CI problem seems to be caused by not started Ryu controller.
diff --git a/src/emuvim/test/base.py b/src/emuvim/test/base.py
index f652259..13ace1b 100644
--- a/src/emuvim/test/base.py
+++ b/src/emuvim/test/base.py
@@ -8,6 +8,7 @@
 import docker
 from emuvim.dcemulator.net import DCNetwork
 from mininet.clean import cleanup
+from mininet.node import Controller
 
 class SimpleTestTopology(unittest.TestCase):
     """
@@ -32,7 +33,7 @@
         Creates a Mininet instance and automatically adds some
         nodes to it.
         """
-        self.net = net = DCNetwork()
+        self.net = DCNetwork()
 
         # add some switches
         for i in range(0, nswitches):
diff --git a/src/emuvim/test/test_emulator.py b/src/emuvim/test/test_emulator.py
index d552f1f..fb8714a 100755
--- a/src/emuvim/test/test_emulator.py
+++ b/src/emuvim/test/test_emulator.py
@@ -40,7 +40,7 @@
         # stop Mininet network
         self.stopNet()
 
-    @unittest.skip("disabled to test if CI fails because this is the first test.")
+    #@unittest.skip("disabled to test if CI fails because this is the first test.")
     def testMultipleDatacenterDirect(self):
         """
         Create a two data centers and interconnect them.
@@ -57,7 +57,6 @@
         assert(len(self.getDockernetContainers()) == 0)
         assert(len(self.net.hosts) == 2)
         assert(len(self.net.switches) == 2)
-        time.sleep(5)
         # check connectivity by using ping
         assert(self.net.ping([self.h[0], self.h[1]]) <= 0.0)
         # stop Mininet network