Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Newsgroups: comp.lang.python
Subject: Re: Python Unit test
Date: Wed, 27 Jan 2016 07:54:25 -0500
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On Tue, 26 Jan 2016 20:57:19 -0800 (PST), toluagboola@gmail.com declaimed
the following:

>import getopt, sys
>import dpkt, pcap
>
>def usage():
>    print >>sys.stderr, 'usage: %s [-i device] [pattern]' % sys.argv[0]
>    sys.exit(1)
>
>def main():
>    opts, args = getopt.getopt(sys.argv[1:], 'i:h')
>    name = None
>    for o, a in opts:
>        if o == '-i': name = a
>        else: usage()
>        
>    pc = pcap.pcap(name)
>    pc.setfilter(' '.join(args))
>    decode = { pcap.DLT_LOOP:dpkt.loopback.Loopback,
>               pcap.DLT_NULL:dpkt.loopback.Loopback,
>               pcap.DLT_EN10MB:dpkt.ethernet.Ethernet }[pc.datalink()]
>    try:
>        print 'listening on %s: %s' % (pc.name, pc.filter)
>        for ts, pkt in pc:
>            print ts, `decode(pkt)`
>    except KeyboardInterrupt:
>        nrecv, ndrop, nifdrop = pc.stats()
>        print '\n%d packets received by filter' % nrecv
>        print '%d packets dropped by kernel' % ndrop
>
>if __name__ == '__main__':
>    main()
>
>
>Here is what the python code looks like and I am to make a Unittest for it

	Off-hand -- you will find a "unit" test to be rather difficult for that
example; there aren't any "units" that can be readily tested.

	The unittest module relies upon creating methods that invoke operations
in the program with known inputs, and that then compare the known/expected
results to what the operation has produced.

	At the least, from what I can tell, that means you have to mock up some
way to feed a known stream of packets to the Ethernet connection, possible
with a known timestamp, which satisfies the filter... and maybe some
packets that don't so you can confirm they don't get through.

	You don't have anything "callable" that returns results. If the end of
main() looked more like:

	except KeyboardInterrupt:	#don't know how to do that in a test
		return pc.stats()

THEN you might be able to create a unittest where the unit being tested is
main itself

	def test_main(...):
		nr, nd, ni = main()	#somehow it needs to end
		assertEqual(nr, 20, "received packet count not 20")

which relies upon somehow having a known feed to the packet sniffer, and
some way to end the main function.

-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/