new_contents: #!/usr/bin/env python
  
  """Package: mininet
     Test functions defined in mininet.util."""
  
  import unittest
  
  from mininet.util import quietRun
  
  class testQuietRun( unittest.TestCase ):
      """Test quietRun that runs a command and returns its merged output from
      STDOUT and STDIN"""
  
      @staticmethod
      def getEchoCmd( n ):
          "Return a command that will print n characters"
          return "echo -n " + "x" * n
  
      def testEmpty( self ):
          "Run a command that prints nothing"
          output = quietRun(testQuietRun.getEchoCmd( 0 ) )
          self.assertEqual( 0, len( output ) )
  
      def testOneRead( self ):
          """Run a command whose output is entirely read on the first call if
          each call reads at most 1024 characters
          """
          for n in [ 42, 1024 ]:
              output = quietRun( testQuietRun.getEchoCmd( n ) )
              self.assertEqual( n, len( output ) )
  
      def testMultipleReads( self ):
          "Run a command whose output is not entirely read on the first read"
          for n in [ 1025, 4242 ]:
              output = quietRun(testQuietRun.getEchoCmd( n ) )
              self.assertEqual( n, len( output ) )
  
  if __name__ == "__main__":
      unittest.main()
  
subject: Add unit tests for util