6
The Importance of Testing
7
=========================
9
Reliability is a critical success factor for any version control system.
10
We want Bazaar to be highly reliable across multiple platforms while
11
evolving over time to meet the needs of its community.
13
In a nutshell, this is what we expect and encourage:
15
* New functionality should have test cases. Preferably write the
16
test before writing the code.
18
In general, you can test at either the command-line level or the
19
internal API level. See `Writing tests`_ below for more detail.
21
* Try to practice Test-Driven Development: before fixing a bug, write a
22
test case so that it does not regress. Similarly for adding a new
23
feature: write a test case for a small version of the new feature before
24
starting on the code itself. Check the test fails on the old code, then
25
add the feature or fix and check it passes.
27
By doing these things, the Bazaar team gets increased confidence that
28
changes do what they claim to do, whether provided by the core team or
29
by community members. Equally importantly, we can be surer that changes
30
down the track do not break new features or bug fixes that you are
33
As of September 2009, Bazaar ships with a test suite containing over
34
23,000 tests and growing. We are proud of it and want to remain so. As
35
community members, we all benefit from it. Would you trust version control
36
on your project to a product *without* a test suite like Bazaar has?
39
Running the Test Suite
40
======================
42
As of Bazaar 2.1, you must have the testtools_ library installed to run
45
.. _testtools: https://launchpad.net/testtools/
47
To test all of Bazaar, just run::
51
With ``--verbose`` bzr will print the name of every test as it is run.
53
This should always pass, whether run from a source tree or an installed
54
copy of Bazaar. Please investigate and/or report any failures.
57
Running particular tests
58
------------------------
60
Currently, bzr selftest is used to invoke tests.
61
You can provide a pattern argument to run a subset. For example,
62
to run just the blackbox tests, run::
64
./bzr selftest -v blackbox
66
To skip a particular test (or set of tests), use the --exclude option
67
(shorthand -x) like so::
69
./bzr selftest -v -x blackbox
71
To ensure that all tests are being run and succeeding, you can use the
72
--strict option which will fail if there are any missing features or known
75
./bzr selftest --strict
77
To list tests without running them, use the --list-only option like so::
79
./bzr selftest --list-only
81
This option can be combined with other selftest options (like -x) and
82
filter patterns to understand their effect.
84
Once you understand how to create a list of tests, you can use the --load-list
85
option to run only a restricted set of tests that you kept in a file, one test
86
id by line. Keep in mind that this will never be sufficient to validate your
87
modifications, you still need to run the full test suite for that, but using it
88
can help in some cases (like running only the failed tests for some time)::
90
./bzr selftest -- load-list my_failing_tests
92
This option can also be combined with other selftest options, including
93
patterns. It has some drawbacks though, the list can become out of date pretty
94
quick when doing Test Driven Development.
96
To address this concern, there is another way to run a restricted set of tests:
97
the --starting-with option will run only the tests whose name starts with the
98
specified string. It will also avoid loading the other tests and as a
99
consequence starts running your tests quicker::
101
./bzr selftest --starting-with bzrlib.blackbox
103
This option can be combined with all the other selftest options including
104
--load-list. The later is rarely used but allows to run a subset of a list of
105
failing tests for example.
110
To test only the bzr core, ignoring any plugins you may have installed,
113
./bzr --no-plugins selftest
115
Disabling crash reporting
116
-------------------------
118
By default Bazaar uses apport_ to report program crashes. In developing
119
Bazaar it's normal and expected to have it crash from time to time, at
120
least because a test failed if for no other reason.
122
Therefore you should probably add ``debug_flags = no_apport`` to your
123
``bazaar.conf`` file (in ``~/.bazaar/`` on Unix), so that failures just
124
print a traceback rather than writing a crash file.
126
.. _apport: https://launchpad.net/apport/
129
Test suite debug flags
130
----------------------
132
Similar to the global ``-Dfoo`` debug options, bzr selftest accepts
133
``-E=foo`` debug flags. These flags are:
135
:allow_debug: do *not* clear the global debug flags when running a test.
136
This can provide useful logging to help debug test failures when used
137
with e.g. ``bzr -Dhpss selftest -E=allow_debug``
139
Note that this will probably cause some tests to fail, because they
140
don't expect to run with any debug flags on.
146
Bazaar can optionally produce output in the machine-readable subunit_
147
format, so that test output can be post-processed by various tools. To
148
generate a subunit test stream::
150
$ ./bzr selftest --subunit
152
Processing such a stream can be done using a variety of tools including:
154
* The builtin ``subunit2pyunit``, ``subunit-filter``, ``subunit-ls``,
155
``subunit2junitxml`` from the subunit project.
157
* tribunal_, a GUI for showing test results.
159
* testrepository_, a tool for gathering and managing test runs.
161
.. _subunit: https://launchpad.net/subunit/
162
.. _tribunal: https://launchpad.net/tribunal/
168
Bazaar ships with a config file for testrepository_. This can be very
169
useful for keeping track of failing tests and doing general workflow
170
support. To run tests using testrepository::
174
To run only failing tests::
176
$ testr run --failing
178
To run only some tests, without plugins::
180
$ test run test_selftest -- --no-plugins
182
See the testrepository documentation for more details.
184
.. _testrepository: https://launchpad.net/testrepository
187
Babune continuous integration
188
-----------------------------
190
We have a Hudson continuous-integration system that automatically runs
191
tests across various platforms. In the future we plan to add more
192
combinations including testing plugins. See
193
<http://babune.ladeuil.net:24842/>. (Babune = Bazaar Buildbot Network.)
196
Running tests in parallel
197
-------------------------
199
Bazaar can use subunit to spawn multiple test processes. There is
200
slightly more chance you will hit ordering or timing-dependent bugs but
203
$ ./bzr selftest --parallel=fork
205
Note that you will need the Subunit library
206
<https://launchpad.net/subunit/> to use this, which is in
207
``python-subunit`` on Ubuntu.
210
Running tests from a ramdisk
211
----------------------------
213
The tests create and delete a lot of temporary files. In some cases you
214
can make the test suite run much faster by running it on a ramdisk. For
218
$ sudo mount -t tmpfs none /ram
219
$ TMPDIR=/ram ./bzr selftest ...
221
You could also change ``/tmp`` in ``/etc/fstab`` to have type ``tmpfs``,
222
if you don't mind possibly losing other files in there when the machine
223
restarts. Add this line (if there is none for ``/tmp`` already)::
225
none /tmp tmpfs defaults 0 0
227
With a 6-core machine and ``--parallel=fork`` using a tmpfs doubles the
228
test execution speed.
234
Normally you should add or update a test for all bug fixes or new features
238
Where should I put a new test?
239
------------------------------
241
Bzrlib's tests are organised by the type of test. Most of the tests in
242
bzr's test suite belong to one of these categories:
245
- Blackbox (UI) tests
246
- Per-implementation tests
249
A quick description of these test types and where they belong in bzrlib's
250
source follows. Not all tests fall neatly into one of these categories;
251
in those cases use your judgement.
257
Unit tests make up the bulk of our test suite. These are tests that are
258
focused on exercising a single, specific unit of the code as directly
259
as possible. Each unit test is generally fairly short and runs very
262
They are found in ``bzrlib/tests/test_*.py``. So in general tests should
263
be placed in a file named test_FOO.py where FOO is the logical thing under
266
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
267
See bzrlib/tests/test_sampler.py for a template test script.
273
Tests can be written for the UI or for individual areas of the library.
274
Choose whichever is appropriate: if adding a new command, or a new command
275
option, then you should be writing a UI test. If you are both adding UI
276
functionality and library functionality, you will want to write tests for
277
both the UI and the core behaviours. We call UI tests 'blackbox' tests
278
and they belong in ``bzrlib/tests/blackbox/*.py``.
280
When writing blackbox tests please honour the following conventions:
282
1. Place the tests for the command 'name' in
283
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
284
to locate the test script for a faulty command.
286
2. Use the 'self.run_bzr("name")' utility function to invoke the command
287
rather than running bzr in a subprocess or invoking the
288
cmd_object.run() method directly. This is a lot faster than
289
subprocesses and generates the same logging output as running it in a
290
subprocess (which invoking the method directly does not).
292
3. Only test the one command in a single test script. Use the bzrlib
293
library when setting up tests and when evaluating the side-effects of
294
the command. We do this so that the library api has continual pressure
295
on it to be as functional as the command line in a simple manner, and
296
to isolate knock-on effects throughout the blackbox test suite when a
297
command changes its name or signature. Ideally only the tests for a
298
given command are affected when a given command is changed.
300
4. If you have a test which does actually require running bzr in a
301
subprocess you can use ``run_bzr_subprocess``. By default the spawned
302
process will not load plugins unless ``--allow-plugins`` is supplied.
305
Per-implementation tests
306
~~~~~~~~~~~~~~~~~~~~~~~~
308
Per-implementation tests are tests that are defined once and then run
309
against multiple implementations of an interface. For example,
310
``per_transport.py`` defines tests that all Transport implementations
311
(local filesystem, HTTP, and so on) must pass. They are found in
312
``bzrlib/tests/per_*/*.py``, and ``bzrlib/tests/per_*.py``.
314
These are really a sub-category of unit tests, but an important one.
316
Along the same lines are tests for extension modules. We generally have
317
both a pure-python and a compiled implementation for each module. As such,
318
we want to run the same tests against both implementations. These can
319
generally be found in ``bzrlib/tests/*__*.py`` since extension modules are
320
usually prefixed with an underscore. Since there are only two
321
implementations, we have a helper function
322
``bzrlib.tests.permute_for_extension``, which can simplify the
323
``load_tests`` implementation.
329
We make selective use of doctests__. In general they should provide
330
*examples* within the API documentation which can incidentally be tested. We
331
don't try to test every important case using doctests |--| regular Python
332
tests are generally a better solution. That is, we just use doctests to make
333
our documentation testable, rather than as a way to make tests. Be aware that
334
doctests are not as well isolated as the unit tests, if you need more
335
isolation, you're likely want to write unit tests anyway if only to get a
336
better control of the test environment.
338
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
340
__ http://docs.python.org/lib/module-doctest.html
342
There is an `assertDoctestExampleMatches` method in
343
`bzrlib.tests.TestCase` that allows you to match against doctest-style
344
string templates (including ``...`` to skip sections) from regular Python
351
``bzrlib/tests/script.py`` allows users to write tests in a syntax very
352
close to a shell session, using a restricted and limited set of commands
353
that should be enough to mimic most of the behaviours.
355
A script is a set of commands, each command is composed of:
357
* one mandatory command line,
358
* one optional set of input lines to feed the command,
359
* one optional set of output expected lines,
360
* one optional set of error expected lines.
362
Input, output and error lines can be specified in any order.
364
Except for the expected output, all lines start with a special
365
string (based on their origin when used under a Unix shell):
367
* '$ ' for the command,
369
* nothing for output,
372
Comments can be added anywhere, they start with '#' and end with
375
The execution stops as soon as an expected output or an expected error is not
378
If output occurs and no output is expected, the execution stops and the
379
test fails. If unexpected output occurs on the standard error, then
380
execution stops and the test fails.
382
If an error occurs and no expected error is specified, the execution stops.
384
An error is defined by a returned status different from zero, not by the
385
presence of text on the error stream.
387
The matching is done on a full string comparison basis unless '...' is used, in
388
which case expected output/errors can be less precise.
392
The following will succeeds only if 'bzr add' outputs 'adding file'::
397
If you want the command to succeed for any output, just use::
403
or use the ``--quiet`` option::
407
The following will stop with an error::
411
If you want it to succeed, use::
414
2> bzr: ERROR: unknown command "not-a-command"
416
You can use ellipsis (...) to replace any piece of text you don't want to be
419
$ bzr branch not-a-branch
420
2>bzr: ERROR: Not a branch...not-a-branch/".
422
This can be used to ignore entire lines too::
428
# And here we explain that surprising fourth line
435
You can check the content of a file with cat::
440
You can also check the existence of a file with cat, the following will fail if
441
the file doesn't exist::
445
You can run files containing shell-like scripts with::
447
$ bzr test-script <script>
449
where ``<script>`` is the path to the file containing the shell-like script.
451
The actual use of ScriptRunner within a TestCase looks something like
454
from bzrlib.tests import script
456
def test_unshelve_keep(self):
458
script.run_script(self, '''
460
$ bzr shelve -q --all -m Foo
463
$ bzr unshelve -q --keep
470
You can also test commands that read user interaction::
472
def test_confirm_action(self):
473
"""You can write tests that demonstrate user confirmation"""
474
commands.builtin_command_registry.register(cmd_test_confirm)
475
self.addCleanup(commands.builtin_command_registry.remove, 'test-confirm')
478
2>Really do it? [y/n]:
483
To avoid having to specify "-q" for all commands whose output is
484
irrelevant, the run_script() method may be passed the keyword argument
485
``null_output_matches_anything=True``. For example::
487
def test_ignoring_null_output(self):
490
$ bzr ci -m 'first revision' --unchanged
493
""", null_output_matches_anything=True)
499
`bzrlib.tests.test_import_tariff` has some tests that measure how many
500
Python modules are loaded to run some representative commands.
502
We want to avoid loading code unnecessarily, for reasons including:
504
* Python modules are interpreted when they're loaded, either to define
505
classes or modules or perhaps to initialize some structures.
507
* With a cold cache we may incur blocking real disk IO for each module.
509
* Some modules depend on many others.
511
* Some optional modules such as `testtools` are meant to be soft
512
dependencies and only needed for particular cases. If they're loaded in
513
other cases then bzr may break for people who don't have those modules.
515
`test_import_tariff` allows us to check that removal of imports doesn't
518
This is done by running the command in a subprocess with
519
``PYTHON_VERBOSE=1``. Starting a whole Python interpreter is pretty slow,
520
so we don't want exhaustive testing here, but just enough to guard against
521
distinct fixed problems.
523
Assertions about precisely what is loaded tend to be brittle so we instead
524
make assertions that particular things aren't loaded.
526
Unless selftest is run with ``--no-plugins``, modules will be loaded in
527
the usual way and checks made on what they cause to be loaded. This is
528
probably worth checking into, because many bzr users have at least some
529
plugins installed (and they're included in binary installers).
531
In theory, plugins might have a good reason to load almost anything:
532
someone might write a plugin that opens a network connection or pops up a
533
gui window every time you run 'bzr status'. However, it's more likely
534
that the code to do these things is just being loaded accidentally. We
535
might eventually need to have a way to make exceptions for particular
538
Some things to check:
540
* non-GUI commands shouldn't load GUI libraries
542
* operations on bzr native formats sholudn't load foreign branch libraries
544
* network code shouldn't be loaded for purely local operations
546
* particularly expensive Python built-in modules shouldn't be loaded
547
unless there is a good reason
550
Testing locking behaviour
551
-------------------------
553
In order to test the locking behaviour of commands, it is possible to install
554
a hook that is called when a write lock is: acquired, released or broken.
555
(Read locks also exist, they cannot be discovered in this way.)
557
A hook can be installed by calling bzrlib.lock.Lock.hooks.install_named_hook.
558
The three valid hooks are: `lock_acquired`, `lock_released` and `lock_broken`.
565
lock.Lock.hooks.install_named_hook('lock_acquired',
566
locks_acquired.append, None)
567
lock.Lock.hooks.install_named_hook('lock_released',
568
locks_released.append, None)
570
`locks_acquired` will now receive a LockResult instance for all locks acquired
571
since the time the hook is installed.
573
The last part of the `lock_url` allows you to identify the type of object that is locked.
575
- BzrDir: `/branch-lock`
576
- Working tree: `/checkout/lock`
577
- Branch: `/branch/lock`
578
- Repository: `/repository/lock`
580
To test if a lock is a write lock on a working tree, one can do the following::
582
self.assertEndsWith(locks_acquired[0].lock_url, "/checkout/lock")
584
See bzrlib/tests/commands/test_revert.py for an example of how to use this for
591
In our enhancements to unittest we allow for some addition results beyond
592
just success or failure.
594
If a test can't be run, it can say that it's skipped by raising a special
595
exception. This is typically used in parameterized tests |--| for example
596
if a transport doesn't support setting permissions, we'll skip the tests
597
that relating to that. ::
600
return self.branch_format.initialize(repo.bzrdir)
601
except errors.UninitializableFormat:
602
raise tests.TestSkipped('Uninitializable branch format')
604
Raising TestSkipped is a good idea when you want to make it clear that the
605
test was not run, rather than just returning which makes it look as if it
608
Several different cases are distinguished:
611
Generic skip; the only type that was present up to bzr 0.18.
614
The test doesn't apply to the parameters with which it was run.
615
This is typically used when the test is being applied to all
616
implementations of an interface, but some aspects of the interface
617
are optional and not present in particular concrete
618
implementations. (Some tests that should raise this currently
619
either silently return or raise TestSkipped.) Another option is
620
to use more precise parameterization to avoid generating the test
624
The test can't be run because a dependency (typically a Python
625
library) is not available in the test environment. These
626
are in general things that the person running the test could fix
627
by installing the library. It's OK if some of these occur when
628
an end user runs the tests or if we're specifically testing in a
629
limited environment, but a full test should never see them.
631
See `Test feature dependencies`_ below.
634
The test exists but is known to fail, for example this might be
635
appropriate to raise if you've committed a test for a bug but not
636
the fix for it, or if something works on Unix but not on Windows.
638
Raising this allows you to distinguish these failures from the
639
ones that are not expected to fail. If the test would fail
640
because of something we don't expect or intend to fix,
641
KnownFailure is not appropriate, and TestNotApplicable might be
644
KnownFailure should be used with care as we don't want a
645
proliferation of quietly broken tests.
649
We plan to support three modes for running the test suite to control the
650
interpretation of these results. Strict mode is for use in situations
651
like merges to the mainline and releases where we want to make sure that
652
everything that can be tested has been tested. Lax mode is for use by
653
developers who want to temporarily tolerate some known failures. The
654
default behaviour is obtained by ``bzr selftest`` with no options, and
655
also (if possible) by running under another unittest harness.
657
======================= ======= ======= ========
658
result strict default lax
659
======================= ======= ======= ========
660
TestSkipped pass pass pass
661
TestNotApplicable pass pass pass
662
UnavailableFeature fail pass pass
663
KnownFailure fail pass pass
664
======================= ======= ======= ========
667
Test feature dependencies
668
-------------------------
670
Writing tests that require a feature
671
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
673
Rather than manually checking the environment in each test, a test class
674
can declare its dependence on some test features. The feature objects are
675
checked only once for each run of the whole test suite.
677
(For historical reasons, as of May 2007 many cases that should depend on
678
features currently raise TestSkipped.)
682
class TestStrace(TestCaseWithTransport):
684
_test_needs_features = [StraceFeature]
686
This means all tests in this class need the feature. If the feature is
687
not available the test will be skipped using UnavailableFeature.
689
Individual tests can also require a feature using the ``requireFeature``
692
self.requireFeature(StraceFeature)
694
The old naming style for features is CamelCase, but because they're
695
actually instances not classses they're now given instance-style names
698
Features already defined in ``bzrlib.tests`` and ``bzrlib.tests.features``
706
- UnicodeFilenameFeature
708
- CaseInsensitiveFilesystemFeature.
709
- chown_feature: The test can rely on OS being POSIX and python
711
- posix_permissions_feature: The test can use POSIX-style
712
user/group/other permission bits.
715
Defining a new feature that tests can require
716
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
718
New features for use with ``_test_needs_features`` or ``requireFeature``
719
are defined by subclassing ``bzrlib.tests.Feature`` and overriding the
720
``_probe`` and ``feature_name`` methods. For example::
722
class _SymlinkFeature(Feature):
725
return osutils.has_symlinks()
727
def feature_name(self):
730
SymlinkFeature = _SymlinkFeature()
732
A helper for handling running tests based on whether a python
733
module is available. This can handle 3rd-party dependencies (is
734
``paramiko`` available?) as well as stdlib (``termios``) or
735
extension modules (``bzrlib._groupcompress_pyx``). You create a
736
new feature instance with::
738
# in bzrlib/tests/features.py
739
apport = tests.ModuleAvailableFeature('apport')
742
# then in bzrlib/tests/test_apport.py
743
class TestApportReporting(TestCaseInTempDir):
745
_test_needs_features = [features.apport]
748
Testing deprecated code
749
-----------------------
751
When code is deprecated, it is still supported for some length of time,
752
usually until the next major version. The ``applyDeprecated`` helper
753
wraps calls to deprecated code to verify that it is correctly issuing the
754
deprecation warning, and also prevents the warnings from being printed
757
Typically patches that apply the ``@deprecated_function`` decorator should
758
update the accompanying tests to use the ``applyDeprecated`` wrapper.
760
``applyDeprecated`` is defined in ``bzrlib.tests.TestCase``. See the API
761
docs for more details.
764
Testing exceptions and errors
765
-----------------------------
767
It's important to test handling of errors and exceptions. Because this
768
code is often not hit in ad-hoc testing it can often have hidden bugs --
769
it's particularly common to get NameError because the exception code
770
references a variable that has since been renamed.
772
.. TODO: Something about how to provoke errors in the right way?
774
In general we want to test errors at two levels:
776
1. A test in ``test_errors.py`` checking that when the exception object is
777
constructed with known parameters it produces an expected string form.
778
This guards against mistakes in writing the format string, or in the
779
``str`` representations of its parameters. There should be one for
780
each exception class.
782
2. Tests that when an api is called in a particular situation, it raises
783
an error of the expected class. You should typically use
784
``assertRaises``, which in the Bazaar test suite returns the exception
785
object to allow you to examine its parameters.
787
In some cases blackbox tests will also want to check error reporting. But
788
it can be difficult to provoke every error through the commandline
789
interface, so those tests are only done as needed |--| eg in response to a
790
particular bug or if the error is reported in an unusual way(?) Blackbox
791
tests should mostly be testing how the command-line interface works, so
792
should only test errors if there is something particular to the cli in how
793
they're displayed or handled.
799
The Python ``warnings`` module is used to indicate a non-fatal code
800
problem. Code that's expected to raise a warning can be tested through
803
The test suite can be run with ``-Werror`` to check no unexpected errors
806
However, warnings should be used with discretion. It's not an appropriate
807
way to give messages to the user, because the warning is normally shown
808
only once per source line that causes the problem. You should also think
809
about whether the warning is serious enought that it should be visible to
810
users who may not be able to fix it.
813
Interface implementation testing and test scenarios
814
---------------------------------------------------
816
There are several cases in Bazaar of multiple implementations of a common
817
conceptual interface. ("Conceptual" because it's not necessary for all
818
the implementations to share a base class, though they often do.)
819
Examples include transports and the working tree, branch and repository
822
In these cases we want to make sure that every implementation correctly
823
fulfils the interface requirements. For example, every Transport should
824
support the ``has()`` and ``get()`` and ``clone()`` methods. We have a
825
sub-suite of tests in ``test_transport_implementations``. (Most
826
per-implementation tests are in submodules of ``bzrlib.tests``, but not
827
the transport tests at the moment.)
829
These tests are repeated for each registered Transport, by generating a
830
new TestCase instance for the cross product of test methods and transport
831
implementations. As each test runs, it has ``transport_class`` and
832
``transport_server`` set to the class it should test. Most tests don't
833
access these directly, but rather use ``self.get_transport`` which returns
834
a transport of the appropriate type.
836
The goal is to run per-implementation only the tests that relate to that
837
particular interface. Sometimes we discover a bug elsewhere that happens
838
with only one particular transport. Once it's isolated, we can consider
839
whether a test should be added for that particular implementation,
840
or for all implementations of the interface.
842
See also `Per-implementation tests`_ (above).
845
Test scenarios and variations
846
-----------------------------
848
Some utilities are provided for generating variations of tests. This can
849
be used for per-implementation tests, or other cases where the same test
850
code needs to run several times on different scenarios.
852
The general approach is to define a class that provides test methods,
853
which depend on attributes of the test object being pre-set with the
854
values to which the test should be applied. The test suite should then
855
also provide a list of scenarios in which to run the tests.
857
A single *scenario* is defined by a `(name, parameter_dict)` tuple. The
858
short string name is combined with the name of the test method to form the
859
test instance name. The parameter dict is merged into the instance's
864
load_tests = load_tests_apply_scenarios
866
class TestCheckout(TestCase):
868
scenarios = multiply_scenarios(
869
VaryByRepositoryFormat(),
873
The `load_tests` declaration or definition should be near the top of the
874
file so its effect can be seen.
880
We have a rich collection of tools to support writing tests. Please use
881
them in preference to ad-hoc solutions as they provide portability and
882
performance benefits.
885
TestCase and its subclasses
886
~~~~~~~~~~~~~~~~~~~~~~~~~~~
888
The ``bzrlib.tests`` module defines many TestCase classes to help you
892
A base TestCase that extends the Python standard library's
893
TestCase in several ways. TestCase is build on
894
``testtools.TestCase``, which gives it support for more assertion
895
methods (e.g. ``assertContainsRe``), ``addCleanup``, and other
896
features (see its API docs for details). It also has a ``setUp`` that
897
makes sure that global state like registered hooks and loggers won't
898
interfere with your test. All tests should use this base class
899
(whether directly or via a subclass). Note that we are trying not to
900
add more assertions at this point, and instead to build up a library
901
of ``bzrlib.tests.matchers``.
903
TestCaseWithMemoryTransport
904
Extends TestCase and adds methods like ``get_transport``,
905
``make_branch`` and ``make_branch_builder``. The files created are
906
stored in a MemoryTransport that is discarded at the end of the test.
907
This class is good for tests that need to make branches or use
908
transports, but that don't require storing things on disk. All tests
909
that create bzrdirs should use this base class (either directly or via
910
a subclass) as it ensures that the test won't accidentally operate on
911
real branches in your filesystem.
914
Extends TestCaseWithMemoryTransport. For tests that really do need
915
files to be stored on disk, e.g. because a subprocess uses a file, or
916
for testing functionality that accesses the filesystem directly rather
917
than via the Transport layer (such as dirstate).
919
TestCaseWithTransport
920
Extends TestCaseInTempDir. Provides ``get_url`` and
921
``get_readonly_url`` facilities. Subclasses can control the
922
transports used by setting ``vfs_transport_factory``,
923
``transport_server`` and/or ``transport_readonly_server``.
926
See the API docs for more details.
932
When writing a test for a feature, it is often necessary to set up a
933
branch with a certain history. The ``BranchBuilder`` interface allows the
934
creation of test branches in a quick and easy manner. Here's a sample
937
builder = self.make_branch_builder('relpath')
938
builder.build_commit()
939
builder.build_commit()
940
builder.build_commit()
941
branch = builder.get_branch()
943
``make_branch_builder`` is a method of ``TestCaseWithMemoryTransport``.
945
Note that many current tests create test branches by inheriting from
946
``TestCaseWithTransport`` and using the ``make_branch_and_tree`` helper to
947
give them a ``WorkingTree`` that they can commit to. However, using the
948
newer ``make_branch_builder`` helper is preferred, because it can build
949
the changes in memory, rather than on disk. Tests that are explictly
950
testing how we work with disk objects should, of course, use a real
953
Please see bzrlib.branchbuilder for more details.
955
If you're going to examine the commit timestamps e.g. in a test for log
956
output, you should set the timestamp on the tree, rather than using fuzzy
963
The ``TreeBuilder`` interface allows the construction of arbitrary trees
964
with a declarative interface. A sample session might look like::
966
tree = self.make_branch_and_tree('path')
967
builder = TreeBuilder()
968
builder.start_tree(tree)
969
builder.build(['foo', "bar/", "bar/file"])
970
tree.commit('commit the tree')
971
builder.finish_tree()
973
Usually a test will create a tree using ``make_branch_and_memory_tree`` (a
974
method of ``TestCaseWithMemoryTransport``) or ``make_branch_and_tree`` (a
975
method of ``TestCaseWithTransport``).
977
Please see bzrlib.treebuilder for more details.
982
PreviewTrees are based on TreeTransforms. This means they can represent
983
virtually any state that a WorkingTree can have, including unversioned files.
984
They can be used to test the output of anything that produces TreeTransforms,
985
such as merge algorithms and revert. They can also be used to test anything
986
that takes arbitrary Trees as its input.
990
# Get an empty tree to base the transform on.
991
b = self.make_branch('.')
992
empty_tree = b.repository.revision_tree(_mod_revision.NULL_REVISION)
993
tt = TransformPreview(empty_tree)
994
self.addCleanup(tt.finalize)
995
# Empty trees don't have a root, so add it first.
996
root = tt.new_directory('', ROOT_PARENT, 'tree-root')
997
# Set the contents of a file.
998
tt.new_file('new-file', root, 'contents', 'file-id')
999
preview = tt.get_preview_tree()
1000
# Test the contents.
1001
self.assertEqual('contents', preview.get_file_text('file-id'))
1003
PreviewTrees can stack, with each tree falling back to the previous::
1005
tt2 = TransformPreview(preview)
1006
self.addCleanup(tt2.finalize)
1007
tt2.new_file('new-file2', tt2.root, 'contents2', 'file-id2')
1008
preview2 = tt2.get_preview_tree()
1009
self.assertEqual('contents', preview2.get_file_text('file-id'))
1010
self.assertEqual('contents2', preview2.get_file_text('file-id2'))
1013
Temporarily changing state
1014
~~~~~~~~~~~~~~~~~~~~~~~~~~
1016
If your test needs to temporarily mutate some global state, and you need
1017
it restored at the end, you can say for example::
1019
self.overrideAttr(osutils, '_cached_user_encoding', 'latin-1')
1021
This should be used with discretion; sometimes it's better to make the
1022
underlying code more testable so that you don't need to rely on monkey
1026
Observing calls to a function
1027
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1029
Sometimes it's useful to observe how a function is called, typically when
1030
calling it has side effects but the side effects are not easy to observe
1031
from a test case. For instance the function may be expensive and we want
1032
to assert it is not called too many times, or it has effects on the
1033
machine that are safe to run during a test but not easy to measure. In
1034
these cases, you can use `recordCalls` which will monkey-patch in a
1035
wrapper that records when the function is called.
1038
Temporarily changing environment variables
1039
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1041
If yout test needs to temporarily change some environment variable value
1042
(which generally means you want it restored at the end), you can use::
1044
self.overrideEnv('BZR_ENV_VAR', 'new_value')
1046
If you want to remove a variable from the environment, you should use the
1047
special ``None`` value::
1049
self.overrideEnv('PATH', None)
1051
If you add a new feature which depends on a new environment variable, make
1052
sure it behaves properly when this variable is not defined (if applicable) and
1053
if you need to enforce a specific default value, check the
1054
``TestCase._cleanEnvironment`` in ``bzrlib.tests.__init__.py`` which defines a
1055
proper set of values for all tests.
1060
Our base ``TestCase`` class provides an ``addCleanup`` method, which
1061
should be used instead of ``tearDown``. All the cleanups are run when the
1062
test finishes, regardless of whether it passes or fails. If one cleanup
1063
fails, later cleanups are still run.
1065
(The same facility is available outside of tests through
1066
``bzrlib.cleanup``.)
1072
Generally we prefer automated testing but sometimes a manual test is the
1073
right thing, especially for performance tests that want to measure elapsed
1074
time rather than effort.
1076
Simulating slow networks
1077
------------------------
1079
To get realistically slow network performance for manually measuring
1080
performance, we can simulate 500ms latency (thus 1000ms round trips)::
1082
$ sudo tc qdisc add dev lo root netem delay 500ms
1084
Normal system behaviour is restored with ::
1086
$ sudo tc qdisc del dev lo root
1088
A more precise version that only filters traffic to port 4155 is::
1090
tc qdisc add dev lo root handle 1: prio
1091
tc qdisc add dev lo parent 1:3 handle 30: netem delay 500ms
1092
tc qdisc add dev lo parent 30:1 handle 40: prio
1093
tc filter add dev lo protocol ip parent 1:0 prio 3 u32 match ip dport 4155 0xffff flowid 1:3 handle 800::800
1094
tc filter add dev lo protocol ip parent 1:0 prio 3 u32 match ip sport 4155 0xffff flowid 1:3 handle 800::801
1096
and to remove this::
1098
tc filter del dev lo protocol ip parent 1: pref 3 u32
1099
tc qdisc del dev lo root handle 1:
1101
You can use similar code to add additional delay to a real network
1102
interface, perhaps only when talking to a particular server or pointing at
1103
a VM. For more information see <http://lartc.org/>.
1106
.. |--| unicode:: U+2014
1109
vim: ft=rst tw=74 ai et sw=4
added
removed
doc/developers/testing.txt
