tl.testing - Utilities for writing tests¶
This package provides various utilities that can be used when writing tests. It is compatible to Python versions 2.6 and 2.7.
Sandboxes of directories and files¶
When testing code that modifies directories and files, it is useful to be able
to create and inspect a sample tree of directories and files easily. The
tl.testing.fs
module provides support for creating a tree from a textual
description, listing it in the same format and clean up after itself.
In a doc test, these facilities might be used like this to create and list a directory, a file and a symbolic link:
>>> from tl.testing.fs import new_sandbox, ls
>>> new_sandbox("""\
... d foo
... f foo/bar asdf
... l baz -> foo/bar
... """)
>>> ls()
l baz -> foo/bar
d foo
f foo/bar asdf
See the file fs.txt
found with the source code for further advice,
including how to set up and tear down tests using file-system sandboxes.
Installing callable scripts¶
Some functionality one might want to test makes use of external programs such
as a pager or a text editor. The tl.testing.script
module provides
utilities that install simple mock scripts in places where the code to be
tested will find them. They take a string of Python code and create a wrapper
script that sets the Python path to match that of the test and runs the code.
This is how such a mock script might be used in a doc test:
>>> from tl.testing.script import install
>>> script_path = install("print 'A simple script.'")
>>> print open(script_path).read()
#!...
import sys
sys.path[:] = [...]
print 'A simple script.'
>>> import subprocess
>>> sub = subprocess.Popen(script_path, shell=True, stdout=subprocess.PIPE)
>>> stdout, stderr = sub.communicate()
>>> print stdout
A simple script.
See the file script.txt
found with the source code for further
possibilities how to install and access mock scripts as well as how to tear
down tests using mock scripts.
Doc-testing the graphical content of cairo surfaces¶
While it is straight-forward to compare the content of two cairo surfaces in Python code, handling graphics is beyond doc tests. However, the manuel package can be used to extract more general test cases from a text document while allowing to mix them with doc tests in a natural way.
The tl.testing.cairo
module provides a test suite factory that uses manuel
to execute graphical tests formulated as restructured-text figures. The
caption of such a figure is supposed to be a literal Python expression whose
value is a cairo surface, and its image is used as the test expectation.
This is how a surface might be compared to an expected image in a doc test:
>>> import cairo
>>> from pkg_resources import resource_filename
>>> image = resource_filename('tl.testing', 'testimages/correct.png')
.. figure:: tl/testing/testimages/correct.png
``cairo.ImageSurface.create_from_png(image)``
See the file cairo.txt
found with the source code for further advice and
documentation of the possible test output.
Working with threads in test code¶
The standard TestCase
class doesn’t collect errors and failures that
occurred in other threads than the main one. The tl.testing.thread
module
provides thread classes and a ThreadAwareTestCase
class to allow just
that, as well as some other conveniences for tests that deal with threads:
preventing expected unhandled exceptions in threads from being printed with
the test output, reporting threads left behind by a test, running code in a
daemon thread, joining threads and counting the threads started during the
test’s run time:
>>> import time
>>> import tl.testing.thread
>>> class SampleTest(tl.testing.thread.ThreadAwareTestCase):
...
... def test_error_in_thread_should_be_reported(self):
... with tl.testing.thread.ThreadJoiner(1):
... self.run_in_thread(lambda: 1/0)
...
... def test_active_count_should_count_only_new_threads(self):
... with tl.testing.thread.ThreadJoiner(1):
... self.run_in_thread(lambda: time.sleep(0.1))
... self.assertEqual(1, self.active_count())
... self.assertEqual(0, self.active_count())
>>> import unittest
>>> run(unittest.makeSuite(SampleTest))
======================================================================
ERROR: test_error_in_thread_should_be_reported (__builtin__.SampleTest)
----------------------------------------------------------------------
Traceback (most recent call last):
...
ZeroDivisionError: integer division or modulo by zero
----------------------------------------------------------------------
Ran 2 tests in N.NNNs
FAILED (errors=1)
See the file thread.txt
found with the source code for further details of
the ThreadAwareTestCase
class.
Constructing test suites that use manuel¶
As manuel
provides some powerful features in addition to standard
doctests, manuel test suites are set up slightly differently from standard
ones. The tl.testing.doctest
module implements a DocFileSuite
factory
that can be used like the standard one but creates a test suite using manuel
and allows some additional configuration related to manuel, among them the
ability to interpret footnotes that used to be done using the deprecated
zope.testing.doctest
:
>>> sample_txt = write('sample.txt', """\
... [#footnote]_
... >>> x
... 1
...
... .. [#footnote]
... >>> x = 1
... """)
>>> from tl.testing.doctest import DocFileSuite
>>> run(DocFileSuite(sample_txt, footnotes=True))
----------------------------------------------------------------------
Ran 1 test in N.NNNs
OK
>>> sample_txt = write('sample.txt', """\
... .. code-block:: python
... x = 1
...
... >>> x
... 1
... """)
>>> import manuel.codeblock
>>> run(DocFileSuite(sample_txt, manuel=manuel.codeblock.Manuel()))
----------------------------------------------------------------------
Ran 1 test in N.NNNs
OK