It is possible to test OVN using both tooling provided with Open vSwitch and using a variety of third party tooling.

Built-in Tooling

OVN provides a number of different test suites and other tooling for validating basic functionality of OVN. Before running any of the tests described here, you must bootstrap, configure and build OVN as described in OVN on Linux, FreeBSD and NetBSD. You do not need to install OVN, Open vSwitch or to build or load the kernel module to run these test suites.You do not need supervisor privilege to run these test suites.

Unit Tests

OVN includes a suite of self-tests. Before you submit patches upstream, we advise that you run the tests and ensure that they pass. If you add new features to OVN, then adding tests for those features will ensure your features don’t break as developers modify other areas of OVN.

To run all the unit tests in OVN, one at a time, run:

$ make check

This takes under 5 minutes on a modern desktop system.

To run all the unit tests in OVN in parallel, run:

$ make check TESTSUITEFLAGS=-j8

You can run up to eight threads. This takes under a minute on a modern 4-core desktop system.

To see a list of all the available tests, run:

$ make check TESTSUITEFLAGS=--list

To run only a subset of tests, e.g. test 123 and tests 477 through 484, run:

$ make check TESTSUITEFLAGS='123 477-484'

Tests do not have inter-dependencies, so you may run any subset.

To run tests matching a keyword, e.g. ovsdb, run:

$ make check TESTSUITEFLAGS='-k ovsdb'

To see a complete list of test options, run:

$ make check TESTSUITEFLAGS=--help

The results of a testing run are reported in tests/testsuite.log. Report report test failures as bugs and include the testsuite.log in your report.


Sometimes a few tests may fail on some runs but not others. This is usually a bug in the testsuite, not a bug in OVN itself. If you find that a test fails intermittently, please report it, since the developers may not have noticed. You can make the testsuite automatically rerun tests that fail, by adding RECHECK=yes to the make command line, e.g.:

$ make check TESTSUITEFLAGS=-j8 RECHECK=yes

Debugging unit tests

To initiate debugging from artifacts generated from make check run, set the OVS_PAUSE_TEST environment variable to 1. For example, to run test case 139 and pause on error:

$ OVS_PAUSE_TEST=1 make check TESTSUITEFLAGS='-v 139'

When error occurs, above command would display something like this:

Set environment variable to use various ovs utilities
export OVS_RUNDIR=<dir>/ovs/_build-gcc/tests/testsuite.dir/0139
Press ENTER to continue:

And from another window, one can execute ovs-xxx commands like:

export OVS_RUNDIR=/opt/vdasari/Developer/ovs/_build-gcc/tests/testsuite.dir/0139
$ ovs-ofctl dump-ports br0

Once done with investigation, press ENTER to perform cleanup operation.

OVS_PAUSE_TEST=1 only pauses failed tests when run with ‘-v’ option. Tests run without ‘-v’, or successful tests, are not paused.


If the build was configured with --enable-coverage and the lcov utility is installed, you can run the testsuite and generate a code coverage report by using the check-lcov target:

$ make check-lcov

All the same options are available via TESTSUITEFLAGS. For example:

$ make check-lcov TESTSUITEFLAGS='-j8 -k ovn'


If you have valgrind installed, you can run the testsuite under valgrind by using the check-valgrind target:

$ make check-valgrind

When you do this, the “valgrind” results for test <N> are reported in files named tests/testsuite.dir/<N>/valgrind.*.

To test the testsuite of kernel datapath under valgrind, you can use the check-kernel-valgrind target and find the “valgrind” results under directory tests/system-kmod-testsuite.dir/.

All the same options are available via TESTSUITEFLAGS.


You may find that the valgrind results are easier to interpret if you put -q in ~/.valgrindrc, since that reduces the amount of output.

Static Code Analysis

Static Analysis is a method of debugging Software by examining code rather than actually executing it. This can be done through ‘scan-build’ commandline utility which internally uses clang (or) gcc to compile the code and also invokes a static analyzer to do the code analysis. At the end of the build, the reports are aggregated in to a common folder and can later be analyzed using ‘scan-view’.

OVN includes a Makefile target to trigger static code analysis:

$ ./boot.sh
$ ./configure CC=clang  # clang
# or
$ ./configure CC=gcc CFLAGS="-std=gnu99"  # gcc
$ make clang-analyze

You should invoke scan-view to view analysis results. The last line of output from clang-analyze will list the command (containing results directory) that you should invoke to view the results on a browser.

Datapath testing

OVN includes a suite of tests specifically for datapath functionality. The datapath tests make some assumptions about the environment. They must be run under root privileges on a Linux system with support for network namespaces. Make sure no other Open vSwitch instance is running the test suite. These tests may take several minutes to complete, and cannot be run in parallel.

To invoke the datapath testsuite with the OVS userspace datapath, run:

$ make check-system-userspace

The results of the userspace testsuite appear in tests/system-userspace-testsuite.dir.

To invoke the datapath testsuite with the OVS kernel datapath, run:

$ make check-kernel

The results of the kernel testsuite appear in tests/system-kmod-testsuite.dir.

The tests themselves must run as root. If you do not run make as root, then you can specify a program to get superuser privileges as SUDO=<program>, e.g. the following uses sudo (the -E option is needed to pass through environment variables):

$ make check-system-userspace SUDO='sudo -E'

The testsuite creates and destroys tap devices named ovs-netdev and br0. If it is interrupted during a test, then before it can be restarted, you may need to destroy these devices with commands like the following:

$ ip tuntap del dev ovs-netdev mode tap
$ ip tuntap del dev br0 mode tap

All the features documented under Unit Tests are available for the datapath testsuites, except that the datapath testsuites do not support running tests in parallel.

Performance testing

OVN includes a suite of micro-benchmarks to aid a developer in understanding the performance impact of any changes that they are making. They can be used to help to understand the relative performance between two test runs on the same test machine, but are not intended to give the absolute performance of OVN.

To invoke the performance testsuite, run:

$ make check-perf

This will run all available performance tests. Some of these tests may be long-running as they need to build complex logical network topologies. In order to speed up subsequent test runs, some objects (e.g. the Northbound DB) may be cached. In order to force the tests to rebuild all these objects, run:

$ make check-perf TESTSUITEFLAGS="--rebuild"

A typical workflow for a developer trying to improve the performance of OVN would be the following:

  1. Optional: Modify/add a performance test to buld the topology that you are benchmarking, if required.

  2. Run make check-perf TESTSUITEFLAGS="--rebuild" to generate cached databases (and complete a test run). The results of each test run are displayed on the screen at the end of the test run but are also saved in the file tests/perf-testsuite.dir/results.


This step may take some time depending on the number of tests that are being rebuilt, the complexity of the tests and the performance of the test machine. If you are only using one test, you can specify the test to run by adding the test number to the make command. (e.g. make check-perf TESTSUITEFLAGS="--rebuild <test number>")

  1. Run make check-perf to measure the performance metric that you are benchmarking against. If you are only using one test, you can specify the test to run by adding the test number to the make command. (e.g. make check-perf TESTSUITEFLAGS="--rebuild <test number>")

  2. Modify OVN code to implement the change that you believe will improve the performance.

  3. Go to Step 2. to continue making improvements.

If, as a developer, you modify a performance test in a way that may change one of these cached objects, be sure to rebuild the test.

The cached objects are stored under the relevant folder in tests/perf-testsuite.dir/cached.