1 .. _unittest: https://docs.python.org/2/library/unittest.html
2 .. _TestCase: https://docs.python.org/2/library/unittest.html#unittest.TestCase
3 .. _AssertionError: https://docs.python.org/2/library/exceptions.html#exceptions.AssertionError
4 .. _SkipTest: https://docs.python.org/2/library/unittest.html#unittest.SkipTest
5 .. _virtualenv: http://docs.python-guide.org/en/latest/dev/virtualenvs/
6 .. _scapy: http://www.secdev.org/projects/scapy/
7 .. _logging: https://docs.python.org/2/library/logging.html
9 .. |vtf| replace:: VPP Test Framework
21 The goal of the |vtf| is to ease writing, running and debugging
22 unit tests for the VPP. For this, python was chosen as a high level language
23 allowing rapid development with scapy_ providing the necessary tool for creating
24 and dissecting packets.
26 Anatomy of a test case
27 ######################
29 Python's unittest_ is used as the base framework upon which the VPP test
30 framework is built. A test suite in the |vtf| consists of multiple classes
31 derived from `VppTestCase`, which is itself derived from TestCase_.
32 The test class defines one or more test functions, which act as test cases.
34 Function flow when running a test case is:
36 1. `setUpClass <VppTestCase.setUpClass>`:
37 This function is called once for each test class, allowing a one-time test
38 setup to be executed. If this functions throws an exception,
39 none of the test functions are executed.
40 2. `setUp <VppTestCase.setUp>`:
41 The setUp function runs before each of the test functions. If this function
42 throws an exception other than AssertionError_ or SkipTest_, then this is
43 considered an error, not a test failure.
45 This is the guts of the test case. It should execute the test scenario
46 and use the various assert functions from the unittest framework to check
47 necessary. Multiple test_<name> methods can exist in a test case.
48 4. `tearDown <VppTestCase.tearDown>`:
49 The tearDown function is called after each test function with the purpose
50 of doing partial cleanup.
51 5. `tearDownClass <VppTestCase.tearDownClass>`:
52 Method called once after running all of the test functions to perform
58 Each test case has a logger automatically created for it, stored in
59 'logger' property, based on logging_. Use the logger's standard methods
60 debug(), info(), error(), ... to emit log messages to the logger.
62 All the log messages go always into a log file in temporary directory
65 To control the messages printed to console, specify the V= parameter.
69 make test # minimum verbosity
70 make test V=1 # moderate verbosity
71 make test V=2 # maximum verbosity
73 Test temporary directory and VPP life cycle
74 ###########################################
76 Test separation is achieved by separating the test files and vpp instances.
77 Each test creates a temporary directory and it's name is used to create
78 a shared memory prefix which is used to run a VPP instance.
79 The temporary directory name contains the testcase class name for easy
80 reference, so for testcase named 'TestVxlan' the directory could be named
81 e.g. vpp-unittest-TestVxlan-UNUP3j.
82 This way, there is no conflict between any other VPP instances running
83 on the box and the test VPP. Any temporary files created by the test case
84 are stored in this temporary test directory.
86 The test temporary directory holds the following interesting files:
88 * log.txt - this contains the logger output on max verbosity
89 * pg*_in.pcap - last injected packet stream into VPP, named after the interface,
90 so for pg0, the file will be named pg0_in.pcap
91 * pg*_out.pcap - last capture file created by VPP for interface, similarly,
92 named after the interface, so for e.g. pg1, the file will be named
94 * history files - whenever the capture is restarted or a new stream is added,
95 the existing files are rotated and renamed, soo all the pcap files
96 are always saved for later debugging if needed
97 * core - if vpp dumps a core, it'll be stored in the temporary directory
98 * vpp_stdout.txt - file containing output which vpp printed to stdout
99 * vpp_stderr.txt - file containing output which vpp printed to stderr
101 *NOTE*: existing temporary directories named vpp-unittest-* are automatically
102 removed when invoking 'make test*' or 'make retest*' to keep the temporary
108 Virtualenv_ is a python module which provides a means to create an environment
109 containing the dependencies required by the |vtf|, allowing a separation
110 from any existing system-wide packages. |vtf|'s Makefile automatically
111 creates a virtualenv_ inside build-root and installs the required packages
112 in that environment. The environment is entered whenever executing a test
113 via one of the make test targets.
118 Most unit tests do some kind of packet manipulation - sending and receiving
119 packets between VPP and virtual hosts connected to the VPP. Referring
120 to the sides, addresses, etc. is always done as if looking from the VPP side,
123 * *local_* prefix is used for the VPP side.
124 So e.g. `local_ip4 <VppInterface.local_ip4>` address is the IPv4 address
125 assigned to the VPP interface.
126 * *remote_* prefix is used for the virtual host side.
127 So e.g. `remote_mac <VppInterface.remote_mac>` address is the MAC address
128 assigned to the virtual host connected to the VPP.
130 Automatically generated addresses
131 #################################
133 To send packets, one needs to typically provide some addresses, otherwise
134 the packets will be dropped. The interface objects in |vtf| automatically
135 provide addresses based on (typically) their indexes, which ensures
136 there are no conflicts and eases debugging by making the addressing scheme
139 The developer of a test case typically doesn't need to work with the actual
140 numbers, rather using the properties of the objects. The addresses typically
141 come in two flavors: '<address>' and '<address>n' - note the 'n' suffix.
142 The former address is a Python string, while the latter is translated using
143 socket.inet_pton to raw format in network byte order - this format is suitable
144 for passing as an argument to VPP APIs.
146 e.g. for the IPv4 address assigned to the VPP interface:
148 * local_ip4 - Local IPv4 address on VPP interface (string)
149 * local_ip4n - Local IPv4 address - raw, suitable as API parameter.
151 These addresses need to be configured in VPP to be usable using e.g.
152 `config_ip4` API. Please see the documentation to `VppInterface` for more
155 By default, there is one remote address of each kind created for L3:
156 remote_ip4 and remote_ip6. If the test needs more addresses, because it's
157 simulating more remote hosts, they can be generated using
158 `generate_remote_hosts` API and the entries for them inserted into the ARP
159 table using `configure_ipv4_neighbors` API.
161 Packet flow in the |vtf|
162 ########################
164 Test framework -> VPP
165 ~~~~~~~~~~~~~~~~~~~~~
167 |vtf| doesn't send any packets to VPP directly. Traffic is instead injected
168 using packet-generator interfaces, represented by the `VppPGInterface` class.
169 Packets are written into a temporary .pcap file, which is then read by the VPP
170 and the packets are injected into the VPP world.
172 To add a list of packets to an interface, call the `add_stream` method on that
173 interface. Once everything is prepared, call `pg_start` method to start
174 the packet generator on the VPP side.
176 VPP -> test framework
177 ~~~~~~~~~~~~~~~~~~~~~
179 Similarly, VPP doesn't send any packets to |vtf| directly. Instead, packet
180 capture feature is used to capture and write traffic to a temporary .pcap file,
181 which is then read and analyzed by the |vtf|.
183 The following APIs are available to the test case for reading pcap files.
185 * `get_capture`: this API is suitable for bulk & batch style of test, where
186 a list of packets is prepared & sent, then the received packets are read
187 and verified. The API needs the number of packets which are expected to
188 be captured (ignoring filtered packets - see below) to know when the pcap
189 file is completely written by the VPP. If using packet infos for verifying
190 packets, then the counts of the packet infos can be automatically used
191 by `get_capture` to get the proper count (in this case the default value
192 None can be supplied as expected_count or ommitted altogether).
193 * `wait_for_packet`: this API is suitable for interactive style of test,
194 e.g. when doing session management, three-way handsakes, etc. This API waits
195 for and returns a single packet, keeping the capture file in place
196 and remembering context. Repeated invocations return following packets
197 (or raise Exception if timeout is reached) from the same capture file
198 (= packets arriving on the same interface).
200 *NOTE*: it is not recommended to mix these APIs unless you understand how they
201 work internally. None of these APIs rotate the pcap capture file, so calling
202 e.g. `get_capture` after `wait_for_packet` will return already read packets.
203 It is safe to switch from one API to another after calling `enable_capture`
204 as that API rotates the capture file.
206 Automatic filtering of packets:
207 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
209 Both APIs (`get_capture` and `wait_for_packet`) by default filter the packet
210 capture, removing known uninteresting packets from it - these are IPv6 Router
211 Advertisments and IPv6 Router Alerts. These packets are unsolicitated
212 and from the point of |vtf| are random. If a test wants to receive these
213 packets, it should specify either None or a custom filtering function
214 as the value to the 'filter_out_fn' argument.
216 Common API flow for sending/receiving packets:
217 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
219 We will describe a simple scenario, where packets are sent from pg0 to pg1
220 interface, assuming that the interfaces were created using
221 `create_pg_interfaces` API.
223 1. Create a list of packets for pg0::
226 packets = create_packets(src=self.pg0, dst=self.pg1,
229 2. Add that list of packets to the source interface::
231 self.pg0.add_stream(packets)
233 3. Enable capture on the destination interface::
235 self.pg1.enable_capture()
237 4. Start the packet generator::
241 5. Wait for capture file to appear and read it::
243 capture = self.pg1.get_capture(expected_count=packet_count)
245 6. Verify packets match sent packets::
247 self.verify_capture(send=packets, captured=capture)
249 Test framework objects
250 ######################
252 The following objects provide VPP abstraction and provide a means to do
253 common tasks easily in the test cases.
255 * `VppInterface`: abstract class representing generic VPP interface
256 and contains some common functionality, which is then used by derived classes
257 * `VppPGInterface`: class representing VPP packet-generator interface.
258 The interface is created/destroyed when the object is created/destroyed.
259 * `VppSubInterface`: VPP sub-interface abstract class, containing common
260 functionality for e.g. `VppDot1QSubint` and `VppDot1ADSubint` classes
262 How VPP APIs/CLIs are called
263 ############################
265 Vpp provides python bindings in a python module called vpp-papi, which the test
266 framework installs in the virtual environment. A shim layer represented by
267 the `VppPapiProvider` class is built on top of the vpp-papi, serving these
270 1. Automatic return value checks:
271 After each API is called, the return value is checked against the expected
272 return value (by default 0, but can be overridden) and an exception
273 is raised if the check fails.
274 2. Automatic call of hooks:
276 a. `before_cli <Hook.before_cli>` and `before_api <Hook.before_api>` hooks
277 are used for debug logging and stepping through the test
278 b. `after_cli <Hook.after_cli>` and `after_api <Hook.after_api>` hooks
279 are used for monitoring the vpp process for crashes
280 3. Simplification of API calls:
281 Many of the VPP APIs take a lot of parameters and by providing sane defaults
282 for these, the API is much easier to use in the common case and the code is
283 more readable. E.g. ip_add_del_route API takes ~25 parameters, of which
284 in the common case, only 3 are needed.
289 Some interesting utility methods are:
291 * `ppp`: 'Pretty Print Packet' - returns a string containing the same output
292 as Scapy's packet.show() would print
293 * `ppc`: 'Pretty Print Capture' - returns a string containing printout of
294 a capture (with configurable limit on the number of packets printed from it)
297 *NOTE*: Do not use Scapy's packet.show() in the tests, because it prints
298 the output to stdout. All output should go to the logger associated with
301 Example: how to add a new test
302 ##############################
304 In this example, we will describe how to add a new test case which tests
305 basic IPv4 forwarding.
307 1. Add a new file called test_ip4_fwd.py in the test directory, starting
310 from framework import VppTestCase
311 from scapy.layers.l2 import Ether
312 from scapy.packet import Raw
313 from scapy.layers.inet import IP, UDP
314 from random import randint
316 2. Create a class inherited from the VppTestCase::
318 class IP4FwdTestCase(VppTestCase):
319 """ IPv4 simple forwarding test case """
321 2. Add a setUpClass function containing the setup needed for our test to run::
324 def setUpClass(self):
325 super(IP4FwdTestCase, self).setUpClass()
326 self.create_pg_interfaces(range(2)) # create pg0 and pg1
327 for i in self.pg_interfaces:
328 i.admin_up() # put the interface up
329 i.config_ip4() # configure IPv4 address on the interface
330 i.resolve_arp() # resolve ARP, so that we know VPP MAC
332 3. Create a helper method to create the packets to send::
334 def create_stream(self, src_if, dst_if, count):
336 for i in range(count):
337 # create packet info stored in the test case instance
338 info = self.create_packet_info(src_if, dst_if)
339 # convert the info into packet payload
340 payload = self.info_to_payload(info)
341 # create the packet itself
342 p = (Ether(dst=src_if.local_mac, src=src_if.remote_mac) /
343 IP(src=src_if.remote_ip4, dst=dst_if.remote_ip4) /
344 UDP(sport=randint(1000, 2000), dport=5678) /
346 # store a copy of the packet in the packet info
348 # append the packet to the list
351 # return the created packet list
354 4. Create a helper method to verify the capture::
356 def verify_capture(self, src_if, dst_if, capture):
358 for packet in capture:
362 # convert the payload to packet info object
363 payload_info = self.payload_to_info(str(packet[Raw]))
364 # make sure the indexes match
365 self.assert_equal(payload_info.src, src_if.sw_if_index,
366 "source sw_if_index")
367 self.assert_equal(payload_info.dst, dst_if.sw_if_index,
368 "destination sw_if_index")
369 packet_info = self.get_next_packet_info_for_interface2(
373 # make sure we didn't run out of saved packets
374 self.assertIsNotNone(packet_info)
375 self.assert_equal(payload_info.index, packet_info.index,
377 saved_packet = packet_info.data # fetch the saved packet
378 # assert the values match
379 self.assert_equal(ip.src, saved_packet[IP].src,
381 # ... more assertions here
382 self.assert_equal(udp.sport, saved_packet[UDP].sport,
385 self.logger.error(ppp("Unexpected or invalid packet:",
388 remaining_packet = self.get_next_packet_info_for_interface2(
392 self.assertIsNone(remaining_packet,
393 "Interface %s: Packet expected from interface "
394 "%s didn't arrive" % (dst_if.name, src_if.name))
396 5. Add the test code to test_basic function::
398 def test_basic(self):
400 # create the packet stream
401 packets = self.create_stream(self.pg0, self.pg1, count)
402 # add the stream to the source interface
403 self.pg0.add_stream(packets)
404 # enable capture on both interfaces
405 self.pg0.enable_capture()
406 self.pg1.enable_capture()
407 # start the packet generator
409 # get capture - the proper count of packets was saved by
410 # create_packet_info() based on dst_if parameter
411 capture = self.pg1.get_capture()
412 # assert nothing captured on pg0 (always do this last, so that
413 # some time has already passed since pg_start())
414 self.pg0.assert_nothing_captured()
416 self.verify_capture(self.pg0, self.pg1, capture)
418 6. Run the test by issuing 'make test'.