmd, stdout=asyncio.subprocess.PIPE)
 
-def _run_command():
-  cmd_q.running = True
-  try:
-    name, cmd, callback = cmd_q.get_nowait()
-  except queue.Empty:
-    cmd_q.running = False
-    return
-
-  p = tornado.process.Subprocess(cmd, shell=True,
-                                 stdout=tornado.process.Subprocess.STREAM)
-  p.set_exit_callback(partial(_command_done, name, callback, p))
-
-def _command_done(name, callback, process, status):
-  if status != 0:
-    logger.error('%s: command exited with %d.', name, status)
-    callback(name, None)
-  else:
-    process.stdout.read_until_close(partial(_got_version_from_cmd, callback, name))
-  _run_command()
-
-def _got_version_from_cmd(callback, name, output):
-  output = output.strip().decode('latin1')
-  callback(name, output)
+  output = (await p.communicate())[0].strip().decode('latin1')
+  if p.returncode != 0:
+    logger.error('%s: command exited with %d.', name, p.returncode)
+    return name, None
 
+  return name, output
diff --git a/nvchecker/source/cratesio.py b/nvchecker/source/cratesio.py
index 46d328a..19ffceb 100644
--- a/nvchecker/source/cratesio.py
+++ b/nvchecker/source/cratesio.py
@@ -2,24 +2,13 @@
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
 import os
-import json
-from functools import partial
-
-from tornado.httpclient import AsyncHTTPClient, HTTPRequest
-
-from ..sortversion import sort_version_keys
+from . import session
 
 API_URL = 'https://crates.io/api/v1/crates/%s'
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   name = conf.get('cratesio') or name
-  request = HTTPRequest(API_URL % name, user_agent='lilydjwg/nvchecker')
-  AsyncHTTPClient().fetch(
-    request,
-    callback = partial(_cratesio_done, name, callback),
-  )
-
-def _cratesio_done(name, callback, res):
-  data = json.loads(res.body.decode('utf-8'))
+  async with session.get(API_URL % name) as res:
+    data = await res.json()
   version = [v['num'] for v in data['versions'] if not v['yanked']][0]
-  callback(name, version)
+  return name, version
diff --git a/nvchecker/source/debianpkg.py b/nvchecker/source/debianpkg.py
index ac4d15c..3d03e63 100644
--- a/nvchecker/source/debianpkg.py
+++ b/nvchecker/source/debianpkg.py
@@ -1,34 +1,24 @@
 # MIT licensed
 # Copyright (c) 2017 Felix Yan <felixonmars@archlinux.org>, et al.
 
-from functools import partial
 import logging
-import json
-
-from tornado.httpclient import AsyncHTTPClient
+from . import session
 
 logger = logging.getLogger(__name__)
 
 URL = 'https://sources.debian.net/api/src/%(pkgname)s/?suite=%(suite)s'
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   pkg = conf.get('debianpkg') or name
   strip_release = conf.getboolean('strip-release', False)
   suite = conf.get('suite') or "sid"
   url = URL % {"pkgname": pkg, "suite": suite}
-  AsyncHTTPClient().fetch(
-    url, partial(_pkg_done, name, strip_release, callback))
-
-def _pkg_done(name, strip_release, callback, res):
-  if res.error:
-    raise res.error
-
-  data = json.loads(res.body.decode('utf-8'))
+  async with session.get(url) as res:
+    data = await res.json()
 
   if not data.get('versions'):
     logger.error('Debian package not found: %s', name)
-    callback(name, None)
-    return
+    return name, None
 
   r = data['versions'][0]
   if strip_release:
@@ -36,4 +26,4 @@ def _pkg_done(name, strip_release, callback, res):
   else:
     version = r['version']
 
-  callback(name, version)
+  return name, version
diff --git a/nvchecker/source/gcode_hg.py b/nvchecker/source/gcode_hg.py
index d4f3e7e..16800e4 100644
--- a/nvchecker/source/gcode_hg.py
+++ b/nvchecker/source/gcode_hg.py
@@ -4,9 +4,7 @@
 import re
 import time
 import logging
-from functools import partial
-
-from tornado.httpclient import AsyncHTTPClient
+from . import session
 
 logger = logging.getLogger(__name__)
 
@@ -14,14 +12,11 @@ GCODE_URL = 'https://code.google.com/p/%s/source/list'
 GCODE_HG_RE = re.compile(
   r'<a onclick="cancelBubble=true" href="detail\?r=[0-9a-f]+">([^<]+)</a>')
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   repo = conf.get('gcode_hg') or name
   url = GCODE_URL % repo
-  AsyncHTTPClient().fetch(url, user_agent='lilydjwg/nvchecker',
-                          callback=partial(_gcodehg_done, name, callback))
-
-def _gcodehg_done(name, callback, res):
-  data = res.body.decode('utf-8')
+  async with session.get(url) as res:
+    data = await res.text()
   m = GCODE_HG_RE.search(data)
   if m:
     t = time.strptime(m.group(1), '%b %d, %Y')
@@ -29,4 +24,4 @@ def _gcodehg_done(name, callback, res):
   else:
     logger.error('%s: version not found.', name)
     version = None
-  callback(name, version)
+  return name, version
diff --git a/nvchecker/source/gcode_svn.py b/nvchecker/source/gcode_svn.py
index 9c269ed..7b5ece0 100644
--- a/nvchecker/source/gcode_svn.py
+++ b/nvchecker/source/gcode_svn.py
@@ -3,27 +3,22 @@
 
 import re
 import logging
-from functools import partial
-
-from tornado.httpclient import AsyncHTTPClient
+from . import session
 
 logger = logging.getLogger(__name__)
 
 GCODE_URL = 'https://code.google.com/p/%s/source/list'
 GCODE_SVN_RE = re.compile(r'<a href="detail\?r=\d+">r(\d+)</a>')
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   repo = conf.get('gcode_svn') or name
   url = GCODE_URL % repo
-  AsyncHTTPClient().fetch(url, user_agent='lilydjwg/nvchecker',
-                          callback=partial(_gcodehg_done, name, callback))
-
-def _gcodehg_done(name, callback, res):
-  data = res.body.decode('utf-8')
+  async with session.get(url) as res:
+    data = await res.text()
   m = GCODE_SVN_RE.search(data)
   if m:
     version = m.group(1)
   else:
     logger.error('%s: version not found.', name)
     version = None
-  callback(name, version)
+  return name, version
diff --git a/nvchecker/source/github.py b/nvchecker/source/github.py
index 36ac47b..d3a7990 100644
--- a/nvchecker/source/github.py
+++ b/nvchecker/source/github.py
@@ -2,19 +2,15 @@
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
 import os
-import json
-from functools import partial
 
-from tornado.httpclient import AsyncHTTPClient, HTTPRequest
-
-from .base import pycurl
+from . import session
 from ..sortversion import sort_version_keys
 
 GITHUB_URL = 'https://api.github.com/repos/%s/commits?sha=%s'
 GITHUB_LATEST_RELEASE = 'https://api.github.com/repos/%s/releases/latest'
 GITHUB_MAX_TAG = 'https://api.github.com/repos/%s/tags'
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   repo = conf.get('github')
   br = conf.get('branch', 'master')
   use_latest_release = conf.getboolean('use_latest_release', False)
@@ -33,17 +29,9 @@ def get_version(name, conf, callback):
 
   kwargs = {}
   if conf.get('proxy'):
-    if pycurl:
-      kwargs['proxy_host'] = "".join(conf['proxy'].split(':')[:-1])
-      kwargs['proxy_port'] = int(conf['proxy'].split(':')[-1])
-    else:
-      logger.warn('%s: proxy set but not used because pycurl is unavailable.', name)
-  request = HTTPRequest(url, headers=headers, user_agent='lilydjwg/nvchecker', **kwargs)
-  AsyncHTTPClient().fetch(request,
-                          callback=partial(_github_done, name, use_latest_release, use_max_tag, ignored_tags, sort_version_key, callback))
-
-def _github_done(name, use_latest_release, use_max_tag, ignored_tags, sort_version_key, callback, res):
-  data = json.loads(res.body.decode('utf-8'))
+    kwargs["proxy"] = conf.get("proxy")
+  async with session.get(url, headers=headers, **kwargs) as res:
+    data = await res.json()
   if use_latest_release:
     version = data['tag_name']
   elif use_max_tag:
@@ -54,4 +42,4 @@ def _github_done(name, use_latest_release, use_max_tag, ignored_tags, sort_versi
     # YYYYMMDD.HHMMSS
     version = data[0]['commit']['committer']['date'] \
         .rstrip('Z').replace('-', '').replace(':', '').replace('T', '.')
-  callback(name, version)
+  return name, version
diff --git a/nvchecker/source/gitlab.py b/nvchecker/source/gitlab.py
index 97274b5..9298f55 100644
--- a/nvchecker/source/gitlab.py
+++ b/nvchecker/source/gitlab.py
@@ -2,13 +2,10 @@
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
 import os
-import json
-from functools import partial
 import logging
 import urllib.parse
 
-from tornado.httpclient import AsyncHTTPClient, HTTPRequest
-
+from . import session
 from ..sortversion import sort_version_keys
 
 GITLAB_URL = 'https://%s/api/v3/projects/%s/repository/commits?ref_name=%s'
@@ -16,7 +13,7 @@ GITLAB_MAX_TAG = 'https://%s/api/v3/projects/%s/repository/tags'
 
 logger = logging.getLogger(__name__)
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   repo = urllib.parse.quote_plus(conf.get('gitlab'))
   br = conf.get('branch', 'master')
   host = conf.get('host', "gitlab.com")
@@ -28,8 +25,7 @@ def get_version(name, conf, callback):
   token = conf.get('token', os.environ.get(env_name, None))
   if token is None:
     logger.error('%s: No gitlab token specified.', name)
-    callback(name, None)
-    return
+    return name, None
 
   if use_max_tag:
     url = GITLAB_MAX_TAG % (host, repo)
@@ -37,16 +33,12 @@ def get_version(name, conf, callback):
     url = GITLAB_URL % (host, repo, br)
 
   headers = {"PRIVATE-TOKEN": token}
-  request = HTTPRequest(url, headers=headers, user_agent='lilydjwg/nvchecker')
-  AsyncHTTPClient().fetch(request,
-                          callback=partial(_gitlab_done, name, use_max_tag, ignored_tags, sort_version_key, callback))
-
-def _gitlab_done(name, use_max_tag, ignored_tags, sort_version_key, callback, res):
-  data = json.loads(res.body.decode('utf-8'))
+  async with session.get(url, headers=headers) as res:
+    data = await res.json()
   if use_max_tag:
     data = [tag["name"] for tag in data if tag["name"] not in ignored_tags]
     data.sort(key=sort_version_key)
     version = data[-1]
   else:
     version = data[0]['created_at'].split('T', 1)[0].replace('-', '')
-  callback(name, version)
+  return name, version
diff --git a/nvchecker/source/manual.py b/nvchecker/source/manual.py
index ded1c42..5d502cf 100644
--- a/nvchecker/source/manual.py
+++ b/nvchecker/source/manual.py
@@ -1,5 +1,5 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-def get_version(name, conf, callback):
-  callback(name, conf.get('manual'))
+async def get_version(name, conf):
+  return name, conf.get('manual')
diff --git a/nvchecker/source/pacman.py b/nvchecker/source/pacman.py
index 14f1567..9166eae 100644
--- a/nvchecker/source/pacman.py
+++ b/nvchecker/source/pacman.py
@@ -3,15 +3,14 @@
 
 from . import cmd
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   referree = conf.get('pacman') or name
   c = "LANG=C pacman -Si %s | grep -F Version | awk '{print $3}'" % referree
   conf['cmd'] = c
+  strip_release = conf.getboolean('strip-release', False)
 
-  def callback_wrapper(name, version):
-    strip_release = conf.getboolean('strip-release', False)
-    if strip_release and '-' in version:
-      version = version.rsplit('-', 1)[0]
-    callback(name, version)
+  _, version = await cmd.get_version(name, conf)
 
-  cmd.get_version(name, conf, callback_wrapper)
+  if strip_release and '-' in version:
+    version = version.rsplit('-', 1)[0]
+  return name, version
diff --git a/nvchecker/source/regex.py b/nvchecker/source/regex.py
index 282468f..dc709e3 100644
--- a/nvchecker/source/regex.py
+++ b/nvchecker/source/regex.py
@@ -4,50 +4,36 @@
 import re
 import sre_constants
 import logging
-import urllib.parse
-from functools import partial
 
-from tornado.httpclient import AsyncHTTPClient
-
-from .base import pycurl
+from . import session
 from ..sortversion import sort_version_keys
 
 logger = logging.getLogger(__name__)
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   try:
-    r = re.compile(conf['regex'])
+    regex = re.compile(conf['regex'])
   except sre_constants.error:
     logger.warn('%s: bad regex, skipped.', name, exc_info=True)
-    callback(name, None)
-    return
+    return name, None
 
   encoding = conf.get('encoding', 'latin1')
-  httpclient = AsyncHTTPClient()
 
   kwargs = {}
+  headers = {}
   if conf.get('proxy'):
-    if pycurl:
-      host, port = urllib.parse.splitport(conf['proxy'])
-      kwargs['proxy_host'] = host
-      kwargs['proxy_port'] = int(port)
-    else:
-      logger.warn('%s: proxy set but not used because pycurl is unavailable.', name)
+    kwargs["proxy"] = conf.get("proxy")
   if conf.get('user_agent'):
-    kwargs['user_agent'] = conf['user_agent']
+    headers['User-Agent'] = conf['user_agent']
   sort_version_key = sort_version_keys[conf.get("sort_version_key", "parse_version")]
 
-  httpclient.fetch(conf['url'], partial(
-    _got_version, name, r, encoding, sort_version_key, callback
-  ), **kwargs)
-
-def _got_version(name, regex, encoding, sort_version_key, callback, res):
-  version = None
-  try:
-    body = res.body.decode(encoding)
+  async with session.get(conf['url'], headers=headers, **kwargs) as res:
+    version = None
     try:
-      version = max(regex.findall(body), key=sort_version_key)
-    except ValueError:
-      logger.error('%s: version string not found.', name)
-  finally:
-    callback(name, version)
+      body = (await res.read()).decode(encoding)
+      try:
+        version = max(regex.findall(body), key=sort_version_key)
+      except ValueError:
+        logger.error('%s: version string not found.', name)
+    finally:
+      return name, version
diff --git a/nvchecker/source/simple_json.py b/nvchecker/source/simple_json.py
index f4d7539..f70deea 100644
--- a/nvchecker/source/simple_json.py
+++ b/nvchecker/source/simple_json.py
@@ -1,32 +1,20 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-import json
-from functools import partial
-
-from tornado.httpclient import AsyncHTTPClient
-
-from .base import pycurl
+from . import session
 
 def simple_json(urlpat, confkey, version_from_json):
 
-  def get_version(name, conf, callback):
+  async def get_version(name, conf):
     repo = conf.get(confkey) or name
     url = urlpat % repo
     kwargs = {}
     if conf.get('proxy'):
-      if pycurl:
-        kwargs['proxy_host'] = "".join(conf['proxy'].split(':')[:-1])
-        kwargs['proxy_port'] = int(conf['proxy'].split(':')[-1])
-      else:
-        logger.warn('%s: proxy set but not used because pycurl is unavailable.', name)
+      kwargs["proxy"] = conf.get('proxy')
 
-    AsyncHTTPClient().fetch(url, user_agent='lilydjwg/nvchecker',
-                            callback=partial(_json_done, name, callback), **kwargs)
-
-  def _json_done(name, callback, res):
-    data = json.loads(res.body.decode('utf-8'))
+    async with session.get(url, **kwargs) as res:
+      data = await res.json()
     version = version_from_json(data)
-    callback(name, version)
+    return name, version
 
   return get_version
diff --git a/nvchecker/source/vcs.py b/nvchecker/source/vcs.py
index bf9726c..28d663f 100644
--- a/nvchecker/source/vcs.py
+++ b/nvchecker/source/vcs.py
@@ -2,11 +2,7 @@
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
 import logging
-from functools import partial
-
-import tornado.process
-from tornado.ioloop import IOLoop
-
+import asyncio
 from pkg_resources import parse_version
 
 import os.path as _path
@@ -30,7 +26,7 @@ def _parse_oldver(oldver):
         return PROT_VER, 0, ver
     return PROT_VER, count, ver
 
-def get_version(name, conf, callback):
+async def get_version(name, conf):
   vcs = conf['vcs']
   use_max_tag = conf.getboolean('use_max_tag', False)
   ignored_tags = conf.get("ignored_tags", "").split()
@@ -38,33 +34,21 @@ def get_version(name, conf, callback):
   cmd = _cmd_prefix + [name, vcs]
   if use_max_tag:
     cmd += ["get_tags"]
-  p = tornado.process.Subprocess(cmd, io_loop=IOLoop.instance(),
-                                 stdout=tornado.process.Subprocess.STREAM)
-  p.set_exit_callback(partial(_command_done, name, oldver, use_max_tag, ignored_tags, callback, p))
+  p = await asyncio.create_subprocess_exec(*cmd, stdout=asyncio.subprocess.PIPE)
 
-def _command_done(name, oldver, use_max_tag, ignored_tags, callback, process, status):
-  if status != 0:
-    logger.error('%s: command exited with %d.', name, status)
-    callback(name, None)
+  output = (await p.communicate())[0].strip().decode('latin1')
+  if p.returncode != 0:
+    logger.error('%s: command exited with %d.', name, p.returncode)
+    return name, None
   else:
     if use_max_tag:
-      process.stdout.read_until_close(partial(_got_tags_from_cmd,
-                                              callback, name, ignored_tags))
+      data = [tag for tag in output.split("\n") if tag not in ignored_tags]
+      data.sort(key=parse_version)
+      version = data[-1]
+      return name, version
     else:
-      process.stdout.read_until_close(partial(_got_version_from_cmd,
-                                              callback, name, oldver))
-
-def _got_tags_from_cmd(callback, name, ignored_tags, output):
-  output = output.strip().decode('latin1')
-  data = [tag for tag in output.split("\n") if tag not in ignored_tags]
-  data.sort(key=parse_version)
-  version = data[-1]
-  callback(name, version)
-
-def _got_version_from_cmd(callback, name, oldver_str, output):
-  output = output.strip().decode('latin1')
-  oldver = _parse_oldver(oldver_str)
-  if output == oldver[2]:
-      callback(name, None)
-  else:
-      callback(name, "%d.%d.%s" % (oldver[0], oldver[1] + 1, output))
+      oldver = _parse_oldver(oldver)
+      if output == oldver[2]:
+        return name, None
+      else:
+        return name, "%d.%d.%s" % (oldver[0], oldver[1] + 1, output)
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 0000000..08b89b4
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,5 @@
+[flake8]
+ignore = E111, E302, E501
+
+[tool:pytest]
+# addopts = -n auto
diff --git a/setup.py b/setup.py
index 982edcd..3561b1d 100755
--- a/setup.py
+++ b/setup.py
@@ -18,9 +18,11 @@ setup(
   zip_safe = True,
 
   packages = find_packages(exclude=["tests"]),
-  install_requires = ['tornado>=4.1', 'setuptools'],
+  install_requires = ['aiohttp', 'setuptools'],
   tests_require = [
     'pytest',
+    'pytest-asyncio',
+    'pytest-xdist',
     'flaky',
   ],
   entry_points = {
@@ -42,8 +44,8 @@ setup(
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3 :: Only",
-    "Programming Language :: Python :: 3.4",
     "Programming Language :: Python :: 3.5",
+    "Programming Language :: Python :: 3.6",
     "Topic :: Internet",
     "Topic :: Internet :: WWW/HTTP",
     "Topic :: Software Development",
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..988fac3
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,26 @@
+import configparser
+import pytest
+import asyncio
+
+from nvchecker.get_version import get_version as _get_version
+
+@pytest.fixture(scope="module")
+async def get_version():
+    async def __call__(name, config):
+
+        if isinstance(config, dict):
+            _config = configparser.ConfigParser(dict_type=dict, allow_no_value=True)
+            _config.read_dict({name: config})
+            config = _config[name]
+
+        return (await _get_version(name, config))[1]
+
+    return __call__
+
+@pytest.yield_fixture(scope="module")
+def event_loop(request):
+    """Override pytest-asyncio's event_loop fixture,
+       Don't create an instance of the default event loop for each test case.
+    """
+    loop = asyncio.get_event_loop()
+    yield loop
diff --git a/tests/helper.py b/tests/helper.py
deleted file mode 100644
index 2146842..0000000
--- a/tests/helper.py
+++ /dev/null
@@ -1,24 +0,0 @@
-# MIT licensed
-# Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
-
-import configparser
-from tornado.ioloop import IOLoop
-import tornado.testing
-from nvchecker.get_version import get_version
-
-
-class ExternalVersionTestCase(tornado.testing.AsyncTestCase):
-    def get_new_ioloop(self):
-        return IOLoop.instance()
-
-    def sync_get_version(self, name, config):
-        def get_version_callback(name, version):
-            self.stop(version)
-
-        if isinstance(config, dict):
-            _config = configparser.ConfigParser(dict_type=dict, allow_no_value=True)
-            _config.read_dict({name: config})
-            config = _config[name]
-
-        get_version(name, config, get_version_callback)
-        return self.wait()
diff --git a/tests/test_archpkg.py b/tests/test_archpkg.py
index 32d3d48..9e8ffe0 100644
--- a/tests/test_archpkg.py
+++ b/tests/test_archpkg.py
@@ -1,17 +1,14 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-import os
-
+from flaky import flaky
 import pytest
+pytestmark = pytest.mark.asyncio
 
-from tests.helper import ExternalVersionTestCase
+@flaky
+async def test_archpkg(get_version):
+    assert await get_version("ipw2100-fw", {"archpkg": None}) == "1.3-8"
 
-@pytest.mark.skipif("TRAVIS" in os.environ,
-                    reason="Travis-CI has issues connecting to the Arch website")
-class ArchPKGTest(ExternalVersionTestCase):
-    def test_archpkg(self):
-        self.assertEqual(self.sync_get_version("ipw2100-fw", {"archpkg": None}), "1.3-8")
-
-    def test_archpkg_strip_release(self):
-        self.assertEqual(self.sync_get_version("ipw2100-fw", {"archpkg": None, "strip-release": 1}), "1.3")
+@flaky
+async def test_archpkg_strip_release(get_version):
+    assert await get_version("ipw2100-fw", {"archpkg": None, "strip-release": 1}) == "1.3"
diff --git a/tests/test_aur.py b/tests/test_aur.py
index 5a813aa..7c582b7 100644
--- a/tests/test_aur.py
+++ b/tests/test_aur.py
@@ -1,12 +1,14 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+from flaky import flaky
+import pytest
+pytestmark = pytest.mark.asyncio
 
+@flaky
+async def test_aur(get_version):
+    assert await get_version("asciidoc-fake", {"aur": None}) == "1.0-1"
 
-class AURTest(ExternalVersionTestCase):
-    def test_aur(self):
-        self.assertEqual(self.sync_get_version("asciidoc-fake", {"aur": None}), "1.0-1")
-
-    def test_aur_strip_release(self):
-        self.assertEqual(self.sync_get_version("asciidoc-fake", {"aur": None, "strip-release": 1}), "1.0")
+@flaky
+async def test_aur_strip_release(get_version):
+    assert await get_version("asciidoc-fake", {"aur": None, "strip-release": 1}) == "1.0"
diff --git a/tests/test_bitbucket.py b/tests/test_bitbucket.py
index e9df3bd..3f03446 100644
--- a/tests/test_bitbucket.py
+++ b/tests/test_bitbucket.py
@@ -1,14 +1,14 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-class BitBucketTest(ExternalVersionTestCase):
-    def test_bitbucket(self):
-        self.assertEqual(self.sync_get_version("example", {"bitbucket": "prawee/git-tag"}), "20150303")
+async def test_bitbucket(get_version):
+    assert await get_version("example", {"bitbucket": "prawee/git-tag"}) == "20150303"
 
-    def test_bitbucket_max_tag(self):
-        self.assertEqual(self.sync_get_version("example", {"bitbucket": "prawee/git-tag", "use_max_tag": 1}), "1.7.0")
+async def test_bitbucket_max_tag(get_version):
+    assert await get_version("example", {"bitbucket": "prawee/git-tag", "use_max_tag": 1}) == "1.7.0"
 
-    def test_bitbucket_max_tag_with_ignored_tags(self):
-        self.assertEqual(self.sync_get_version("example", {"bitbucket": "prawee/git-tag", "use_max_tag": 1, "ignored_tags": "1.6.0 1.7.0"}), "v1.5")
+async def test_bitbucket_max_tag_with_ignored_tags(get_version):
+    assert await get_version("example", {"bitbucket": "prawee/git-tag", "use_max_tag": 1, "ignored_tags": "1.6.0 1.7.0"}) == "v1.5"
diff --git a/tests/test_cmd.py b/tests/test_cmd.py
index d6cc48d..336f126 100644
--- a/tests/test_cmd.py
+++ b/tests/test_cmd.py
@@ -1,9 +1,11 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
+async def test_cmd(get_version):
+    assert await get_version("example", {"cmd": "echo Meow"}) == "Meow"
 
-class CMDTest(ExternalVersionTestCase):
-    def test_cmd(self):
-        self.assertEqual(self.sync_get_version("example", {"cmd": "echo Meow"}), "Meow")
+async def test_cmd_complex(get_version):
+    assert await get_version("example", {"cmd": "echo Meow | sed 's/meow/woof/i'"}) == "woof"
diff --git a/tests/test_cpan.py b/tests/test_cpan.py
index 3f98f6e..b067e47 100644
--- a/tests/test_cpan.py
+++ b/tests/test_cpan.py
@@ -1,9 +1,8 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-
-class CPANTest(ExternalVersionTestCase):
-    def test_cpan(self):
-        self.assertEqual(self.sync_get_version("POE-Component-Server-HTTPServer", {"cpan": None}), "0.9.2")
+async def test_cpan(get_version):
+    assert await get_version("POE-Component-Server-HTTPServer", {"cpan": None}) == "0.9.2"
diff --git a/tests/test_cratesio.py b/tests/test_cratesio.py
index a046c0d..a5c383b 100644
--- a/tests/test_cratesio.py
+++ b/tests/test_cratesio.py
@@ -1,11 +1,8 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-
-class CratesIOTest(ExternalVersionTestCase):
-    def test_npm(self):
-        self.assertEqual(
-            self.sync_get_version("example", {"cratesio": None}),
-            "0.1.0")
+async def test_cratesio(get_version):
+    assert await get_version("example", {"cratesio": None}) == "0.1.0"
diff --git a/tests/test_debianpkg.py b/tests/test_debianpkg.py
index e4b420a..ead0d63 100644
--- a/tests/test_debianpkg.py
+++ b/tests/test_debianpkg.py
@@ -1,16 +1,14 @@
 # MIT licensed
 # Copyright (c) 2017 Felix Yan <felixonmars@archlinux.org>, et al.
 
-import os
+import pytest
+pytestmark = pytest.mark.asyncio
 
-from tests.helper import ExternalVersionTestCase
+async def test_debianpkg(get_version):
+    assert await get_version("sigrok-firmware-fx2lafw", {"debianpkg": None}) == "0.1.3-1"
 
-class DebianPKGTest(ExternalVersionTestCase):
-    def test_debianpkg(self):
-        self.assertEqual(self.sync_get_version("sigrok-firmware-fx2lafw", {"debianpkg": None}), "0.1.3-1")
+async def test_debianpkg_strip_release(get_version):
+    assert await get_version("sigrok-firmware-fx2lafw", {"debianpkg": None, "strip-release": 1}) == "0.1.3"
 
-    def test_debianpkg_strip_release(self):
-        self.assertEqual(self.sync_get_version("sigrok-firmware-fx2lafw", {"debianpkg": None, "strip-release": 1}), "0.1.3")
-
-    def test_debianpkg_suite(self):
-        self.assertEqual(self.sync_get_version("sigrok-firmware-fx2lafw", {"debianpkg": None, "suite": "jessie"}), "0.1.2-1")
+async def test_debianpkg_suite(get_version):
+    assert await get_version("sigrok-firmware-fx2lafw", {"debianpkg": None, "suite": "jessie"}) == "0.1.2-1"
diff --git a/tests/test_gems.py b/tests/test_gems.py
index ef241a9..844a291 100644
--- a/tests/test_gems.py
+++ b/tests/test_gems.py
@@ -1,9 +1,8 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-
-class RubyGemsTest(ExternalVersionTestCase):
-    def test_gems(self):
-        self.assertEqual(self.sync_get_version("example", {"gems": None}), "1.0.2")
+async def test_gems(get_version):
+    assert await get_version("example", {"gems": None}) == "1.0.2"
diff --git a/tests/test_github.py b/tests/test_github.py
index bc0beef..e5195f2 100644
--- a/tests/test_github.py
+++ b/tests/test_github.py
@@ -3,20 +3,18 @@
 
 import os
 import pytest
-from tests.helper import ExternalVersionTestCase
+pytestmark = [pytest.mark.asyncio,
+              pytest.mark.skipif("NVCHECKER_GITHUB_TOKEN" not in os.environ,
+                                 reason="requires NVCHECKER_GITHUB_TOKEN, or it fails too much")]
 
+async def test_github(get_version):
+    assert await get_version("example", {"github": "harry-sanabria/ReleaseTestRepo"}) == "20140122.012101"
 
-@pytest.mark.skipif("NVCHECKER_GITHUB_TOKEN" not in os.environ,
-                    reason="requires NVCHECKER_GITHUB_TOKEN, or it fails too much")
-class GitHubTest(ExternalVersionTestCase):
-    def test_github(self):
-        self.assertEqual(self.sync_get_version("example", {"github": "harry-sanabria/ReleaseTestRepo"}), "20140122.012101")
+async def test_github_latest_release(get_version):
+    assert await get_version("example", {"github": "harry-sanabria/ReleaseTestRepo", "use_latest_release": 1}) == "release3"
 
-    def test_github_latest_release(self):
-        self.assertEqual(self.sync_get_version("example", {"github": "harry-sanabria/ReleaseTestRepo", "use_latest_release": 1}), "release3")
+async def test_github_max_tag(get_version):
+    assert await get_version("example", {"github": "harry-sanabria/ReleaseTestRepo", "use_max_tag": 1}) == "second_release"
 
-    def test_github_max_tag(self):
-        self.assertEqual(self.sync_get_version("example", {"github": "harry-sanabria/ReleaseTestRepo", "use_max_tag": 1}), "second_release")
-
-    def test_github_max_tag_with_ignored_tags(self):
-        self.assertEqual(self.sync_get_version("example", {"github": "harry-sanabria/ReleaseTestRepo", "use_max_tag": 1, "ignored_tags": "second_release release3"}), "first_release")
+async def test_github_max_tag_with_ignored_tags(get_version):
+    assert await get_version("example", {"github": "harry-sanabria/ReleaseTestRepo", "use_max_tag": 1, "ignored_tags": "second_release release3"}) == "first_release"
diff --git a/tests/test_gitlab.py b/tests/test_gitlab.py
index 8b4d8a8..3e7c381 100644
--- a/tests/test_gitlab.py
+++ b/tests/test_gitlab.py
@@ -3,20 +3,18 @@
 
 import os
 import pytest
-from tests.helper import ExternalVersionTestCase
+pytestmark = [pytest.mark.asyncio,
+              pytest.mark.skipif("NVCHECKER_GITLAB_TOKEN_GITLAB_COM" not in os.environ,
+                                 reason="requires NVCHECKER_GITLAB_TOKEN_GITLAB_COM")]
 
+async def test_gitlab(get_version):
+    ver = await get_version("example",
+                            {"gitlab": "gitlab-org/gitlab-test"})
+    assert len(ver) == 8
+    assert ver.isdigit()
 
-@pytest.mark.skipif("NVCHECKER_GITLAB_TOKEN_GITLAB_COM" not in os.environ,
-                    reason="requires NVCHECKER_GITLAB_TOKEN_GITLAB_COM")
-class GitLabTest(ExternalVersionTestCase):
-    def test_gitlab(self):
-        ver = self.sync_get_version("example",
-                                    {"gitlab": "gitlab-org/gitlab-test"})
-        self.assertEqual(len(ver), 8)
-        self.assertTrue(ver.isdigit())
+async def test_gitlab_max_tag(get_version):
+    assert await get_version("example", {"gitlab": "gitlab-org/gitlab-test", "use_max_tag": 1}) == "v1.1.0"
 
-    def test_gitlab_max_tag(self):
-        self.assertEqual(self.sync_get_version("example", {"gitlab": "gitlab-org/gitlab-test", "use_max_tag": 1}), "v1.1.0")
-
-    def test_gitlab_max_tag_with_ignored_tags(self):
-        self.assertEqual(self.sync_get_version("example", {"gitlab": "gitlab-org/gitlab-test", "use_max_tag": 1, "ignored_tags": "v1.1.0"}), "v1.0.0")
+async def test_gitlab_max_tag_with_ignored_tags(get_version):
+    assert await get_version("example", {"gitlab": "gitlab-org/gitlab-test", "use_max_tag": 1, "ignored_tags": "v1.1.0"}) == "v1.0.0"
diff --git a/tests/test_hackage.py b/tests/test_hackage.py
index d4c5ffc..bc3446d 100644
--- a/tests/test_hackage.py
+++ b/tests/test_hackage.py
@@ -1,9 +1,8 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-
-class HackageTest(ExternalVersionTestCase):
-    def test_hackage(self):
-        self.assertEqual(self.sync_get_version("sessions", {"hackage": None}), "2008.7.18")
+async def test_hackage(get_version):
+    assert await get_version("sessions", {"hackage": None}) == "2008.7.18"
diff --git a/tests/test_manual.py b/tests/test_manual.py
index a81d3ee..7711651 100644
--- a/tests/test_manual.py
+++ b/tests/test_manual.py
@@ -1,9 +1,8 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-
-class ManualTest(ExternalVersionTestCase):
-    def test_manual(self):
-        self.assertEqual(self.sync_get_version("example", {"manual": "Meow"}), "Meow")
+async def test_manual(get_version):
+    assert await get_version("example", {"manual": "Meow"}) == "Meow"
diff --git a/tests/test_npm.py b/tests/test_npm.py
index 5690bce..f3ba06f 100644
--- a/tests/test_npm.py
+++ b/tests/test_npm.py
@@ -1,9 +1,8 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-
-class NPMTest(ExternalVersionTestCase):
-    def test_npm(self):
-        self.assertEqual(self.sync_get_version("example", {"npm": None}), "0.0.0")
+async def test_npm(get_version):
+    assert await get_version("example", {"npm": None}) == "0.0.0"
diff --git a/tests/test_packagist.py b/tests/test_packagist.py
index 47bdd42..7d23086 100644
--- a/tests/test_packagist.py
+++ b/tests/test_packagist.py
@@ -1,9 +1,8 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-
-class PackagistTest(ExternalVersionTestCase):
-    def test_packagist(self):
-        self.assertEqual(self.sync_get_version("butterfly/example-web-application", {"packagist": None}), "1.2.0")
+async def test_packagist(get_version):
+    assert await get_version("butterfly/example-web-application", {"packagist": None}) == "1.2.0"
diff --git a/tests/test_pacman.py b/tests/test_pacman.py
index 81bf351..016889c 100644
--- a/tests/test_pacman.py
+++ b/tests/test_pacman.py
@@ -3,14 +3,12 @@
 
 import shutil
 import pytest
-from tests.helper import ExternalVersionTestCase
+pytestmark = [pytest.mark.asyncio,
+              pytest.mark.skipif(shutil.which("pacman") is None,
+                                 reason="requires pacman command")]
 
+async def test_pacman(get_version):
+    assert await get_version("ipw2100-fw", {"pacman": None}) == "1.3-8"
 
-@pytest.mark.skipif(shutil.which("pacman") is None,
-                    reason="requires pacman command")
-class PacmanTest(ExternalVersionTestCase):
-    def test_pacman(self):
-        self.assertEqual(self.sync_get_version("ipw2100-fw", {"pacman": None}), "1.3-8")
-
-    def test_pacman_strip_release(self):
-        self.assertEqual(self.sync_get_version("ipw2100-fw", {"pacman": None, "strip-release": 1}), "1.3")
+async def test_pacman_strip_release(get_version):
+    assert await get_version("ipw2100-fw", {"pacman": None, "strip-release": 1}) == "1.3"
diff --git a/tests/test_proxy.py b/tests/test_proxy.py
new file mode 100644
index 0000000..0870fbc
--- /dev/null
+++ b/tests/test_proxy.py
@@ -0,0 +1,25 @@
+# MIT licensed
+# Copyright (c) 2017 Felix Yan <felixonmars@archlinux.org>, et al.
+
+import aiohttp
+import pytest
+pytestmark = pytest.mark.asyncio
+
+async def test_proxy(get_version, monkeypatch):
+    from nvchecker.source import session
+
+    async def fake_request(*args, proxy, **kwargs):
+        class fake_response():
+            async def read():
+                return proxy.encode("ascii")
+
+            def release():
+                pass
+
+        return fake_response
+
+    monkeypatch.setattr(session, "nv_config", {"proxy": "255.255.255.255:65535"}, raising=False)
+    monkeypatch.setattr(aiohttp.ClientSession, "_request", fake_request)
+
+    assert await get_version("example", {"regex": "(.+)", "url": "deadbeef"}) == "255.255.255.255:65535"
+    assert await get_version("example", {"regex": "(.+)", "url": "deadbeef", "proxy": "0.0.0.0:0"}) == "0.0.0.0:0"
diff --git a/tests/test_pypi.py b/tests/test_pypi.py
index 9fc4d57..4db6d44 100644
--- a/tests/test_pypi.py
+++ b/tests/test_pypi.py
@@ -1,9 +1,8 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-
-class PyPITest(ExternalVersionTestCase):
-    def test_pypi(self):
-        self.assertEqual(self.sync_get_version("example", {"pypi": None}), "0.1.0")
+async def test_pypi(get_version):
+    assert await get_version("example", {"pypi": None}) == "0.1.0"
diff --git a/tests/test_regex.py b/tests/test_regex.py
index e45bd8f..5f2b084 100644
--- a/tests/test_regex.py
+++ b/tests/test_regex.py
@@ -1,13 +1,12 @@
 # MIT licensed
 # Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from tests.helper import ExternalVersionTestCase
+import pytest
+pytestmark = pytest.mark.asyncio
 
-
-class RegexTest(ExternalVersionTestCase):
-    def test_regex(self):
-        self.assertEqual(self.sync_get_version("example", {
-            "url": "https://httpbin.org/get",
-            "regex": '"User-Agent": "(\w+)"',
-            "user_agent": "Meow",
-        }), "Meow")
+async def test_regex(get_version):
+    assert await get_version("example", {
+        "url": "https://httpbin.org/get",
+        "regex": '"User-Agent": "(\w+)"',
+        "user_agent": "Meow",
+    }) == "Meow"
diff --git a/tests/test_vcs.py b/tests/test_vcs.py
index 26c99bb..4e8061e 100644
--- a/tests/test_vcs.py
+++ b/tests/test_vcs.py
@@ -4,30 +4,29 @@
 import os
 import shutil
 import pytest
-from tests.helper import ExternalVersionTestCase
+pytestmark = pytest.mark.asyncio
 
 
-class VCSTest(ExternalVersionTestCase):
-    @pytest.mark.skipif(shutil.which("git") is None,
-                        reason="requires git command")
-    def test_git(self):
-        os.path.exists("example") or os.mkdir("example")
-        self.assertEqual(self.sync_get_version("example", {"vcs": "git+https://github.com/harry-sanabria/ReleaseTestRepo.git"}), "1.1.2b3cdf6134b07ae6ac77f11b586dc1ae6d1521db")
+@pytest.mark.skipif(shutil.which("git") is None,
+                    reason="requires git command")
+async def test_git(get_version):
+    os.path.exists("example") or os.mkdir("example")
+    assert await get_version("example", {"vcs": "git+https://github.com/harry-sanabria/ReleaseTestRepo.git"}) == "1.1.2b3cdf6134b07ae6ac77f11b586dc1ae6d1521db"
 
-    @pytest.mark.skipif(shutil.which("hg") is None,
-                        reason="requires hg command")
-    def test_mercurial(self):
-        os.path.exists("example") or os.mkdir("example")
-        self.assertEqual(self.sync_get_version("example", {"vcs": "hg+https://bitbucket.org/pil0t/testrepo"}), "1.1.84679e29c7d9")
+@pytest.mark.skipif(shutil.which("hg") is None,
+                    reason="requires hg command")
+async def test_mercurial(get_version):
+    os.path.exists("example") or os.mkdir("example")
+    assert await get_version("example", {"vcs": "hg+https://bitbucket.org/pil0t/testrepo"}) == "1.1.84679e29c7d9"
 
-    @pytest.mark.skipif(shutil.which("git") is None,
-                        reason="requires git command")
-    def test_git_max_tag(self):
-        os.path.exists("example") or os.mkdir("example")
-        self.assertEqual(self.sync_get_version("example", {"vcs": "git+https://github.com/harry-sanabria/ReleaseTestRepo.git", "use_max_tag": 1}), "second_release")
+@pytest.mark.skipif(shutil.which("git") is None,
+                    reason="requires git command")
+async def test_git_max_tag(get_version):
+    os.path.exists("example") or os.mkdir("example")
+    assert await get_version("example", {"vcs": "git+https://github.com/harry-sanabria/ReleaseTestRepo.git", "use_max_tag": 1}) == "second_release"
 
-    @pytest.mark.skipif(shutil.which("git") is None,
-                        reason="requires git command")
-    def test_git_max_tag_with_ignored_tags(self):
-        os.path.exists("example") or os.mkdir("example")
-        self.assertEqual(self.sync_get_version("example", {"vcs": "git+https://github.com/harry-sanabria/ReleaseTestRepo.git", "use_max_tag": 1, "ignored_tags": "second_release release3"}), "first_release")
+@pytest.mark.skipif(shutil.which("git") is None,
+                    reason="requires git command")
+async def test_git_max_tag_with_ignored_tags(get_version):
+    os.path.exists("example") or os.mkdir("example")
+    assert await get_version("example", {"vcs": "git+https://github.com/harry-sanabria/ReleaseTestRepo.git", "use_max_tag": 1, "ignored_tags": "second_release release3"}) == "first_release"