diff --git a/tests/conftest.py b/tests/conftest.py
index caef4250..cb858941 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -200,3 +200,10 @@ def net(request):
     n = _Network()
     request.addfinalizer(n.close)
     return n
+
+def pytest_addoption(parser):
+    parser.addoption('--vmdebug', action='store_true', help='run `test_debug` test')
+
+def pytest_cmdline_preparse(args):
+    if '--vmdebug' in args:
+        args[:] = ['-k', 'test_vmdebug'] + args
diff --git a/tests/regw/Dockerfile b/tests/regw/Dockerfile
index 00c3510f..39b0011c 100644
--- a/tests/regw/Dockerfile
+++ b/tests/regw/Dockerfile
@@ -3,7 +3,7 @@ FROM ubuntu:14.04
 RUN set -o xtrace \
     && sed -i 's,^deb-src,# no src # &,; s,http://archive.ubuntu.com/ubuntu/,mirror://mirrors.ubuntu.com/mirrors.txt,' /etc/apt/sources.list \
     && apt-get update \
-    && apt-get install -y libevent-2.0-5 valgrind
+    && apt-get install -y libevent-2.0-5 valgrind curl
 
 COPY redsocks       /usr/local/sbin/
 COPY redsocks.conf  /usr/local/etc/
diff --git a/tests/run b/tests/run
index 1acb752b..a46c0e38 100755
--- a/tests/run
+++ b/tests/run
@@ -1,3 +1,3 @@
 #!/bin/sh
 
-exec py.test -v
+exec py.test -v "$@"
diff --git a/tests/test_smoke.py b/tests/test_smoke.py
index 43e9887f..bc696948 100644
--- a/tests/test_smoke.py
+++ b/tests/test_smoke.py
@@ -4,12 +4,53 @@
 import conftest
 import pytest
 
-#@pytest.skip # used for debugging
-#def test_sleep(net):
-#    check_call('sleep 1h'.split())
+@pytest.mark.skipif(not pytest.config.getoption('--vmdebug'), reason='need --vmdebug option to run')
+def test_vmdebug(net):
+    check_call('sleep 365d'.split())
 
 @pytest.mark.parametrize('tank', conftest.TANKS.keys())
 def test_smoke(net, tank):
     vm = net.vm['tank%d' % conftest.TANKS[tank]]
     page = vm.do('curl --max-time 0.5 http://10.0.1.80/')
     assert 'Welcome to nginx!' in page
+
+RTT = 200 # ms
+
+@pytest.fixture(scope="function")
+def slow_net(request, net):
+    def close():
+        net.vm['gw'].netcall('tc qdisc del dev ethx root')
+        net.vm['gw'].netcall('tc qdisc del dev ethw root')
+    request.addfinalizer(close)
+    net.vm['gw'].netcall('tc qdisc add dev ethw root netem delay %dms' % (RTT / 2))
+    net.vm['gw'].netcall('tc qdisc add dev ethx root netem delay %dms' % (RTT / 2))
+    return net
+
+LATENCY = {
+    'connect_none':     3 * RTT,
+    'connect_basic':    3 * RTT,
+    'connect_digest':   3 * RTT,
+    'socks5_none':      4 * RTT,
+    'socks5_auth':      5 * RTT,
+    'regw_direct':      2 * RTT,
+}
+
+def http_ping(vm):
+    vm.do('curl -o /dev/null http://10.0.1.80/') # heatup L2 and auth caches
+    s = vm.do('curl -sS -w %{{time_connect}}/%{{time_total}}/%{{http_code}}/%{{size_download}} -o /dev/null http://10.0.1.80/')
+    connect, total, code, size = s.split('/')
+    connect, total, code, size = float(connect) * 1000, float(total) * 1000, int(code), int(size)
+    return connect, total, code, size
+
+@pytest.mark.parametrize('tank', conftest.TANKS.keys())
+def test_latency_tank(slow_net, tank):
+    vm = slow_net.vm['tank%d' % conftest.TANKS[tank]]
+    connect, total, code, size = http_ping(vm)
+    assert code == 200 and size == 612
+    assert connect < 0.005 and LATENCY[tank]-RTT*.2 < total and total < LATENCY[tank]+RTT*.2
+
+def test_latency_regw(slow_net):
+    vm, tank = slow_net.vm['regw'], 'regw_direct'
+    connect, total, code, size = http_ping(vm)
+    assert code == 200 and size == 612
+    assert RTT*.8 < connect and connect < RTT*1.2 and LATENCY[tank]-RTT*.2 < total and total < LATENCY[tank]+RTT*.2