cleaned up and commented test_simpleperf.py

examples/test/test_simpleperf.py

@@ -1,10 +1,12 @@
 #!/usr/bin/env python
 
-"""TEST"""
+"""
+Test for simpleperf.py
+"""
 
 import unittest
 import pexpect
-from time import sleep
+import re
 from mininet.log import setLogLevel
 from mininet.net import Mininet
 from mininet.node import CPULimitedHost
@@ -13,24 +15,36 @@ from mininet.link import TCLink
 from mininet.examples.simpleperf import SingleSwitchTopo
 
 class testSimplePerf( unittest.TestCase ):
-    "Test ping with single switch topology (common code)."
-
 
     def testE2E( self ):
-        results = [ "Results:", pexpect.EOF, pexpect.TIMEOUT ]
+        "Run the example and verify ping and iperf results"
         p = pexpect.spawn( 'python -m mininet.examples.simpleperf' )
-        index = p.expect( results, timeout=600 )
-        self.assertEqual( index, 0 )
+        # check ping results
+        p.expect( "Results: (\d+)% dropped", timeout=120 )
+        loss = int( p.match.group( 1 ) )
+        self.assertTrue( loss > 0 and loss < 100 )
+        # check iperf results
+        p.expect( "Results: \['([\d\.]+) .bits/sec", timeout=480 )
+        bw = float( p.match.group( 1 ) )
+        self.assertTrue( bw > 0 )
         p.wait()
 
     def testTopo( self ):
-        topo = SingleSwitchTopo(n=4)
-        net = Mininet(topo=topo,
-                  host=CPULimitedHost, link=TCLink)
+        """Import SingleSwitchTopo from example and test connectivity between two hosts
+           Note: this test may fail very rarely because it is non-deterministic
+           i.e. links are configured with 10% packet loss, but if we get unlucky and 
+           none or all of the packets are dropped, the test will fail"""
+        topo = SingleSwitchTopo( n=4 )
+        net = Mininet( topo=topo, host=CPULimitedHost, link=TCLink )
         net.start()
-        h1, h4 = net.get('h1', 'h4')
-        h1.cmd( 'ping -c 1 %s' % h4.IP() )
+        h1, h4 = net.get( 'h1', 'h4' )
+        # have h1 ping h4 ten times
+        expectStr = '(\d+) packets transmitted, (\d+) received, (\d+)% packet loss'
+        output = h1.cmd( 'ping -c 10 %s' % h4.IP() )
+        m = re.search( expectStr, output )
+        loss = int( m.group( 3 ) )
         net.stop()
+        self.assertTrue( loss > 0 and loss < 100 )
 
 if __name__ == '__main__':
     setLogLevel( 'warning' )