Stack-based test setUp and tearDown¶
Writing doctest
setUp
and tearDown
functions can be a bit tedious,
especially when setUp/tearDown functions are combined. This is also
true of unittest.TestCase
tests. The zope.testing.setupstack
eases
the tedium for both types of tests.
The zope.testing.setupstack
module provides a small framework for
automating test tear down. It provides a generic tearDown
function that
calls the registered
functions (in reverse order); there
is no need for special setup code.
To see how this works we’ll create a faux test:
>>> class Test:
... def __init__(self):
... self.globs = {}
>>> test = Test()
We’ll register some tearDown
functions that just print something:
>>> import sys
>>> import zope.testing.setupstack
>>> zope.testing.setupstack.register(
... test, lambda : sys.stdout.write('td 1\n'))
>>> zope.testing.setupstack.register(
... test, lambda : sys.stdout.write('td 2\n'))
Now, when we call the tearDown
function:
>>> zope.testing.setupstack.tearDown(test)
td 2
td 1
The registered tearDown functions are run. Note that they are run in the reverse order that they were registered.
Extra positional arguments can be passed to register
:
>>> zope.testing.setupstack.register(
... test, lambda x, y, z: sys.stdout.write('%s %s %s\n' % (x, y, z)),
... 1, 2, z=9)
>>> zope.testing.setupstack.tearDown(test)
1 2 9
Temporary Test Directory¶
Often, tests create files as they demonstrate functionality. They need to arrange for the removeal of these files when the test is cleaned up.
The setUpDirectory
function automates this. We’ll get the current
directory first:
>>> import os
>>> here = os.getcwd()
We’ll also create a new test:
>>> test = Test()
Now we’ll call the setUpDirectory
function:
>>> zope.testing.setupstack.setUpDirectory(test)
Now the current working directory has changed:
>>> here == os.getcwd()
False
>>> setupstack_cwd = os.getcwd()
We can create files to out heart’s content:
>>> with open('Data.fs', 'w') as f:
... foo = f.write('xxx')
>>> os.path.exists(os.path.join(setupstack_cwd, 'Data.fs'))
True
We’ll make the file read-only. This can cause problems on Windows, but setupstack takes care of that by making files writable before trying to remove them.
>>> import stat
>>> os.chmod('Data.fs', stat.S_IREAD)
On Unix systems, broken symlinks can cause problems because the chmod attempt by the teardown hook will fail; let’s set up a broken symlink as well, and verify the teardown doesn’t break because of that:
>>> if sys.platform != 'win32':
... os.symlink('NotThere', 'BrokenLink')
When tearDown
is called:
>>> zope.testing.setupstack.tearDown(test)
We’ll be back where we started:
>>> here == os.getcwd()
True
and the files we created will be gone (along with the temporary directory that was created:
>>> os.path.exists(os.path.join(setupstack_cwd, 'Data.fs'))
False
Context-manager support¶
You can leverage context managers using the contextmanager
method.
The result of calling the content manager’s __enter__
method will be
returned. The context-manager’s __exit__
method will be called as part
of test tear down:
>>> class Manager(object):
... def __init__(self, *args, **kw):
... if kw:
... args += (kw, )
... self.args = args
... def __enter__(self):
... print_('enter', *self.args)
... return 42
... def __exit__(self, *args):
... print_('exit', args, *self.args)
>>> manager = Manager()
>>> test = Test()
>>> zope.testing.setupstack.context_manager(test, manager)
enter
42
>>> zope.testing.setupstack.tearDown(test)
exit (None, None, None)
By far the most commonly called context manager is unittest.mock.patch
, so
there’s a convenience function to make that simpler:
>>> zope.testing.setupstack.mock(test, 'time.time', return_value=42)
enter time.time {'return_value': 42}
42
>>> zope.testing.setupstack.tearDown(test)
exit (None, None, None) time.time {'return_value': 42}
globs¶
Doctests have globs
attributes used to hold test globals.
setupstack
was originally designed to work with doctests, but can
now work with either doctests, or other test objects, as long as the
test objects have either a globs
attribute or a __dict__
attribute. The zope.testing.setupstack.globs
function is used to
get the globals for a test object:
>>> zope.testing.setupstack.globs(test) is test.globs
True
Here, because the test object had a globs
attribute, it was
returned. Because we used the test object above, it has a setupstack:
>>> '__zope.testing.setupstack' in test.globs
True
If we remove the globs
attribute, the object’s instance dictionary
will be used:
>>> del test.globs
>>> zope.testing.setupstack.globs(test) is test.__dict__
True
>>> zope.testing.setupstack.context_manager(test, manager)
enter
42
>>> '__zope.testing.setupstack' in test.__dict__
True
The globs
function is used internally, but can also be used by
setup code to support either doctests or other test objects.
TestCase¶
A TestCase
class is provided that:
Makes it easier to call setupstack apis, and
provides an inheritable
tearDown
method.
In addition to a tearDown
method, the class provides methods:
setupDirectory()
Creates a temporary directory, runs the test, and cleans it up.
register(func)
Register a tear-down function.
context_manager(manager)
Enters a context manager and exits it on tearDown.
mock(*args, **kw)
Enters
unittest.mock.patch
with the given arguments.This is syntactic sugur for:
context_manager(mock.patch(*args, **kw))
Here’s an example:
>>> class MyTests(zope.testing.setupstack.TestCase):
...
... def setUp(self):
... self.setUpDirectory()
... # Create a new directory in the one set up above, which gets
... # deleted in tear down:
... os.mkdir('example')
... self.context_manager(manager)
... self.mock("time.time", return_value=42)
...
... @self.register
... def _():
... print('done w test')
...
... def test(self):
... if here == os.getcwd():
... print('Failed to change directory')