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
189
Normally you should add or update a test for all bug fixes or new features
193
Where should I put a new test?
194
------------------------------
196
Bzrlib's tests are organised by the type of test. Most of the tests in
197
bzr's test suite belong to one of these categories:
200
- Blackbox (UI) tests
201
- Per-implementation tests
204
A quick description of these test types and where they belong in bzrlib's
205
source follows. Not all tests fall neatly into one of these categories;
206
in those cases use your judgement.
212
Unit tests make up the bulk of our test suite. These are tests that are
213
focused on exercising a single, specific unit of the code as directly
214
as possible. Each unit test is generally fairly short and runs very
217
They are found in ``bzrlib/tests/test_*.py``. So in general tests should
218
be placed in a file named test_FOO.py where FOO is the logical thing under
221
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
222
See bzrlib/tests/test_sampler.py for a template test script.
228
Tests can be written for the UI or for individual areas of the library.
229
Choose whichever is appropriate: if adding a new command, or a new command
230
option, then you should be writing a UI test. If you are both adding UI
231
functionality and library functionality, you will want to write tests for
232
both the UI and the core behaviours. We call UI tests 'blackbox' tests
233
and they belong in ``bzrlib/tests/blackbox/*.py``.
235
When writing blackbox tests please honour the following conventions:
237
1. Place the tests for the command 'name' in
238
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
239
to locate the test script for a faulty command.
241
2. Use the 'self.run_bzr("name")' utility function to invoke the command
242
rather than running bzr in a subprocess or invoking the
243
cmd_object.run() method directly. This is a lot faster than
244
subprocesses and generates the same logging output as running it in a
245
subprocess (which invoking the method directly does not).
247
3. Only test the one command in a single test script. Use the bzrlib
248
library when setting up tests and when evaluating the side-effects of
249
the command. We do this so that the library api has continual pressure
250
on it to be as functional as the command line in a simple manner, and
251
to isolate knock-on effects throughout the blackbox test suite when a
252
command changes its name or signature. Ideally only the tests for a
253
given command are affected when a given command is changed.
255
4. If you have a test which does actually require running bzr in a
256
subprocess you can use ``run_bzr_subprocess``. By default the spawned
257
process will not load plugins unless ``--allow-plugins`` is supplied.
260
Per-implementation tests
261
~~~~~~~~~~~~~~~~~~~~~~~~
263
Per-implementation tests are tests that are defined once and then run
264
against multiple implementations of an interface. For example,
265
``per_transport.py`` defines tests that all Transport implementations
266
(local filesystem, HTTP, and so on) must pass. They are found in
267
``bzrlib/tests/per_*/*.py``, and ``bzrlib/tests/per_*.py``.
269
These are really a sub-category of unit tests, but an important one.
271
Along the same lines are tests for extension modules. We generally have
272
both a pure-python and a compiled implementation for each module. As such,
273
we want to run the same tests against both implementations. These can
274
generally be found in ``bzrlib/tests/*__*.py`` since extension modules are
275
usually prefixed with an underscore. Since there are only two
276
implementations, we have a helper function
277
``bzrlib.tests.permute_for_extension``, which can simplify the
278
``load_tests`` implementation.
284
We make selective use of doctests__. In general they should provide
285
*examples* within the API documentation which can incidentally be tested. We
286
don't try to test every important case using doctests |--| regular Python
287
tests are generally a better solution. That is, we just use doctests to
288
make our documentation testable, rather than as a way to make tests.
290
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
292
__ http://docs.python.org/lib/module-doctest.html
298
``bzrlib/tests/script.py`` allows users to write tests in a syntax very close to a shell session,
299
using a restricted and limited set of commands that should be enough to mimic
300
most of the behaviours.
302
A script is a set of commands, each command is composed of:
304
* one mandatory command line,
305
* one optional set of input lines to feed the command,
306
* one optional set of output expected lines,
307
* one optional set of error expected lines.
309
Input, output and error lines can be specified in any order.
311
Except for the expected output, all lines start with a special
312
string (based on their origin when used under a Unix shell):
314
* '$ ' for the command,
316
* nothing for output,
319
Comments can be added anywhere, they start with '#' and end with
322
The execution stops as soon as an expected output or an expected error is not
325
When no output is specified, any ouput from the command is accepted
326
and execution continue.
328
If an error occurs and no expected error is specified, the execution stops.
330
An error is defined by a returned status different from zero, not by the
331
presence of text on the error stream.
333
The matching is done on a full string comparison basis unless '...' is used, in
334
which case expected output/errors can be less precise.
338
The following will succeeds only if 'bzr add' outputs 'adding file'::
343
If you want the command to succeed for any output, just use::
347
The following will stop with an error::
351
If you want it to succeed, use::
354
2> bzr: ERROR: unknown command "not-a-command"
356
You can use ellipsis (...) to replace any piece of text you don't want to be
359
$ bzr branch not-a-branch
360
2>bzr: ERROR: Not a branch...not-a-branch/".
362
This can be used to ignore entire lines too::
368
# And here we explain that surprising fourth line
375
You can check the content of a file with cat::
380
You can also check the existence of a file with cat, the following will fail if
381
the file doesn't exist::
385
The actual use of ScriptRunner within a TestCase looks something like
388
def test_unshelve_keep(self):
391
sr.run_script(self, '''
393
$ bzr shelve --all -m Foo
396
$ bzr unshelve --keep
407
`bzrlib.tests.test_import_tariff` has some tests that measure how many
408
Python modules are loaded to run some representative commands.
410
We want to avoid loading code unnecessarily, for reasons including:
412
* Python modules are interpreted when they're loaded, either to define
413
classes or modules or perhaps to initialize some structures.
415
* With a cold cache we may incur blocking real disk IO for each module.
417
* Some modules depend on many others.
419
* Some optional modules such as `testtools` are meant to be soft
420
dependencies and only needed for particular cases. If they're loaded in
421
other cases then bzr may break for people who don't have those modules.
423
`test_import_tarrif` allows us to check that removal of imports doesn't
426
This is done by running the command in a subprocess with
427
``--profile-imports``. Starting a whole Python interpreter is pretty
428
slow, so we don't want exhaustive testing here, but just enough to guard
429
against distinct fixed problems.
431
Assertions about precisely what is loaded tend to be brittle so we instead
432
make assertions that particular things aren't loaded.
434
Unless selftest is run with ``--no-plugins``, modules will be loaded in
435
the usual way and checks made on what they cause to be loaded. This is
436
probably worth checking into, because many bzr users have at least some
437
plugins installed (and they're included in binary installers).
439
In theory, plugins might have a good reason to load almost anything:
440
someone might write a plugin that opens a network connection or pops up a
441
gui window every time you run 'bzr status'. However, it's more likely
442
that the code to do these things is just being loaded accidentally. We
443
might eventually need to have a way to make exceptions for particular
446
Some things to check:
448
* non-GUI commands shouldn't load GUI libraries
450
* operations on bzr native formats sholudn't load foreign branch libraries
452
* network code shouldn't be loaded for purely local operations
454
* particularly expensive Python built-in modules shouldn't be loaded
455
unless there is a good reason
461
In our enhancements to unittest we allow for some addition results beyond
462
just success or failure.
464
If a test can't be run, it can say that it's skipped by raising a special
465
exception. This is typically used in parameterized tests |--| for example
466
if a transport doesn't support setting permissions, we'll skip the tests
467
that relating to that. ::
470
return self.branch_format.initialize(repo.bzrdir)
471
except errors.UninitializableFormat:
472
raise tests.TestSkipped('Uninitializable branch format')
474
Raising TestSkipped is a good idea when you want to make it clear that the
475
test was not run, rather than just returning which makes it look as if it
478
Several different cases are distinguished:
481
Generic skip; the only type that was present up to bzr 0.18.
484
The test doesn't apply to the parameters with which it was run.
485
This is typically used when the test is being applied to all
486
implementations of an interface, but some aspects of the interface
487
are optional and not present in particular concrete
488
implementations. (Some tests that should raise this currently
489
either silently return or raise TestSkipped.) Another option is
490
to use more precise parameterization to avoid generating the test
494
The test can't be run because a dependency (typically a Python
495
library) is not available in the test environment. These
496
are in general things that the person running the test could fix
497
by installing the library. It's OK if some of these occur when
498
an end user runs the tests or if we're specifically testing in a
499
limited environment, but a full test should never see them.
501
See `Test feature dependencies`_ below.
504
The test exists but is known to fail, for example this might be
505
appropriate to raise if you've committed a test for a bug but not
506
the fix for it, or if something works on Unix but not on Windows.
508
Raising this allows you to distinguish these failures from the
509
ones that are not expected to fail. If the test would fail
510
because of something we don't expect or intend to fix,
511
KnownFailure is not appropriate, and TestNotApplicable might be
514
KnownFailure should be used with care as we don't want a
515
proliferation of quietly broken tests.
519
We plan to support three modes for running the test suite to control the
520
interpretation of these results. Strict mode is for use in situations
521
like merges to the mainline and releases where we want to make sure that
522
everything that can be tested has been tested. Lax mode is for use by
523
developers who want to temporarily tolerate some known failures. The
524
default behaviour is obtained by ``bzr selftest`` with no options, and
525
also (if possible) by running under another unittest harness.
527
======================= ======= ======= ========
528
result strict default lax
529
======================= ======= ======= ========
530
TestSkipped pass pass pass
531
TestNotApplicable pass pass pass
532
UnavailableFeature fail pass pass
533
KnownFailure fail pass pass
534
======================= ======= ======= ========
537
Test feature dependencies
538
-------------------------
540
Writing tests that require a feature
541
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
543
Rather than manually checking the environment in each test, a test class
544
can declare its dependence on some test features. The feature objects are
545
checked only once for each run of the whole test suite.
547
(For historical reasons, as of May 2007 many cases that should depend on
548
features currently raise TestSkipped.)
552
class TestStrace(TestCaseWithTransport):
554
_test_needs_features = [StraceFeature]
556
This means all tests in this class need the feature. If the feature is
557
not available the test will be skipped using UnavailableFeature.
559
Individual tests can also require a feature using the ``requireFeature``
562
self.requireFeature(StraceFeature)
564
The old naming style for features is CamelCase, but because they're
565
actually instances not classses they're now given instance-style names
568
Features already defined in ``bzrlib.tests`` and ``bzrlib.tests.features``
576
- UnicodeFilenameFeature
578
- CaseInsensitiveFilesystemFeature.
579
- ChownFeature: The test can rely on OS being POSIX and python
583
Defining a new feature that tests can require
584
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
586
New features for use with ``_test_needs_features`` or ``requireFeature``
587
are defined by subclassing ``bzrlib.tests.Feature`` and overriding the
588
``_probe`` and ``feature_name`` methods. For example::
590
class _SymlinkFeature(Feature):
593
return osutils.has_symlinks()
595
def feature_name(self):
598
SymlinkFeature = _SymlinkFeature()
600
A helper for handling running tests based on whether a python
601
module is available. This can handle 3rd-party dependencies (is
602
``paramiko`` available?) as well as stdlib (``termios``) or
603
extension modules (``bzrlib._groupcompress_pyx``). You create a
604
new feature instance with::
606
# in bzrlib/tests/features.py
607
apport = tests.ModuleAvailableFeature('apport')
610
# then in bzrlib/tests/test_apport.py
611
class TestApportReporting(TestCaseInTempDir):
613
_test_needs_features = [features.apport]
616
Testing exceptions and errors
617
-----------------------------
619
It's important to test handling of errors and exceptions. Because this
620
code is often not hit in ad-hoc testing it can often have hidden bugs --
621
it's particularly common to get NameError because the exception code
622
references a variable that has since been renamed.
624
.. TODO: Something about how to provoke errors in the right way?
626
In general we want to test errors at two levels:
628
1. A test in ``test_errors.py`` checking that when the exception object is
629
constructed with known parameters it produces an expected string form.
630
This guards against mistakes in writing the format string, or in the
631
``str`` representations of its parameters. There should be one for
632
each exception class.
634
2. Tests that when an api is called in a particular situation, it raises
635
an error of the expected class. You should typically use
636
``assertRaises``, which in the Bazaar test suite returns the exception
637
object to allow you to examine its parameters.
639
In some cases blackbox tests will also want to check error reporting. But
640
it can be difficult to provoke every error through the commandline
641
interface, so those tests are only done as needed |--| eg in response to a
642
particular bug or if the error is reported in an unusual way(?) Blackbox
643
tests should mostly be testing how the command-line interface works, so
644
should only test errors if there is something particular to the cli in how
645
they're displayed or handled.
651
The Python ``warnings`` module is used to indicate a non-fatal code
652
problem. Code that's expected to raise a warning can be tested through
655
The test suite can be run with ``-Werror`` to check no unexpected errors
658
However, warnings should be used with discretion. It's not an appropriate
659
way to give messages to the user, because the warning is normally shown
660
only once per source line that causes the problem. You should also think
661
about whether the warning is serious enought that it should be visible to
662
users who may not be able to fix it.
665
Interface implementation testing and test scenarios
666
---------------------------------------------------
668
There are several cases in Bazaar of multiple implementations of a common
669
conceptual interface. ("Conceptual" because it's not necessary for all
670
the implementations to share a base class, though they often do.)
671
Examples include transports and the working tree, branch and repository
674
In these cases we want to make sure that every implementation correctly
675
fulfils the interface requirements. For example, every Transport should
676
support the ``has()`` and ``get()`` and ``clone()`` methods. We have a
677
sub-suite of tests in ``test_transport_implementations``. (Most
678
per-implementation tests are in submodules of ``bzrlib.tests``, but not
679
the transport tests at the moment.)
681
These tests are repeated for each registered Transport, by generating a
682
new TestCase instance for the cross product of test methods and transport
683
implementations. As each test runs, it has ``transport_class`` and
684
``transport_server`` set to the class it should test. Most tests don't
685
access these directly, but rather use ``self.get_transport`` which returns
686
a transport of the appropriate type.
688
The goal is to run per-implementation only the tests that relate to that
689
particular interface. Sometimes we discover a bug elsewhere that happens
690
with only one particular transport. Once it's isolated, we can consider
691
whether a test should be added for that particular implementation,
692
or for all implementations of the interface.
694
The multiplication of tests for different implementations is normally
695
accomplished by overriding the ``load_tests`` function used to load tests
696
from a module. This function typically loads all the tests, then applies
697
a TestProviderAdapter to them, which generates a longer suite containing
698
all the test variations.
700
See also `Per-implementation tests`_ (above).
706
Some utilities are provided for generating variations of tests. This can
707
be used for per-implementation tests, or other cases where the same test
708
code needs to run several times on different scenarios.
710
The general approach is to define a class that provides test methods,
711
which depend on attributes of the test object being pre-set with the
712
values to which the test should be applied. The test suite should then
713
also provide a list of scenarios in which to run the tests.
715
Typically ``multiply_tests_from_modules`` should be called from the test
716
module's ``load_tests`` function.
722
We have a rich collection of tools to support writing tests. Please use
723
them in preference to ad-hoc solutions as they provide portability and
724
performance benefits.
727
TestCase and its subclasses
728
~~~~~~~~~~~~~~~~~~~~~~~~~~~
730
The ``bzrlib.tests`` module defines many TestCase classes to help you
734
A base TestCase that extends the Python standard library's
735
TestCase in several ways. It adds more assertion methods (e.g.
736
``assertContainsRe``), ``addCleanup``, and other features (see its API
737
docs for details). It also has a ``setUp`` that makes sure that
738
global state like registered hooks and loggers won't interfere with
739
your test. All tests should use this base class (whether directly or
742
TestCaseWithMemoryTransport
743
Extends TestCase and adds methods like ``get_transport``,
744
``make_branch`` and ``make_branch_builder``. The files created are
745
stored in a MemoryTransport that is discarded at the end of the test.
746
This class is good for tests that need to make branches or use
747
transports, but that don't require storing things on disk. All tests
748
that create bzrdirs should use this base class (either directly or via
749
a subclass) as it ensures that the test won't accidentally operate on
750
real branches in your filesystem.
753
Extends TestCaseWithMemoryTransport. For tests that really do need
754
files to be stored on disk, e.g. because a subprocess uses a file, or
755
for testing functionality that accesses the filesystem directly rather
756
than via the Transport layer (such as dirstate).
758
TestCaseWithTransport
759
Extends TestCaseInTempDir. Provides ``get_url`` and
760
``get_readonly_url`` facilities. Subclasses can control the
761
transports used by setting ``vfs_transport_factory``,
762
``transport_server`` and/or ``transport_readonly_server``.
765
See the API docs for more details.
771
When writing a test for a feature, it is often necessary to set up a
772
branch with a certain history. The ``BranchBuilder`` interface allows the
773
creation of test branches in a quick and easy manner. Here's a sample
776
builder = self.make_branch_builder('relpath')
777
builder.build_commit()
778
builder.build_commit()
779
builder.build_commit()
780
branch = builder.get_branch()
782
``make_branch_builder`` is a method of ``TestCaseWithMemoryTransport``.
784
Note that many current tests create test branches by inheriting from
785
``TestCaseWithTransport`` and using the ``make_branch_and_tree`` helper to
786
give them a ``WorkingTree`` that they can commit to. However, using the
787
newer ``make_branch_builder`` helper is preferred, because it can build
788
the changes in memory, rather than on disk. Tests that are explictly
789
testing how we work with disk objects should, of course, use a real
792
Please see bzrlib.branchbuilder for more details.
794
If you're going to examine the commit timestamps e.g. in a test for log
795
output, you should set the timestamp on the tree, rather than using fuzzy
802
The ``TreeBuilder`` interface allows the construction of arbitrary trees
803
with a declarative interface. A sample session might look like::
805
tree = self.make_branch_and_tree('path')
806
builder = TreeBuilder()
807
builder.start_tree(tree)
808
builder.build(['foo', "bar/", "bar/file"])
809
tree.commit('commit the tree')
810
builder.finish_tree()
812
Usually a test will create a tree using ``make_branch_and_memory_tree`` (a
813
method of ``TestCaseWithMemoryTransport``) or ``make_branch_and_tree`` (a
814
method of ``TestCaseWithTransport``).
816
Please see bzrlib.treebuilder for more details.
819
.. |--| unicode:: U+2014
added
removed
doc/developers/testing.txt
