def METHOD_NAME(self):
    """Check tcpdump creates pcap output"""
    self.ping_all_when_learned()
    from_host = self.net.hosts[0]
    to_host = self.net.hosts[1]
    tcpdump_filter = "icmp"
    pcap_file = os.path.join(self.tmpdir, "out.pcap")
    tcpdump_helper = TcpdumpHelper(
        to_host,
        tcpdump_filter,
        [lambda: from_host.cmd("ping -c3 %s" % to_host.IP())],
        pcap_out=pcap_file,
        packets=None,
    )
    tcpdump_helper.execute()
    self._terminate_with_zero(tcpdump_helper)
    result = from_host.cmd("tcpdump -en -r %s" % pcap_file)
    self.assertEqual(result.count("ICMP echo reply"), 3, "three icmp echo replies")