Add more information for test condition failure

examples/test/test_linearbandwidth.py

@@ -34,8 +34,11 @@ def testLinearBandwidth( self ):
                     bw *= 10 ** 9
                 # check that we have a previous result to compare to
                 if n != 1:
-                    self.assertTrue( bw < previous_bw )
-                previous_bw = bw
+                    info = ( 'bw: %d bits/s across %d switches, '
+                             'previous: %d bits/s across %d switches' %
+                             ( bw, n, previous_bw, previous_n ) )
+                    self.assertTrue( bw < previous_bw, info )
+                previous_bw, previous_n = bw, n
             else:
                 break