Stack-based test doctest setUp and tearDown
============================================

Writing doctest setUp and tearDown functions can be a bit tedious,
especially when setUp/tearDown functions are combined.

the zope.testing.setupstack module provides a small framework for
automating test tear down.  It provides a generic setUp function that
sets up a stack. Normal test setUp functions call this function to set
up the stack and then use the register function to register tear-down
functions. 

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)

We don't have to call zope.testing.setupstack.setUp, because
setUpDirectory calls it for us.

Now the current working directory has changed:

    >>> here == os.getcwd()
    False

We can create files to out heart's content:

    >>> open('Data.fs', 'w').write('xxx')
    >>> os.path.exists('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 hasattr(os, 'symlink'):
    ...     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('Data.fs')
    False
