waitConnected and debug output for testMultiPing

This test fails periodically on Travis (#714)

Hopefully waiting for connection will make it more reliable,
and if not then the debug output will help.

examples/multiping.py

@@ -45,7 +45,7 @@ def multiping( netsize, chunksize, seconds):
 
     # Create network and identify subnets
     topo = SingleSwitchTopo( netsize )
-    net = Mininet( topo=topo )
+    net = Mininet( topo=topo, waitConnected=True )
     net.start()
     hosts = net.hosts
     subnets = chunks( hosts, chunksize )

examples/test/test_multiping.py

@@ -31,18 +31,20 @@ class testMultiPing( unittest.TestCase ):
                 target = p.match.group(3)
                 received = int( p.match.group(4) )
                 if target == '10.0.0.200':
-                    self.assertEqual( received, 0 )
+                    self.assertEqual( received, 0, p.match.group(0) + '\n' +
+                                      target + ' received %d != 0 packets' % received )
                 else:
-                    self.assertEqual( received, 1 )
+                    self.assertEqual( received, 1, p.match.group(0) + '\n' +
+                                      target + ' received %d != 1 packets' % received )
                 try:
                     pings[ name ].remove( target )
                 except:
                     pass
             else:
                 break
-        self.assertTrue( len( pings ) > 0 )
+        self.assertTrue( len( pings ) > 0, 'too few pings' )
         for t in pings.values():
-            self.assertEqual( len( t ), 0 )
+            self.assertEqual( len( t ), 0, 'missed ping target(s): %s' % t )
 
 if __name__ == '__main__':
     unittest.main()