Writing Python Tests

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Revision as of 12:34, 7 July 2018 by Slowfranklin (talk | contribs)

Use Python as the first choice

Samba provides extensive Python bindings and test infrastructure, so if possible please write tests in Python as a first choice. Python provides exceptions and early returns, ensuring that subsequent code doesn't run after prerequisite checks have failed, many helper functions as well as setUp() and tearDown() routines allowing unit tests to be easily built.

Writing Python Tests for Samba


Python unittest.TestCase is the standard basis on which all of Samba's python based tests should be written.

This provides helpful routines such as assertTrue() etc, which provide a cosnsitent pattern in the tests.


Samba's subclass samba.tests.TestCase, provides additional helper routines such as env_loadparm()


You can explore the methods provided using pydoc:

PYTHONPATH=bin/python pydoc samba.tests.TestCase

Testing Samba binaries

When testing Samba binaries, please use:


Obtaining credentials for a sub process

A pattern like this is typical for passing credentials to a subprocess

creds = self.get_credentials()
cmd_line_auth = "-U%s/%s%%%s" % (creds.get_domain(),
                                 creds.get_username(), creds.get_password())

Running the subprocess

Use self.check_run or self.check_output

self.check_run("ndrdump samr samr_CreateUser in %s" % (self.data_path("samr-CreateUser-in.dat")))

Testing samba-tool

samba-tool is a special case, as it is written in python. To avoid a fork()/exec() of python from python, use


The runcmd() and runsubcmd() methods allows testing of a samba-tool command in the same process, which also allows the use of


This example from source4/torture/drs/python/fsmo.py shows how to run an authenticated subcommand without forcing a new kinit:

ccache_name = self.get_creds_ccache_name()
cmd_line_auth = "--krb5-ccache=%s" % ccache_name
(result, out, err) = self.runsubcmd("fsmo", "transfer",
                                    "--role=%s" % role,
                                    "-H", "ldap://%s:389" % DC,

Temporary directories

If you need a temp dir, use






descend from this class, so the self.tempdir attribute is available with a temporary directory. The framework will assert that directory is empty when the test is done.

Good Patterns

Where to add new tests

Samba Tests are scattered around the code. However, in general, unless already related to or derived from other tests, new tests should be added in


use subunitrun

Tests should be run using subunitrun if possible, declared in tests.py via planpythontestsuite(), not planoldpythontestsuite()

Avoid innovation

Try not to make your new test special. The more our tests look like each other, the easier it is for new developers to follow the same patterns.

Mysterious error messages

AttributeError: 'module' object has no attribute 'foo'

A traceback that ends like this:

Traceback (most recent call last):
  File "bin/python/samba/subunit/run.py", line 603, in createTests
  File "/usr/lib/python2.7/unittest/loader.py", line 130, in loadTestsFromNames
    suites = [self.loadTestsFromName(name, module) for name in names]
  File "/usr/lib/python2.7/unittest/loader.py", line 100, in loadTestsFromName
    parent, obj = obj, getattr(obj, part)
AttributeError: 'module' object has no attribute 'foo'

usually means there was an exception raised when the test framework was importing your foo.py test module. This means an error at the module's top level, or a syntax error in compilation, not an error in the actual tests (which are not run at this stage).

If the test runs fine for you locally but not in autobuild, the problem could be an ImportError, caused by the use of a module that is not in the Python standard library. If the module is in Samba's thirdparty directory, make sure you use this pattern:

import samba
samba.ensure_third_party_module("dns", "dnspython")
import dns.resolver

Debugging Python tests

Python tests that use subunit can be run directly by executing:

PYTHONPATH=bin/python python source4/scripting/bin/subunitrun TEST


PYTHONPATH=bin/python python source4/scripting/bin/subunitrun samba.tests.docs