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
333
make our documentation testable, rather than as a way to make tests.
335
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
337
__ http://docs.python.org/lib/module-doctest.html
343
``bzrlib/tests/script.py`` allows users to write tests in a syntax very close to a shell session,
344
using a restricted and limited set of commands that should be enough to mimic
345
most of the behaviours.
347
A script is a set of commands, each command is composed of:
349
* one mandatory command line,
350
* one optional set of input lines to feed the command,
351
* one optional set of output expected lines,
352
* one optional set of error expected lines.
354
Input, output and error lines can be specified in any order.
356
Except for the expected output, all lines start with a special
357
string (based on their origin when used under a Unix shell):
359
* '$ ' for the command,
361
* nothing for output,
364
Comments can be added anywhere, they start with '#' and end with
367
The execution stops as soon as an expected output or an expected error is not
370
When no output is specified, any ouput from the command is accepted
371
and execution continue.
373
If an error occurs and no expected error is specified, the execution stops.
375
An error is defined by a returned status different from zero, not by the
376
presence of text on the error stream.
378
The matching is done on a full string comparison basis unless '...' is used, in
379
which case expected output/errors can be less precise.
383
The following will succeeds only if 'bzr add' outputs 'adding file'::
388
If you want the command to succeed for any output, just use::
392
The following will stop with an error::
396
If you want it to succeed, use::
399
2> bzr: ERROR: unknown command "not-a-command"
401
You can use ellipsis (...) to replace any piece of text you don't want to be
404
$ bzr branch not-a-branch
405
2>bzr: ERROR: Not a branch...not-a-branch/".
407
This can be used to ignore entire lines too::
413
# And here we explain that surprising fourth line
420
You can check the content of a file with cat::
425
You can also check the existence of a file with cat, the following will fail if
426
the file doesn't exist::
430
The actual use of ScriptRunner within a TestCase looks something like
433
from bzrlib.tests import script
435
def test_unshelve_keep(self):
437
script.run_script(self, '''
439
$ bzr shelve --all -m Foo
442
$ bzr unshelve --keep
449
You can also test commands that read user interaction::
451
def test_confirm_action(self):
452
"""You can write tests that demonstrate user confirmation"""
453
commands.builtin_command_registry.register(cmd_test_confirm)
454
self.addCleanup(commands.builtin_command_registry.remove, 'test-confirm')
457
2>Really do it? [y/n]:
465
`bzrlib.tests.test_import_tariff` has some tests that measure how many
466
Python modules are loaded to run some representative commands.
468
We want to avoid loading code unnecessarily, for reasons including:
470
* Python modules are interpreted when they're loaded, either to define
471
classes or modules or perhaps to initialize some structures.
473
* With a cold cache we may incur blocking real disk IO for each module.
475
* Some modules depend on many others.
477
* Some optional modules such as `testtools` are meant to be soft
478
dependencies and only needed for particular cases. If they're loaded in
479
other cases then bzr may break for people who don't have those modules.
481
`test_import_tariff` allows us to check that removal of imports doesn't
484
This is done by running the command in a subprocess with
485
``--profile-imports``. Starting a whole Python interpreter is pretty
486
slow, so we don't want exhaustive testing here, but just enough to guard
487
against distinct fixed problems.
489
Assertions about precisely what is loaded tend to be brittle so we instead
490
make assertions that particular things aren't loaded.
492
Unless selftest is run with ``--no-plugins``, modules will be loaded in
493
the usual way and checks made on what they cause to be loaded. This is
494
probably worth checking into, because many bzr users have at least some
495
plugins installed (and they're included in binary installers).
497
In theory, plugins might have a good reason to load almost anything:
498
someone might write a plugin that opens a network connection or pops up a
499
gui window every time you run 'bzr status'. However, it's more likely
500
that the code to do these things is just being loaded accidentally. We
501
might eventually need to have a way to make exceptions for particular
504
Some things to check:
506
* non-GUI commands shouldn't load GUI libraries
508
* operations on bzr native formats sholudn't load foreign branch libraries
510
* network code shouldn't be loaded for purely local operations
512
* particularly expensive Python built-in modules shouldn't be loaded
513
unless there is a good reason
516
Testing locking behaviour
517
-------------------------
519
In order to test the locking behaviour of commands, it is possible to install
520
a hook that is called when a write lock is: acquired, released or broken.
521
(Read locks also exist, they cannot be discovered in this way.)
523
A hook can be installed by calling bzrlib.lock.Lock.hooks.install_named_hook.
524
The three valid hooks are: `lock_acquired`, `lock_released` and `lock_broken`.
531
lock.Lock.hooks.install_named_hook('lock_acquired',
532
locks_acquired.append, None)
533
lock.Lock.hooks.install_named_hook('lock_released',
534
locks_released.append, None)
536
`locks_acquired` will now receive a LockResult instance for all locks acquired
537
since the time the hook is installed.
539
The last part of the `lock_url` allows you to identify the type of object that is locked.
541
- BzrDir: `/branch-lock`
542
- Working tree: `/checkout/lock`
543
- Branch: `/branch/lock`
544
- Repository: `/repository/lock`
546
To test if a lock is a write lock on a working tree, one can do the following::
548
self.assertEndsWith(locks_acquired[0].lock_url, "/checkout/lock")
550
See bzrlib/tests/commands/test_revert.py for an example of how to use this for
557
In our enhancements to unittest we allow for some addition results beyond
558
just success or failure.
560
If a test can't be run, it can say that it's skipped by raising a special
561
exception. This is typically used in parameterized tests |--| for example
562
if a transport doesn't support setting permissions, we'll skip the tests
563
that relating to that. ::
566
return self.branch_format.initialize(repo.bzrdir)
567
except errors.UninitializableFormat:
568
raise tests.TestSkipped('Uninitializable branch format')
570
Raising TestSkipped is a good idea when you want to make it clear that the
571
test was not run, rather than just returning which makes it look as if it
574
Several different cases are distinguished:
577
Generic skip; the only type that was present up to bzr 0.18.
580
The test doesn't apply to the parameters with which it was run.
581
This is typically used when the test is being applied to all
582
implementations of an interface, but some aspects of the interface
583
are optional and not present in particular concrete
584
implementations. (Some tests that should raise this currently
585
either silently return or raise TestSkipped.) Another option is
586
to use more precise parameterization to avoid generating the test
590
The test can't be run because a dependency (typically a Python
591
library) is not available in the test environment. These
592
are in general things that the person running the test could fix
593
by installing the library. It's OK if some of these occur when
594
an end user runs the tests or if we're specifically testing in a
595
limited environment, but a full test should never see them.
597
See `Test feature dependencies`_ below.
600
The test exists but is known to fail, for example this might be
601
appropriate to raise if you've committed a test for a bug but not
602
the fix for it, or if something works on Unix but not on Windows.
604
Raising this allows you to distinguish these failures from the
605
ones that are not expected to fail. If the test would fail
606
because of something we don't expect or intend to fix,
607
KnownFailure is not appropriate, and TestNotApplicable might be
610
KnownFailure should be used with care as we don't want a
611
proliferation of quietly broken tests.
615
We plan to support three modes for running the test suite to control the
616
interpretation of these results. Strict mode is for use in situations
617
like merges to the mainline and releases where we want to make sure that
618
everything that can be tested has been tested. Lax mode is for use by
619
developers who want to temporarily tolerate some known failures. The
620
default behaviour is obtained by ``bzr selftest`` with no options, and
621
also (if possible) by running under another unittest harness.
623
======================= ======= ======= ========
624
result strict default lax
625
======================= ======= ======= ========
626
TestSkipped pass pass pass
627
TestNotApplicable pass pass pass
628
UnavailableFeature fail pass pass
629
KnownFailure fail pass pass
630
======================= ======= ======= ========
633
Test feature dependencies
634
-------------------------
636
Writing tests that require a feature
637
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
639
Rather than manually checking the environment in each test, a test class
640
can declare its dependence on some test features. The feature objects are
641
checked only once for each run of the whole test suite.
643
(For historical reasons, as of May 2007 many cases that should depend on
644
features currently raise TestSkipped.)
648
class TestStrace(TestCaseWithTransport):
650
_test_needs_features = [StraceFeature]
652
This means all tests in this class need the feature. If the feature is
653
not available the test will be skipped using UnavailableFeature.
655
Individual tests can also require a feature using the ``requireFeature``
658
self.requireFeature(StraceFeature)
660
The old naming style for features is CamelCase, but because they're
661
actually instances not classses they're now given instance-style names
664
Features already defined in ``bzrlib.tests`` and ``bzrlib.tests.features``
672
- UnicodeFilenameFeature
674
- CaseInsensitiveFilesystemFeature.
675
- chown_feature: The test can rely on OS being POSIX and python
677
- posix_permissions_feature: The test can use POSIX-style
678
user/group/other permission bits.
681
Defining a new feature that tests can require
682
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
684
New features for use with ``_test_needs_features`` or ``requireFeature``
685
are defined by subclassing ``bzrlib.tests.Feature`` and overriding the
686
``_probe`` and ``feature_name`` methods. For example::
688
class _SymlinkFeature(Feature):
691
return osutils.has_symlinks()
693
def feature_name(self):
696
SymlinkFeature = _SymlinkFeature()
698
A helper for handling running tests based on whether a python
699
module is available. This can handle 3rd-party dependencies (is
700
``paramiko`` available?) as well as stdlib (``termios``) or
701
extension modules (``bzrlib._groupcompress_pyx``). You create a
702
new feature instance with::
704
# in bzrlib/tests/features.py
705
apport = tests.ModuleAvailableFeature('apport')
708
# then in bzrlib/tests/test_apport.py
709
class TestApportReporting(TestCaseInTempDir):
711
_test_needs_features = [features.apport]
714
Testing exceptions and errors
715
-----------------------------
717
It's important to test handling of errors and exceptions. Because this
718
code is often not hit in ad-hoc testing it can often have hidden bugs --
719
it's particularly common to get NameError because the exception code
720
references a variable that has since been renamed.
722
.. TODO: Something about how to provoke errors in the right way?
724
In general we want to test errors at two levels:
726
1. A test in ``test_errors.py`` checking that when the exception object is
727
constructed with known parameters it produces an expected string form.
728
This guards against mistakes in writing the format string, or in the
729
``str`` representations of its parameters. There should be one for
730
each exception class.
732
2. Tests that when an api is called in a particular situation, it raises
733
an error of the expected class. You should typically use
734
``assertRaises``, which in the Bazaar test suite returns the exception
735
object to allow you to examine its parameters.
737
In some cases blackbox tests will also want to check error reporting. But
738
it can be difficult to provoke every error through the commandline
739
interface, so those tests are only done as needed |--| eg in response to a
740
particular bug or if the error is reported in an unusual way(?) Blackbox
741
tests should mostly be testing how the command-line interface works, so
742
should only test errors if there is something particular to the cli in how
743
they're displayed or handled.
749
The Python ``warnings`` module is used to indicate a non-fatal code
750
problem. Code that's expected to raise a warning can be tested through
753
The test suite can be run with ``-Werror`` to check no unexpected errors
756
However, warnings should be used with discretion. It's not an appropriate
757
way to give messages to the user, because the warning is normally shown
758
only once per source line that causes the problem. You should also think
759
about whether the warning is serious enought that it should be visible to
760
users who may not be able to fix it.
763
Interface implementation testing and test scenarios
764
---------------------------------------------------
766
There are several cases in Bazaar of multiple implementations of a common
767
conceptual interface. ("Conceptual" because it's not necessary for all
768
the implementations to share a base class, though they often do.)
769
Examples include transports and the working tree, branch and repository
772
In these cases we want to make sure that every implementation correctly
773
fulfils the interface requirements. For example, every Transport should
774
support the ``has()`` and ``get()`` and ``clone()`` methods. We have a
775
sub-suite of tests in ``test_transport_implementations``. (Most
776
per-implementation tests are in submodules of ``bzrlib.tests``, but not
777
the transport tests at the moment.)
779
These tests are repeated for each registered Transport, by generating a
780
new TestCase instance for the cross product of test methods and transport
781
implementations. As each test runs, it has ``transport_class`` and
782
``transport_server`` set to the class it should test. Most tests don't
783
access these directly, but rather use ``self.get_transport`` which returns
784
a transport of the appropriate type.
786
The goal is to run per-implementation only the tests that relate to that
787
particular interface. Sometimes we discover a bug elsewhere that happens
788
with only one particular transport. Once it's isolated, we can consider
789
whether a test should be added for that particular implementation,
790
or for all implementations of the interface.
792
The multiplication of tests for different implementations is normally
793
accomplished by overriding the ``load_tests`` function used to load tests
794
from a module. This function typically loads all the tests, then applies
795
a TestProviderAdapter to them, which generates a longer suite containing
796
all the test variations.
798
See also `Per-implementation tests`_ (above).
804
Some utilities are provided for generating variations of tests. This can
805
be used for per-implementation tests, or other cases where the same test
806
code needs to run several times on different scenarios.
808
The general approach is to define a class that provides test methods,
809
which depend on attributes of the test object being pre-set with the
810
values to which the test should be applied. The test suite should then
811
also provide a list of scenarios in which to run the tests.
813
Typically ``multiply_tests_from_modules`` should be called from the test
814
module's ``load_tests`` function.
820
We have a rich collection of tools to support writing tests. Please use
821
them in preference to ad-hoc solutions as they provide portability and
822
performance benefits.
825
TestCase and its subclasses
826
~~~~~~~~~~~~~~~~~~~~~~~~~~~
828
The ``bzrlib.tests`` module defines many TestCase classes to help you
832
A base TestCase that extends the Python standard library's
833
TestCase in several ways. TestCase is build on
834
``testtools.TestCase``, which gives it support for more assertion
835
methods (e.g. ``assertContainsRe``), ``addCleanup``, and other
836
features (see its API docs for details). It also has a ``setUp`` that
837
makes sure that global state like registered hooks and loggers won't
838
interfere with your test. All tests should use this base class
839
(whether directly or via a subclass). Note that we are trying not to
840
add more assertions at this point, and instead to build up a library
841
of ``bzrlib.tests.matchers``.
843
TestCaseWithMemoryTransport
844
Extends TestCase and adds methods like ``get_transport``,
845
``make_branch`` and ``make_branch_builder``. The files created are
846
stored in a MemoryTransport that is discarded at the end of the test.
847
This class is good for tests that need to make branches or use
848
transports, but that don't require storing things on disk. All tests
849
that create bzrdirs should use this base class (either directly or via
850
a subclass) as it ensures that the test won't accidentally operate on
851
real branches in your filesystem.
854
Extends TestCaseWithMemoryTransport. For tests that really do need
855
files to be stored on disk, e.g. because a subprocess uses a file, or
856
for testing functionality that accesses the filesystem directly rather
857
than via the Transport layer (such as dirstate).
859
TestCaseWithTransport
860
Extends TestCaseInTempDir. Provides ``get_url`` and
861
``get_readonly_url`` facilities. Subclasses can control the
862
transports used by setting ``vfs_transport_factory``,
863
``transport_server`` and/or ``transport_readonly_server``.
866
See the API docs for more details.
872
When writing a test for a feature, it is often necessary to set up a
873
branch with a certain history. The ``BranchBuilder`` interface allows the
874
creation of test branches in a quick and easy manner. Here's a sample
877
builder = self.make_branch_builder('relpath')
878
builder.build_commit()
879
builder.build_commit()
880
builder.build_commit()
881
branch = builder.get_branch()
883
``make_branch_builder`` is a method of ``TestCaseWithMemoryTransport``.
885
Note that many current tests create test branches by inheriting from
886
``TestCaseWithTransport`` and using the ``make_branch_and_tree`` helper to
887
give them a ``WorkingTree`` that they can commit to. However, using the
888
newer ``make_branch_builder`` helper is preferred, because it can build
889
the changes in memory, rather than on disk. Tests that are explictly
890
testing how we work with disk objects should, of course, use a real
893
Please see bzrlib.branchbuilder for more details.
895
If you're going to examine the commit timestamps e.g. in a test for log
896
output, you should set the timestamp on the tree, rather than using fuzzy
903
The ``TreeBuilder`` interface allows the construction of arbitrary trees
904
with a declarative interface. A sample session might look like::
906
tree = self.make_branch_and_tree('path')
907
builder = TreeBuilder()
908
builder.start_tree(tree)
909
builder.build(['foo', "bar/", "bar/file"])
910
tree.commit('commit the tree')
911
builder.finish_tree()
913
Usually a test will create a tree using ``make_branch_and_memory_tree`` (a
914
method of ``TestCaseWithMemoryTransport``) or ``make_branch_and_tree`` (a
915
method of ``TestCaseWithTransport``).
917
Please see bzrlib.treebuilder for more details.
920
Temporarily changing state
921
~~~~~~~~~~~~~~~~~~~~~~~~~~
923
If your test needs to temporarily mutate some global state, and you need
924
it restored at the end, you can say for example::
926
self.overrideAttr(osutils, '_cached_user_encoding', 'latin-1')
931
Our base ``TestCase`` class provides an ``addCleanup`` method, which
932
should be used instead of ``tearDown``. All the cleanups are run when the
933
test finishes, regardless of whether it passes or fails. If one cleanup
934
fails, later cleanups are still run.
936
(The same facility is available outside of tests through
943
Generally we prefer automated testing but sometimes a manual test is the
944
right thing, especially for performance tests that want to measure elapsed
945
time rather than effort.
947
Simulating slow networks
948
------------------------
950
To get realistically slow network performance for manually measuring
951
performance, we can simulate 500ms latency (thus 1000ms round trips)::
953
$ sudo tc qdisc add dev lo root netem delay 500ms
955
Normal system behaviour is restored with ::
957
$ sudo tc qdisc del dev lo root
959
A more precise version that only filters traffic to port 4155 is::
961
tc qdisc add dev lo root handle 1: prio
962
tc qdisc add dev lo parent 1:3 handle 30: netem delay 500ms
963
tc qdisc add dev lo parent 30:1 handle 40: prio
964
tc filter add dev lo protocol ip parent 1:0 prio 3 u32 match ip dport 4155 0xffff flowid 1:3 handle 800::800
965
tc filter add dev lo protocol ip parent 1:0 prio 3 u32 match ip sport 4155 0xffff flowid 1:3 handle 800::801
969
tc filter del dev lo protocol ip parent 1: pref 3 u32
970
tc qdisc del dev lo root handle 1:
972
You can use similar code to add additional delay to a real network
973
interface, perhaps only when talking to a particular server or pointing at
974
a VM. For more information see <http://lartc.org/>.
977
.. |--| unicode:: U+2014
980
vim: ft=rst tw=74 ai et sw=4
added
removed
doc/developers/testing.txt
