Wireshark Tests

The recommended steps to prepare for and to run tests:

* Install two Python packages, pytest: `pip install pytest pytest-xdist`
* Build programs (“wireshark”, “tshark”, etc.): `ninja`
* Build additional programs for the “unittests” suite: `ninja test-programs`
* Run tests in the build directory: `pytest`

Replace `ninja test-programs` by `make test-programs` as needed.

See the “Wireshark Tests” chapter of the Developer's Guide for details:
https://www.wireshark.org/docs/wsdg_html_chunked/ChapterTests.html

If you need to update the baseline files use the following commands (on a Linux or macOS system)
TZ=UTC WIRESHARK_RUN_FROM_BUILD_DIRECTORY=1 build/run/tshark --global-profile -T ek -r test/captures/dhcp.pcap > test/baseline/dhcp.ek
TZ=UTC WIRESHARK_RUN_FROM_BUILD_DIRECTORY=1 build/run/tshark --global-profile -T json -r test/captures/dhcp.pcap > test/baseline/dhcp.json
TZ=UTC WIRESHARK_RUN_FROM_BUILD_DIRECTORY=1 build/run/tshark --global-profile -T json -o protocols.display_abs_time_ascii:ALWAYS -r test/captures/dhcp.pcap > test/baseline/dhcp-asctime.json
TZ=UTC WIRESHARK_RUN_FROM_BUILD_DIRECTORY=1 build/run/tshark --global-profile -T jsonraw -r test/captures/dhcp.pcap > test/baseline/dhcp.jsonraw
TZ=UTC WIRESHARK_RUN_FROM_BUILD_DIRECTORY=1 build/run/tshark --global-profile -T ek -r test/captures/dhcp.pcap -x > test/baseline/dhcp-raw.ek