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6
The Importance of Testing
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=========================
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Reliability is a critical success factor for any Version Control System.
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Reliability is a critical success factor for any version control system.
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We want Bazaar to be highly reliable across multiple platforms while
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evolving over time to meet the needs of its community.
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.. _testrepository: https://launchpad.net/testrepository
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Babune continuous integration
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-----------------------------
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We have a Hudson continuous-integration system that automatically runs
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tests across various platforms. In the future we plan to add more
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combinations including testing plugins. See
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<http://babune.ladeuil.net:24842/>. (Babune = Bazaar Buildbot Network.)
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Running tests in parallel
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-------------------------
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Bazaar can use subunit to spawn multiple test processes. There is
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slightly more chance you will hit ordering or timing-dependent bugs but
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$ ./bzr selftest --parallel=fork
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Note that you will need the Subunit library
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<https://launchpad.net/subunit/> to use this, which is in
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``python-subunit`` on Ubuntu.
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Running tests from a ramdisk
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----------------------------
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The tests create and delete a lot of temporary files. In some cases you
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can make the test suite run much faster by running it on a ramdisk. For
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$ sudo mount -t tmpfs none /ram
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$ TMPDIR=/ram ./bzr selftest ...
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You could also change ``/tmp`` in ``/etc/fstab`` to have type ``tmpfs``,
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if you don't mind possibly losing other files in there when the machine
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restarts. Add this line (if there is none for ``/tmp`` already)::
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none /tmp tmpfs defaults 0 0
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With a 6-core machine and ``--parallel=fork`` using a tmpfs doubles the
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test execution speed.
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The actual use of ScriptRunner within a TestCase looks something like
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def test_unshelve_keep(self):
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sr.run_script(self, '''
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$ bzr shelve --all -m Foo
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$ bzr unshelve --keep
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from bzrlib.tests import script
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def test_unshelve_keep(self):
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script.run_script(self, '''
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$ bzr shelve --all -m Foo
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$ bzr unshelve --keep
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You can also test commands that read user interaction::
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def test_confirm_action(self):
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"""You can write tests that demonstrate user confirmation"""
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commands.builtin_command_registry.register(cmd_test_confirm)
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self.addCleanup(commands.builtin_command_registry.remove, 'test-confirm')
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2>Really do it? [y/n]:
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Import tariff tests
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-------------------
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dependencies and only needed for particular cases. If they're loaded in
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other cases then bzr may break for people who don't have those modules.
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`test_import_tarrif` allows us to check that removal of imports doesn't
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`test_import_tariff` allows us to check that removal of imports doesn't
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This is done by running the command in a subprocess with
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_test_needs_features = [features.apport]
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Testing deprecated code
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-----------------------
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When code is deprecated, it is still supported for some length of time,
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usually until the next major version. The ``applyDeprecated`` helper
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wraps calls to deprecated code to verify that it is correctly issuing the
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deprecation warning, and also prevents the warnings from being printed
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Typically patches that apply the ``@deprecated_function`` decorator should
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update the accompanying tests to use the ``applyDeprecated`` wrapper.
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``applyDeprecated`` is defined in ``bzrlib.tests.TestCase``. See the API
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docs for more details.
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Testing exceptions and errors
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-----------------------------
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A base TestCase that extends the Python standard library's
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TestCase in several ways. It adds more assertion methods (e.g.
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``assertContainsRe``), ``addCleanup``, and other features (see its API
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docs for details). It also has a ``setUp`` that makes sure that
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global state like registered hooks and loggers won't interfere with
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your test. All tests should use this base class (whether directly or
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TestCase in several ways. TestCase is build on
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``testtools.TestCase``, which gives it support for more assertion
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methods (e.g. ``assertContainsRe``), ``addCleanup``, and other
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features (see its API docs for details). It also has a ``setUp`` that
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makes sure that global state like registered hooks and loggers won't
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interfere with your test. All tests should use this base class
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(whether directly or via a subclass). Note that we are trying not to
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add more assertions at this point, and instead to build up a library
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of ``bzrlib.tests.matchers``.
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TestCaseWithMemoryTransport
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Extends TestCase and adds methods like ``get_transport``,
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Please see bzrlib.treebuilder for more details.
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Temporarily changing state
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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If your test needs to temporarily mutate some global state, and you need
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it restored at the end, you can say for example::
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self.overrideAttr(osutils, '_cached_user_encoding', 'latin-1')
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Our base ``TestCase`` class provides an ``addCleanup`` method, which
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should be used instead of ``tearDown``. All the cleanups are run when the
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test finishes, regardless of whether it passes or fails. If one cleanup
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fails, later cleanups are still run.
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(The same facility is available outside of tests through
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Generally we prefer automated testing but sometimes a manual test is the
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right thing, especially for performance tests that want to measure elapsed
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time rather than effort.
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Simulating slow networks
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------------------------
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To get realistically slow network performance for manually measuring
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performance, we can simulate 500ms latency (thus 1000ms round trips)::
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$ sudo tc qdisc add dev lo root netem delay 500ms
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Normal system behaviour is restored with ::
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$ sudo tc qdisc del dev lo root
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A more precise version that only filters traffic to port 4155 is::
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tc qdisc add dev lo root handle 1: prio
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tc qdisc add dev lo parent 1:3 handle 30: netem delay 500ms
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tc qdisc add dev lo parent 30:1 handle 40: prio
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tc filter add dev lo protocol ip parent 1:0 prio 3 u32 match ip dport 4155 0xffff flowid 1:3 handle 800::800
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tc filter add dev lo protocol ip parent 1:0 prio 3 u32 match ip sport 4155 0xffff flowid 1:3 handle 800::801
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tc filter del dev lo protocol ip parent 1: pref 3 u32
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tc qdisc del dev lo root handle 1:
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You can use similar code to add additional delay to a real network
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interface, perhaps only when talking to a particular server or pointing at
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a VM. For more information see <http://lartc.org/>.
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.. |--| unicode:: U+2014
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doc/developers/testing.txt
