plone.testing 4.0a5

Introduction
============

.. contents:: Table of contents

``plone.testing`` provides tools for writing unit and integration tests in a
Zope and Plone environment. It is not tied to Plone, and it does not depend on
Zope 2 (although it has some optional Zope 2-only features).

``plone.testing`` builds on `zope.testing`_, in particular its layers concept.
This package also aims to promote some "good practice" for writing tests of
various types.

**Note:** If you are working with Plone, there is a complementary package
`plone.app.testing`_, which builds on ``plone.testing`` to provide
additional layers useful for testing Plone add-ons.

If you are new to automated testing and test driven development, you should
spend some time learning about those concepts. Some useful references include:

* `The Wikipedia article on unit testing <http://en.wikipedia.org/wiki/Unit_testing>`_
* `The Dive Into Python chapter on testing <http://diveintopython.org/unit_testing/index.html>`_

Bear in mind that different Python frameworks have slightly different takes on
how to approach testing. Therefore, you may find examples that are different
to those shown below. The core concepts should be consistent, however.

Compatibility
-------------

``plone.testing`` 4.x has only been tested with Python 2.6. If you're using the
optional Zope 2 layers, you must use Zope version 2.12 or later.
Look at ``plone.testing`` 3.x for Zope 2.10 support.

Definitions
-----------

In this documentation, we will use a number of testing-related terms. The
following definitions apply:

Unit test
An automated test (i.e. one written in code) that tests a single unit
(normally a function) in isolation. A unit test attempts to prove that the
given function works as expected and gives the correct output given a
particular input. It is common to have a number of unit tests for a single
function, testing different inputs, including boundary cases and errors.
Unit tests are typically quick to write and run.
Integration test
An automated test that tests how a number of units interact. In a Zope
context, this often pertains to how a particular object or view interacts
with the Zope framework, the ZODB persistence engine, and so on.
Integration tests usually require some setup and can be slower to run than
unit tests. It is common to have fewer integration tests than unit test.
Functional test
An automated test that tests a feature in an "end-to-end" fashion. In a
Zope context, that normally means that it invokes an action in the same
way that a user would, i.e. through a web request. Functional tests are
normally slower to run than either unit or integration tests, and can be
significantly slower to run. It is therefore common to have only a few
functional tests for each major feature, relying on unit and integration
tests for the bulk of testing.
Black box testing
Testing which only considers the system's defined inputs and outputs. For
example, a functional test is normally a black box test that provides
inputs only through the defined interface (e.g. URLs published in a web
application), and makes assertions only on end outputs (e.g. the response
returned for requests to those URLs).
White box testing
Testing which examines the internal state of a system to make assertions.
Authors of unit and integration tests normally have significant knowledge
of the implementation of the code under test, and can examine such things
as data in a database or changes to the system's environment to determine
if the test succeeded or failed.
Assertion
A check that determines whether a test succeeds or fails. For example, if
a unit test for the function ``foo()`` expects it to return the value 1,
an assertion could be written to verify this fact. A test is said to
*fail* if any of its assertions fail. A test always contains one or more
assertions.
Test case
A single unit, integration or functional test. Often shortened to just
*test*. A test case sets up, executes and makes assertions against a
single scenario that bears testing.
Test fixture
The state used as a baseline for one or more tests. The test fixture is
*set up* before each test is executed, and *torn down* afterwards. This is
a pre-requisite for *test isolation* - the principle that tests should be
independent of one another.
Layer
The configuration of a test fixture shared by a number of tests. All test
cases that belong to a particular layer will be executed together. The
layer is *set up* once before the tests are executed, and *torn down* once
after. Layers may depend on one another. Any *base layers* are set up
before and torn down after a particular *child layer* is used. The test
runner will order test execution to minimise layer setup and tear-down.
Test suite
A collection of test cases (and layers) that are executed together.
Test runner
The program which executes tests. This is responsible for calling layer
and test fixture set-up and tear-down methods. It also reports on the test
run, usually by printing output to the console.
Coverage
To have confidence in your code, you should ensure it is adequately
covered by tests. That is, each line of code, and each possible branching
point (loops, ``if`` statements) should be executed by a test. This is
known as *coverage*, and is normally measured as a percentage of lines of
non-test code covered by tests. Coverage can be measured by the test
runner, which keeps track of which lines of code were executed in a given
test run.
Doctest
A style of testing where tests are written as examples that could be typed
into the interactive Python interpreter. The test runner executes each
example and checks the actual output against the expected output. Doctests
can either be placed in the docstring of a method, or in a separate file.
The use of doctests is largely a personal preference. Some developers like
to write documentation as doctests, which has the advantage that code
samples can be automatically tested for correctness. You can read more
about doctests on `Wikipedia <http://en.wikipedia.org/wiki/Doctest>`_.

Installation and usage
======================

To use ``plone.testing`` in your own package, you need to add it as a
dependency. Most people prefer to keep test-only dependencies separate, so
that they do not need to be installed in scenarios (such as on a production
server) where the tests will not be run. This can be achieved using a
``test`` extra.

In ``setup.py``, add or modify the ``extras_require`` option, like so::

extras_require = {
'test': [
'plone.testing',
]
},

You can add other test-only dependencies to that list as well, of course.

To run tests, you need a test runner. If you are using ``zc.buildout``, you
can install a test runner using the `zc.recipe.testrunner`_ recipe. For
example, you could add the following to your ``buildout.cfg``::

[test]
recipe = zc.recipe.testrunner
eggs =
my.package [test]
defaults = ['--auto-color', '--auto-progress']

You'll also need to add this part to the ``parts`` list, of course::

[buildout]
parts =
...
test

In this example, have listed a single package to test, called ``my.package``,
and asked for it to be installed with the ``[test]`` extra. This will install
any regular dependencies (listed in the ``install_requires`` option in
``setup.py``), as well as those in the list associated with the ``test`` key
in the ``extras_require`` option.

Note that it becomes important to properly list your dependencies here,
because the test runner will only be aware of the packages explicitly listed,
and their dependencies. For example, if your package depends on Zope 2, you
need to list ``Zope2`` in the ``install_requires`` list in ``setup.py``; ditto
for ``Plone``, or indeed any other package you import from.

Once you have re-run buildout, the test runner will be installed as
``bin/test`` (the executable name is taken from the name of the buildout
part). You can execute it without arguments to run all tests of each egg
listed in the ``eggs`` list::

$ bin/test

If you have listed several eggs, and you want to run the tests for a
particular one, you can do::

$ bin/test -s my.package

If you want to run only a particular test within this package, use the ``-t``
option. This can be passed a regular expression matching either a doctest file
name or a test method name.

$ bin/test -s my.package -t test_spaceship

There are other command line options, which you can find by running::

$ bin/test --help

Also note the ``defaults`` option in the buildout configuration. This can be
used to set default command line options. Some commonly useful options are
shown above.

Coverage reporting
------------------

When writing tests, it is useful to know how well your tests cover your code.
You can create coverage reports via the excellent `coverage`_ library. In
order to use it, we need to install it and a reporting script::

[buildout]
parts =
...
test
coverage
report

[coverage]
recipe = zc.recipe.egg
eggs = coverage
initialization =
include = '--source=${buildout:directory}/src'
sys.argv = sys.argv[:] + ['run', include, 'bin/test', '--all']

[report]
recipe = zc.recipe.egg
eggs = coverage
scripts = coverage=report
initialization =
sys.argv = sys.argv[:] + ['html', '-i']

This will run the ``bin/test`` script with arguments like `--all` to run all
layers. You can also specify no or some other arguments. It will place coverage
reporting information in a ``.coverage`` file inside your buildout root.
Via the ``--source`` argument you specify the directories containing code you
want to cover. The coverage script would otherwise generate coverage
information for all executed code, including other packages and even the
standard library.

Running the ``bin/report`` script will generate a human readable HTML
representation of the run in the `htmlcov` directory. Open the contained
`index.html` in a browser to see the result.

If you want to generate an XML representation suitable for the `Cobertura`_
plugin of `Hudson`_, you can add another part::

[buildout]
parts =
...
report-xml

[report-xml]
recipe = zc.recipe.egg
eggs = coverage
scripts = coverage=report-xml
initialization =
sys.argv = sys.argv[:] + ['xml', '-i']

This will generate a ``coverage.xml`` file in the buildout root.

Optional dependencies
---------------------

``plone.testing`` comes with a core set of tools for managing layers, which
depends only on `zope.testing`_ and `unittest2`_. In addition, there are
several layers and helper functions which can be used in your own tests (or
as bases for your own layers). Some of these have deeper dependencies.
However, these dependencies are optional and not installed by default. If you
don't use the relevant layers, you can safely ignore them.

``plone.testing`` does specify these dependencies, however, using the
``setuptools`` "extras" feature. You can depend on one or more extras in
your own ``setup.py`` ``install_requires`` or ``extras_require`` option
using the same square bracket notation shown for the ``[test]`` buildout part
above. For example, if you need both the ``zca`` and ``publisher`` extras, you
can have the following in your ``setup.py``::

extras_require = {
'test': [
'plone.testing [zca, publisher]',
]
},

The available extras are:

``zodb``
ZODB testing. Depends on ``ZODB3``. The relevant layers and helpers are in
the module ``plone.testing.zodb``.
``zca``
Zope Component Architecture testing. Depends on core Zope Component
Architecture packages such as ``zope.component`` and ``zope.event``. The
relevant layers and helpers are in the module ``plone.testing.zca``.
``security``
Security testing. Depends on ``zope.security``. The relevant layers and
helpers are in the module ``plone.testing.security``.
``publisher``
Zope Publisher testing. Depends on ``zope.app.publisher`` and sets up
ZCML directives. The relevant layers and helpers are in the module
``plone.testing.publisher``.
``z2``
Zope 2 testing. Depends on the ``Zope2`` egg, which includes all the
dependencies of the Zope 2 application server. The relevant layers and
helpers are in the module ``plone.testing.z2``

Adding a test buildout to your package
--------------------------------------

When creating re-usable, mostly stand-alone packages, it is often useful to be
able to include a buildout with the package sources itself that can be used to
create a test runner. This is a popular approach for many Zope packages, for
example. In fact, ``plone.testing`` itself uses this kind of layout.

To have a self-contained buildout in your package, the following is required:

* You need a ``buildout.cfg`` at the root of the package.
* In most cases, you always want a ``bootstrap.py`` file to make it easier for
people to set up a fresh buildout.
* Your package sources need to be inside a ``src`` directory. If you're using
namespace packages, that means the top level package should be in the
``src`` directory.
* The ``src`` directory must be referenced in ``setup.py``.

For example, ``plone.testing`` has the following layout::

plone.testing/
plone.testing/setup.py
plone.testing/bootstrap.py
plone.testing/buildout.cfg
plone.testing/README.txt
plone.testing/src/
plone.testing/src/plone
plone.testing/src/plone/__init__.py
plone.testing/src/plone/testing/
plone.testing/src/plone/testing/*

In ``setup.py``, the following arguments are required::

packages=find_packages('src'),
package_dir={'': 'src'},

This tells ``setuptools`` where to find the source code.

The ``buildout.cfg`` for ``plone.testing`` looks like this::

[buildout]
extends =
http://download.zope.org/Zope2/index/2.12.12/versions.cfg
parts = coverage test report report-xml
develop = .

[test]
recipe = collective.xmltestreport
eggs =
plone.testing [test]
defaults = ['--auto-color', '--auto-progress']

[coverage]
recipe = zc.recipe.egg
eggs = coverage
initialization =
include = '--source=${buildout:directory}/src'
sys.argv = sys.argv[:] + ['run', include, 'bin/test', '--all', '--xml']

[report]
recipe = zc.recipe.egg
eggs = coverage
scripts = coverage=report
initialization =
sys.argv = sys.argv[:] + ['html', '-i']

[report-xml]
recipe = zc.recipe.egg
eggs = coverage
scripts = coverage=report-xml
initialization =
sys.argv = sys.argv[:] + ['xml', '-i']

Obviously, you should adjust the package name in the ``eggs`` list and the
version set in the ``extends`` line as appropriate.

You can of course also add additional buildout parts, for example to include
some development/debugging tools, or even a running application server for
testing purposes.

*Hint:* If you use this package layout, you should avoid checking any
files or directories generated by buildout into your version control
repository. You want to ignore:

* ``.coverage``
* ``.installed.cfg``
* ``bin``
* ``coverage.xml``
* ``develop-eggs``
* ``htmlcov``
* ``parts``
* ``src/*.egg-info``

Layers
======

In large part, ``plone.testing`` is about layers. It provides:

* A set of layers (outlined below), which you can use or extend.
* A set of tools for working with layers
* A mini-framework to make it easy to write layers and manage shared resources
associated with layers.

We'll discuss the last two items here, before showing how to write tests that
use layers.

Layer basics
------------

Layers are used to create test fixtures that are shared by multiple test
cases. For example, if you are writing a set of integration tests, you may
need to set up a database and configure various components to access that
database. This type of test fixture setup can be resource-intensive and
time-consuming. If it is possible to only perform the setup and tear-down once
for a set of tests without losing isolation between those tests, test runs can
often be sped up significantly.

Layers also allow re-use of test fixtures and set-up/tear-down code.
``plone.testing`` provides a number of useful (but optional) layers that
manage test fixtures for common Zope testing scenarios, letting you focus on
the actual test authoring.

At the most basic, a layer is an object with the following methods and
attributes:

``setUp()``
Called by the test runner when the layer is to be set up. This is called
exactly once for each layer used during a test run.
``tearDown()``
Called by the test runner when the layer is to be torn down. As with
``setUp()``, this is called exactly once for each layer.
``testSetUp()``
Called immediately before each test case that uses the layer is executed.
This is useful for setting up aspects of the fixture that are managed on
a per-test basis, as opposed to fixture shared among all tests.
``testTearDown()``
Called immediately after each test case that uses the layer is executed.
This is a chance to perform any post-test cleanup to ensure the fixture
is ready for the next test.
``__bases__``
A tuple of base layers.

Each test case is associated with zero or one layer. (The syntax for
specifying the layer is shown in the section "Writing tests" below.) All the
tests associated with a given layer will be executed together.

Layers can depend on one another (as indicated in the ``__bases__`` tuple),
allowing one layer to build on the fixture created by another. Base layers are
set up before and torn down after their dependants.

For example, if the test runner is executing some tests that belong to layer
A, and some other tests that belong to layer B, both of which depend on layer
C, the order of execution might be::

1. C.setUp()
1.1. A.setUp()

1.1.1. C.testSetUp()
1.1.2. A.testSetUp()
1.1.3. [One test using layer A]
1.1.4. A.testTearDown()
1.1.5. C.testTearDown()

1.1.6. C.testSetUp()
1.1.7. A.testSetUp()
1.1.8. [Another test using layer A]
1.1.9. A.testTearDown()
1.1.10. C.testTearDown()

1.2. A.tearDown()
1.3. B.setUp()

1.3.1. C.testSetUp()
1.3.2. B.testSetUp()
1.3.3. [One test using layer B]
1.3.4. B.testTearDown()
1.3.5. C.testTearDown()

1.3.6. C.testSetUp()
1.3.7. B.testSetUp()
1.3.8. [Another test using layer B]
1.3.9. B.testTearDown()
1.3.10. C.testTearDown()

1.4. B.tearDown()
2. C.tearDown()

A base layer may of course depend on other base layers. In the case of nested
dependencies like this, the order of set up and tear-down as calculated by the
test runner is similar to the way in which Python searches for the method to
invoke in the case of multiple inheritance.

Writing layers
--------------

The easiest way to create a new layer is to use the ``Layer`` base class and
implement the ``setUp()``, ``tearDown()``, ``testSetUp()`` and
``testTearDown()`` methods as needed. All four are optional. The default
implementation of each does nothing.

By convention, layers are created in a module called ``testing.py`` at the top
level of your package. The idea is that other packages that extend your
package can re-use your layers for their own testing.

A simple layer may look like this:

>>> from plone.testing import Layer
>>> class SpaceShip(Layer):
...
... def setUp(self):
... print "Assembling space ship"
...
... def tearDown(self):
... print "Disasembling space ship"
...
... def testSetUp(self):
... print "Fuelling space ship in preparation for test"
...
... def testTearDown(self):
... print "Emptying the fuel tank"

Before this layer can be used, it must be instantiated. Layers are normally
instantiated exactly once, since by nature they are shared between tests. This
becomes important when you start to manage resources (such as persistent data,
database connections, or other shared resources) in layers.

The layer instance is conventionally also found in ``testing.py``, just after
the layer class definition.

>>> SPACE_SHIP = SpaceShip()

**Note:** Since the layer is instantiated in module scope, it will be
created as soon as the ``testing`` module is imported. It is therefore
very important that the layer class is inexpensive and safe to create. In
general, you should avoid doing anything non-trivial in the ``__init__()``
method of your layer class. All setup should happen in the ``setUp()``
method. If you *do* implement ``__init__()``, be sure to call the ``super``
version as well.

The layer shown above did not have any base layers (dependencies). Here is an
example of another layer that depends on it:

>>> class ZIGSpaceShip(Layer):
... defaultBases = (SPACE_SHIP,)
...
... def setUp(self):
... print "Installing main canon"

>>> ZIG = ZIGSpaceShip()

Here, we have explicitly listed the base layers on which ``ZIGSpaceShip``
depends, in the ``defaultBases`` attribute. This is used by the ``Layer``
base class to set the layer bases in a way that can also be overridden: see
below.

Note that we use the layer *instance* in the ``defaultBases`` tuple, not the
class. Layer dependencies always pertain to specific layer instances. Above,
we are really saying that *instances* of ``ZIGSpaceShip`` will, by default,
require the ``SPACE_SHIP`` layer to be set up first.

**Note:** You may find it useful to create other layer base/mix-in classes
that extend ``plone.testing.Layer`` and provide helper methods for use in
your own layers. This is perfectly acceptable, but please do not confuse a
layer base class used in this manner with the concept of a *base layer* as
described above:

* A class deriving from ``plone.testing.Layer`` is known as a *layer
class*. It defines the behaviour of the layer by implementing the
lifecycle methods ``setUp()``, ``tearDown()``, ``testSetUp()`` and/or
``testTearDown()``.
* A layer class can be instantiated into an actual layer. When a layer is
associated with a test, it is the layer *instance* that is used.
* The instance is usually a shared, module-global object, although in
some cases it is useful to create copies of layers by instantiating the
class more than once.
* Subclassing an existing layer class is just straightforward OOP re-use:
the test runner is not aware of the subclassing relationship.
* A layer *instance* can be associated with any number of layer *bases*,
via its ``__bases__`` property (which is usually via the
``defaultBases`` variable in the class body and/or overridden using the
``bases`` argument to the ``Layer`` constructor). These bases are layer
*instances*, not classes. The test runner will inspect the ``__bases__``
attribute of each layer instance it sets up to calculate layer
pre-requisites and dependencies.

Also note that the `zope.testing`_ documentation contains examples of
layers that are "old-style" classes where the ``setUp()`` and
``tearDown()`` methods are ``classmethod`` methods and class inheritance
syntax is used to specify base layers. Whilst this pattern works, we
discourage its use, because the classes created using this pattern are not
really used as classes. The concept of layer bases is slightly different
from class inheritance, and using the ``class`` keyword to create layers
with base layers leads to a number of "gotchas" that are best avoided.

Advanced - overriding bases
---------------------------

In some cases, it may be useful to create a copy of a layer, but change its
bases. One reason to do this may if you are re-using a layer from another
module, and you need to change the order in which layers are set up and torn
down.

Normally, of course, you would just re-use the layer instance, either directly
in a test, or in the ``defaultBases`` tuple of another layer, but if you need
to change the bases, you can pass a new list of bases to the layer instance
constructor:

>>> class CATSMessage(Layer):
...
... def setUp(self):
... print "All your base are belong to us"
...
... def tearDown(self):
... print "For great justice"

>>> CATS_MESSAGE = CATSMessage()

>>> ZERO_WING = ZIGSpaceShip(bases=(SPACE_SHIP, CATS_MESSAGE,), name="ZIGSpaceShip:CATSMessage")

Please note that when overriding bases like this, the ``name`` argument is
required. This is because each layer (using in a given test run) must have
a unique name. The default is to use the layer class name, but this obviously
only works for one instantiation. Therefore, ``plone.testing`` requires a
name when setting ``bases`` explicitly.

Please take great care when changing layer bases like this. The layer
implementation may make assumptions about the test fixture that was set up
by its bases. If you change the order in which the bases are listed, or remove
a base altogether, the layer may fail to set up correctly.

Also, bear in mind that the new layer instance is independent of the original
layer instance, so any resources defined in the layer are likely to be
duplicated.

Layer combinations
------------------

Sometimes, it is useful to be able to combine several layers into one, without
adding any new fixture. One way to do this is to use the ``Layer`` class
directly and instantiate it with new bases:

>>> COMBI_LAYER = Layer(bases=(CATS_MESSAGE, SPACE_SHIP,), name="Combi")

Here, we have created a "no-op" layer with two bases: ``CATS_MESSAGE`` and
``SPACE_SHIP``, named ``Combi``.

Please note that when using ``Layer`` directly like this, the ``name``
argument is required. This is to allow the test runner to identify the layer
correctly. Normally, the class name of the layer is used as a basis for the
name, but when using the ``Layer`` base class directly, this is unlikely to be
unique or descriptive.

Layer resources
---------------

Many layers will manage one or more resources that are used either by other
layers, or by tests themselves. Examples may include database connections,
thread-local objects, or configuration data.

``plone.testing`` contains a simple resource storage abstraction that makes it
easy to access resources from dependant layers or tests. The resource storage
uses dictionary notation:

>>> class WarpDrive(object):
... """A shared resource"""
...
... def __init__(self, maxSpeed):
... self.maxSpeed = maxSpeed
... self.running = False
...
... def start(self, speed):
... if speed > self.maxSpeed:
... print "We need more power!"
... else:
... print "Going to warp at speed", speed
... self.running = True
...
... def stop(self):
... self.running = False

>>> class ConstitutionClassSpaceShip(Layer):
... defaultBases = (SPACE_SHIP,)
...
... def setUp(self):
... self['warpDrive'] = WarpDrive(8.0)
...
... def tearDown(self):
... del self['warpDrive']

>>> CONSTITUTION_CLASS_SPACE_SHIP = ConstitutionClassSpaceShip()

>>> class GalaxyClassSpaceShip(Layer):
... defaultBases = (CONSTITUTION_CLASS_SPACE_SHIP,)
...
... def setUp(self):
... # Upgrade the warp drive
... self.previousMaxSpeed = self['warpDrive'].maxSpeed
... self['warpDrive'].maxSpeed = 9.5
...
... def tearDown(self):
... # Restore warp drive to its previous speed
... self['warpDrive'].maxSpeed = self.previousMaxSpeed

>>> GALAXY_CLASS_SPACE_SHIP = GalaxyClassSpaceShip()

As shown, layers (that derive from ``plone.testing.Layer``) support item
(dict-like) assignment, access and deletion of arbitrary resources under
string keys.

**Important:** If a layer creates a resource (by assigning an object to
a key on ``self`` as shown above) during fixture setup-up, it must also
delete the resource on tear-down. Set-up and deletion should be symmetric:
if the resource is assigned during ``setUp()`` it should be deleted in
``tearDown()``; if it's created in ``testSetUp()`` it should be deleted
in ``testTearDown()``.

A resource defined in a base layer is accessible from and through a child
layer. If a resource is set on a child using a key that also exists in a base
layer, the child version will shadow the base version until the child layer is
torn down (presuming it deletes the resource, which it should), but the base
layer version remains intact.

**Note:** Accessing a resource is analogous to accessing an instance
variable. For example, if a base layer assigns a resource to a given key
in its ``setUp()`` method, a child layer shadows that resource with
another object under the same key, the shadowed resource will by used
during the ``testSetUp()`` and ``testTearDown()`` lifecycle methods if
implemented by the *base* layer as well. This will be the case until
the child layer "pops" the resource by deleting it, normally in its
``tearDown()``.

Conversely, if (as shown above) the child layer accesses and modifies the
object, it will modify the original.

**Note:** It is sometimes necessary (or desirable) to modify a shared
resource in a child layer, as shown in the example above. In this case,
however, it is very important to restore the original state when the layer
is torn down. Otherwise, other layers or tests using the base layer
directly may be affected in difficult-to-debug ways.

If the same key is used in multiple base layers, the rules for choosing which
version to use are similar to those that apply when choosing an attribute or
method to use in the case of multiple inheritance.

In the example above, we used the resource manager for the ``warpDrive``
object, but we assigned the ``previousMaxSpeed`` variable to ``self``. This is
because ``previousMaxSpeed`` is internal to the layer and should not be shared
with any other layers that happen to use this layer as a base. Nor should it
be used by any test cases. Conversely, ``warpDrive`` is a shared resource that
is exposed to other layers and test cases.

The distinction becomes even more important when you consider how a test case
may access the shared resource. We'll discuss how to write test cases that use
layers shortly, but consider the following test:

>>> import unittest2 as unittest
>>> class TestFasterThanLightTravel(unittest.TestCase):
... layer = GALAXY_CLASS_SPACE_SHIP
...
... def test_hyperdrive(self):
... warpDrive = self.layer['warpDrive']
... warpDrive.start(8)

This test needs access to the shared resource. It knows that its layer defines
one called ``warpDrive``. It does not know or care that the warp drive was
actually initiated by the ``ConstitutionClassSpaceShip`` base layer.

If, however, the base layer had assigned the resource as an instance variable,
it would not inherit to child layers (remember: layer bases are not base
classes!). The syntax to access it would be::

self.layer.__bases__[0].warpDrive

which is not only ugly, but brittle: if the list of bases is changed, the
expression above may lead to an attribute error.

Writing tests
=============

Tests are usually written in one of two ways: As methods on a class that
derives from ``unittest.TestCase`` (this is sometimes known as "Python tests"
or "JUnit-style tests"), or using doctest syntax.

You should realise that although the relevant frameworks (``unittest``,
``unittest2`` and ``doctest``) often talk about unit testing, these tools are
also used to write integration and functional tests. The distinction between
unit, integration and functional tests is largely practical: you use the same
techniques to set up a fixture or write assertions for an integration test as
you would for a unit test. The difference lies in what that fixture contains,
and how you invoke the code under test. In general, a true unit test will have
a minimal or no test fixture, whereas an integration test will have a fixture
that contains the components your code is integrating with. A functional test
will have a fixture that contains enough of the full system to execute and
test an "end-to-end" scenario.

Python tests
------------

Python tests use the Python `unittest`_ module, or its cousin `unittest2`_
(see below). They should be placed in a module or package called ``tests``
for the test runner to pick them up.

For small packages, a single module called ``tests.py`` will normally contain
all tests. For larger packages, it is common to have a ``tests`` package that
contains a number of modules with tests. These need to start with the word
``test``, e.g. ``tests/test_foo.py`` or ``tests/test_bar.py``. Don't forget
the ``__init__.py`` in the ``tests`` package, too!

unittest2
~~~~~~~~~

In Python 2.7+, the ``unittest`` module has grown several new and useful
features. To make use of these in Python 2.4, 2.5 and 2.6, an add-on module
called `unittest2`_ can be installed. ``plone.testing`` depends on
``unittest2`` (and uses it for its own tests), so you will have access to it
if you depend on ``plone.testing``.

We will use ``unittest2`` for the examples in this document, but import it
with an alias of ``unittest``. This makes the code forward compatible with
Python 2.7, where the built-in ``unittest`` module will have all the features
of the ``unittest2`` module.

Please note that the `zope.testing`_ test runner at the time of writing
(version 3.9.3) does not (yet) support the new ``setUpClass()``,
``tearDownClass()``, ``setUpModule()`` and ``tearDownModule()`` hooks from
``unittest2``. This is not normally a problem, since we tend to use layers to
manage complex fixtures, but it is important to be aware of nonetheless.

Test modules, classes and functions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Python tests are written with classes that derive from the base class
``TestCase``. Each test is written as a method that takes no arguments and
has a name starting with ``test``. Other methods can be added and called from
test methods as appropriate, e.g. to share some test logic.

Two special methods, ``setUp()`` and ``tearDown()``, can also be added. These
will be called before or after each test, respectively, and provide a useful
place to construct and clean up test fixtures without writing a custom layer.
They are obviously not as re-usable as layers, though.

*Hint:* Somewhat confusingly, the ``setUp()`` and ``tearDown()`` methods in
a test case class are the equivalent of the ``testSetUp()`` and
``testTearDown()`` methods of a layer class.

A layer can be specified by setting the ``layer`` class attribute to a layer
instance. If layers are used in conjunction with ``setUp()`` and
``tearDown()`` methods in the test class itself, the class' ``setUp()`` method
will be called after the layer's ``testSetUp()`` method, and the class'
``tearDown()`` method will be called before the layer's ``testTearDown()``
method.

The ``TestCase`` base class contains a number of methods which can be used to
write assertions. They all take the form ``self.assertSomething()``, e.g.
``self.assertEqual(result, expectedValue)``. See the `unittest`_ and/or
`unittest2`_ documentation for details.

Putting this together, let's expand on our previous example unit test:

>>> import unittest2 as unittest

>>> class TestFasterThanLightTravel(unittest.TestCase):
... layer = GALAXY_CLASS_SPACE_SHIP
...
... def setUp(self):
... self.warpDrive = self.layer['warpDrive']
... self.warpDrive.stop()
...
... def tearDown(self):
... self.warpDrive.stop()
...
... def test_warp8(self):
... self.warpDrive.start(8)
... self.assertEqual(self.warpDrive.running, True)
...
... def test_max_speed(self):
... tooFast = self.warpDrive.maxSpeed + 0.1
... self.warpDrive.start(tooFast)
... self.assertEqual(self.warpDrive.running, False)

A few things to note:

* The class derives from ``unittest.TestCase``.
* The ``layer`` class attribute is set to a layer instance (not a layer
class!) defined previously. This would typically be imported from a
``testing`` module.
* There are two tests here: ``test_warp8()`` and ``test_max_speed()``.
* We have used the ``self.assertEqual()`` assertion in both tests to check the
result of executing the ``start()`` method on the warp drive.
* We have used the ``setUp()`` method to fetch the ``warpDrive`` resource and
ensure that it is stopped before each test is executed. Assigning a variable
to ``self`` is a useful way to provide some state to each test method,
though be careful about data leaking between tests: in general, you cannot
predict the order in which tests will run, and tests should always be
independent.
* We have used the ``tearDown()`` method to make sure the warp
drive is really stopped after each test.

Test suites
~~~~~~~~~~~

If you are using version 3.8.0 or later of `zope.testing`_, a class like the
one above is all you need: any class deriving from ``TestCase`` in a module
with a name starting with ``test`` will be examined for test methods. Those
tests are then collected into a test suite and executed.

With older versions of `zope.testing`_, you need to add a ``test_suite()``
function in each module that returns the tests in the test suite. The
`unittest`_ module contains several tools to construct suites, but one of the
simplest is to use the default test loader to load all tests in the current
module:

>>> def test_suite():
... return unittest.defaultTestLoader.loadTestsFromName(__name__)

If you need to load tests explicitly, you can use the ``TestSuite`` API from
the `unittest`_ module. For example:

>>> def test_suite():
... suite = unittest.TestSuite()
... suite.addTests([
... unittest.makeSuite(TestFasterThanLightTravel)
... ])
... return suite

The ``makeSuite()`` function creates a test suite from the test methods in
the given class (which must derive from ``TestCase``). This suite is then
appended to an overall suite, which is returned from the ``test_suite()``
method. Note that ``addTests()`` takes a list of suites (which are coalesced
into a single suite). We'll add additional suites later.

See the `unittest`_ documentation for other options.

**Note:** Adding a ``test_suite()`` method to a module disables automatic
test discovery, even when using a recent version of ``zope.testing``.

Doctests
--------

Doctests can be written in two ways: as the contents of a docstring (usually,
but not always, as a means of illustrating and testing the functionality of
the method or class where the docstring appears), or as a separate text file.
In both cases, the standard `doctest`_ module is used. See its documentation
for details about doctest syntax and conventions.

Doctests are used in two different ways:

* To test documentation. That is, to ensure that code examples contained in
documentation are valid and continue to work as the software is updated.
* As a convenient syntax for writing tests.

These two approaches use the same testing APIs and techniques. The difference
is mostly about mindset. However, it is important to avoid falling into the
trap that tests can substitute for good documentation or vice-a-versa. Tests
usually need to systematically go through inputs and outputs and cover off a
number of corner cases. Documentation should tell a compelling narrative and
usually focus on the main usage scenarios. Trying to kill these two birds with
one stone normally leaves you with an unappealing pile of stones and feathers.

Docstring doctests
~~~~~~~~~~~~~~~~~~

Doctests can be added to any module, class or function docstring::

def canOutrunKlingons(warpDrive):
"""Find out of the given warp drive can outrun Klingons.

Klingons travel at warp 8

>>> drive = WarpDrive(5)
>>> canOutrunKlingons(drive)
False

We have to be faster than that to outrun them.

>>> drive = WarpDrive(8.1)
>>> canOutrunKlingons(drive)
True

We can't outrun them if we're travelling exactly the same speed

>>> drive = WarpDrive(8.0)
>>> canOutrunKlingons(drive)
False

"""
return warpDrive.maxSpeed > 8.0

To add the doctests from a particular module to a test suite, you need to
use the ``test_suite()`` function hook:

>>> import doctest
>>> def test_suite():
... suite = unittest.TestSuite()
... suite.addTests([
... unittest.makeSuite(TestFasterThanLightTravel), # our previous test
... doctest.DocTestSuite('spaceship.utils'),
... ])
... return suite

Here, we have given the name of the module to check as a string dotted name.
It is also possible to import a module and pass it as an object. The code
above passes a list to ``addTests()``, making it easy to add several sets of
tests to the suite: the list can contain be constructed from calls to
``DocTestSuite()``, ``DocFileSuite()`` (shown below) and ``makeSuite()``
(shown above).

Remember that if you add a ``test_suite()`` function to a module that
also has ``TestCase``-derived python tests, those tests will no longer
be automatically picked up by ``zope.testing``, so you need to add them
to the test suite explicitly.

The example above illustrates a documentation-oriented doctest, where the
doctest forms part of the docstring of a public module. The same syntax can
be used for more systematic unit tests. For example, we could have a module
``spaceship.tests.test_spaceship`` with a set of methods like::

# It's often better to put the import into each method, but here we've
# imported the code under test at module level
from spaceship.utils import WarpDrive, canOutrunKlingons

def test_canOutrunKlingons_too_small():
"""Klingons travel at warp 8.0

>>> drive = WarpDrive(7.9)
>>> canOutrunKlingons(drive)
False

"""

def test_canOutrunKlingons_big():
"""Klingons travel at warp 8.0

>>> drive = WarpDrive(8.1)
>>> canOutrunKlingons(drive)
True

"""

def test_canOutrunKlingons_must_be_greater():
"""Klingons travel at warp 8.0

>>> drive = WarpDrive(8.0)
>>> canOutrunKlingons(drive)
False

"""

Here, we have created a number of small methods that have no body. They merely
serve as a container for docstrings with doctests. Since the module has no
globals, each test must import the code under test, which helps make import
errors more explicit.

File doctests
~~~~~~~~~~~~~

Doctests contained in a file are similar to those contained in docstrings.
File doctests are better suited to narrative documentation covering the usage
of an entire module or package.

For example, if we had a file called ``spaceship.txt`` with doctests, we could
add it to the test suite above with:

>>> def test_suite():
... suite = unittest.TestSuite()
... suite.addTests([
... unittest.makeSuite(TestFasterThanLightTravel),
... doctest.DocTestSuite('spaceship.utils'),
... doctest.DocFileSuite('spaceship.txt'),
... ])
... return suite

By default, the file is located relative to the module where the test
suite is defined. You can use ``../`` (even on Windows) to reference the
parent directory, which is sometimes useful if the doctest is inside a module
in a ``tests`` package.

**Note:** If you put the doctest ``test_suite()`` method in a module
inside a ``tests`` package, that module must have a name starting with
``test``. It is common to have ``tests/test_doctests.py`` that contains a
single ``test_suite()`` method that returns a suite of multiple doctests.

It is possible to pass several tests to the suite, e.g.::

>>> def test_suite():
... suite = unittest.TestSuite()
... suite.addTests([
... unittest.makeSuite(TestFasterThanLightTravel),
... doctest.DocTestSuite('spaceship.utils'),
... doctest.DocFileSuite('spaceship.txt', 'warpdrive.txt',),
... ])
... return suite

The test runner will report each file as a separate test, i.e. the
``DocFileSuite()`` above would add two tests to the overall suite. Conversely,
a ``DocTestSuite()`` using a module with more than one docstring containing
doctests will report one test for each eligible docstring.

Doctest fixtures and layers
~~~~~~~~~~~~~~~~~~~~~~~~~~~

A docstring doctest will by default have access to any global symbol available
in the module where the docstring is found (e.g. anything defined or imported
in the module). The global namespace can be overridden by passing a ``globs``
keyword argument to the ``DocTestSuite()`` constructor, or augmented by
passing an ``extraglobs`` argument. Both should be given dictionaries.

A file doctest has an empty globals namespace by default. Globals may be
provided via the ``globs`` argument to ``DocFileSuite()``.

To manage a simple test fixture for a doctest, you can define set-up and
tear-down functions and pass them as the ``setUp`` and ``tearDown``
arguments respectively. These are both passed a single argument, a ``DocTest``
object. The most useful attribute of this object is ``globs``, which is a
mutable dictionary of globals available in the test.

For example:

>>> def setUpKlingons(doctest):
... doctest.globs['oldStyleKlingons'] = True

>>> def tearDownKlingons(doctest):
... doctest.globs['oldStyleKlingons'] = False

>>> def test_suite():
... suite = unittest.TestSuite()
... suite.addTests([
... doctest.DocTestSuite('spaceship.utils', setUp=setUpKlingons, tearDown=tearDownKlingons),
... ])
... return suite

The same arguments are available on the ``DocFileSuite()`` constructor. The
set up method is called before each docstring in the given module for a
``DocTestSuite``, and before each file given in a ``DocFileSuite``.

Of course, we often want to use layers with doctests too. Unfortunately,
the ``unittest`` API is not aware of layers, so you can't just pass a layer
to the ``DocTestSuite()`` and ``DocFileSuite()`` constructors. Instead,
you have to set a ``layer`` attribute on the suite after it has been
constructed.

Furthermore, to use layer resources in a doctest, we need access to the layer
instance. The easiest way to do this is to pass it as a glob, conventionally
called 'layer'. This makes a global name 'layer' available in the doctest
itself, giving access to the test's layer instance.

To make it easier to do this, ``plone.testing`` comes with a helper function
called ``layered()``. Its first argument is a test suite. The second argument
is the layer.

For example:

>>> from plone.testing import layered
>>> def test_suite():
... suite = unittest.TestSuite()
... suite.addTests([
... layered(doctest.DocTestSuite('spaceship.utils'), layer=CONSTITUTION_CLASS_SPACE_SHIP),
... ])
... return suite

This is equivalent to:

>>> def test_suite():
... suite = unittest.TestSuite()
...
... spaceshipUtilTests = doctest.DocTestSuite('spaceship.utils', globs={'layer': CONSTITUTION_CLASS_SPACE_SHIP})
... spaceshipUtilTests.layer = CONSTITUTION_CLASS_SPACE_SHIP
... suite.addTest(spaceshipUtilTests)
...
... return suite

(In this example, we've opted to use ``addTest()`` to add a single suite,
instead of using ``addTests()`` to add multiple suites in one go.)

Zope testing tools
==================

Everything described so far in this document relies only on the standard
`unittest`_/`unittest2`_ and `doctest`_ modules and `zope.testing`_, and you
can use this package without any other dependencies.

However, there are also some tools (and layers) available in this package, as
well as in other packages, that are specifically useful for testing
applications that use various Zope-related frameworks.

Test cleanup
------------

If a test uses a global registry, it may be necessary to clean that registry
on set up and tear down of each test fixture. ``zope.testing`` provides a
mechanism to register cleanup handlers - methods that are called to clean
up global state. This can then be invoked in the ``setUp()`` and
`tearDown()`` fixture lifecycle methods of a test case.

>>> from zope.testing import cleanup

Let's say we had a global registry, implemented as a dictionary

>>> SOME_GLOBAL_REGISTRY = {}

If we wanted to clean this up on each test run, we could call ``clear()``
on the dict. Since that's a no-argument method, it is perfect as a cleanup
handler.

>>> cleanup.addCleanUp(SOME_GLOBAL_REGISTRY.clear)

We can now use the ``cleanUp()`` method to execute all registered
cleanups:

>>> cleanup.cleanUp()

This call could be placed in a ``setUp()`` and/or ``tearDown()`` method in a
test class, for example.

Event testing
-------------

You may wish to test some code that uses ``zope.event`` to fire specific
events. `zope.component`_ provides some helpers to capture and analyse
events.

>>> from zope.component import eventtesting

To use this, you first need to set up event testing. Some of the layers
shown below will do this for you, but you can do it yourself by calling
the ``eventtesting.setUp()`` method, e.g. from your own ``setUp()`` method:

>>> eventtesting.setUp()

This simply registers a few catch-all event handlers. Once you have
executed the code that is expected to fire events, you can use the
``getEvents()`` helper function to obtain a list of the event instances
caught:

>>> events = eventtesting.getEvents()

You can now examine ``events`` to see what events have been caught since the
last cleanup.

``getEvents()`` takes two optional arguments that can be used to filter the
returned list of events. The first (``event_type``) is an interface. If given,
only events providing this interface are returned. The second (``filter``) is
a callable taking one argument. If given, it will be called with each captured
event. Only those events where the filter function returns ``True`` will be
included.

The ``eventtesting`` module registers a cleanup action as outlined above. When
you call ``cleanup.cleanUp()`` (or ``eventtesting.clearEvents()``, which is
the handler it registers), the events list will be cleared, ready for the
next test. Here, we'll do it manually:

>>> eventtesting.clearEvents()

Mock requests
-------------

Many tests require a request object, often with particular request/form
variables set. `zope.publisher`_ contains a useful class for this purpose.

>>> from zope.publisher.browser import TestRequest

A simple test request can be constructed with no arguments:

>>> request = TestRequest()

To add a body input stream, pass a ``StringIO`` or file as the first
parameter. To set the environment (request headers), use the ``environ``
keyword argument. To simulate a submitted form, use the ``form`` keyword
argument:

>>> request = TestRequest(form=dict(field1='foo', field2=1))

Note that the ``form`` dict contains marshalled form fields, so modifiers like
``:int`` or ``:boolean`` should not be included in the field names, and
values should be converted to the appropriate type.

Registering components
----------------------

Many test fixtures will depend on having a minimum of Zope Component
Architecture (ZCA) components registered. In normal operation, these would
probably be registered via ZCML, but in a unit test, you should avoid loading
the full ZCML configuration of your package (and its dependencies).

Instead, you can use the Python API in `zope.component`_ to register
global components instantly. The three most commonly used functions are:

>>> from zope.component import provideAdapter
>>> from zope.component import provideUtility
>>> from zope.component import provideHandler

See the `zope.component`_ documentation for details about how to use these.

When registering global components like this, it is important to avoid test
leakage. The ``cleanup`` mechanism outlined above can be used to tear down the
component registry between each test. See also the
``plone.testing.zca.UNIT_TESTING`` layer, described below, which performs this
cleanup automatically via the ``testSetUp()``/``testTearDown()`` mechanism.

Alternatively, you can "stack" a new global component registry using the
``plone.testing.zca.pushGlobalRegistry()`` and
``plone.testing.zca.popGlobalRegistry()`` helpers. This makes it possible to
set up and tear down components that are specific to a given layer, and even
allow tests to safely call the global component API (or load ZCML - see below)
with proper tear-down. See the layer reference below for details.

Loading ZCML
------------

Integration tests often need to load ZCML configuration. This can be achieved
using the ``zope.configuration`` API.

>>> from zope.configuration import xmlconfig

The ``xmlconfig`` module contains two methods for loading ZCML.

``xmlconfig.string()`` can be used to load a literal string of ZCML:

>>> xmlconfig.string("""\
... <configure xmlns="http://namespaces.zope.org/zope" package="plone.testing">
... <include package="zope.component" file="meta.zcml" />
... </configure>
... """)
<zope.configuration.config.ConfigurationMachine object at ...>

Note that we need to set a package (used for relative imports and file
locations) explicitly here, using the ``package`` attribute of the
``<configure />`` element.

Also note that unless the optional second argument (``context``) is passed,
a new configuration machine will be created every time ``string()`` is called.
It therefore becomes necessary to explicitly ``<include />`` the files that
contain the directives you want to use (the one in ``zope.component`` is a
common example). Layers that set up ZCML configuration may expose a resource
which can be passed as the ``context`` parameter, usually called
``configurationContext`` - see below.

To load the configuration for a particular package, use ``xmlconfig.file()``:

>>> import zope.component
>>> context = xmlconfig.file('meta.zcml', zope.component)
>>> xmlconfig.file('configure.zcml', zope.component, context=context)
<zope.configuration.config.ConfigurationMachine object at ...>

This takes two required arguments: the file name and the module relative to
which it is to be found. Here, we have loaded two files: ``meta.zcml`` and
``configure.zcml``. The first call to ``xmlconfig.file()`` creates and
returns a configuration context. We re-use that for the subsequent invocation,
so that the directives configured are available.

Installing a Zope 2 product
---------------------------

Some packages (including all those in the ``Products.*`` namespace) have the
special status of being Zope 2 "products". These are recorded in a special
registry, and may have an ``initialize()`` hook in their top-level
``__init__.py`` that needs to be called for the package to be fully configured.

Zope 2 will find and execute any products during startup. For testing, we
need to explicitly list the products to install. Provided you are using
``plone.testing`` with Zope 2, you can use the following::

from plone.testing import z2

with z2.zopeApp() as app:
z2.installProduct(app, 'Products.ZCatalog')

This would normally be used during layer ``setUp()``. Note that the basic
Zope 2 application context must have been set up before doing this. The usual
way to ensure this, is to use a layer that is based on ``z2.STARTUP`` - see
below.

To tear down such a layer, you should do::

from plone.testing import z2

with z2.zopeApp() as app:
z2.uninstallProduct(app, 'Products.ZCatalog')

Note:

* Unlike the similarly-named function from ``ZopeTestCase``, these helpers
will work with any type of product. There is no distinction between a
"product" and a "package" (and no ``installPackage()``). However, you must
use the full name (``Products.*``) when registering a product.
* Installing a product in this manner is independent of ZCML configuration.
However, it is almost always necessary to install the package's ZCML
configuration first.

Functional testing
------------------

For functional tests that aim to simulate the browser, you can use
`zope.testbrowser`_ in a Python test or doctest::

>>> from zope.testbrowser.browser import Browser
>>> browser = Browser()

This provides a simple API to simulate browser input, without actually running
a web server thread or scripting a live browser (as tools such as Windmill
and Selenium do). The downside is that it is not possible to test JavaScript-
dependent behaviour.

If you are testing a Zope 2 application, you need to change the import
location slightly, and pass the application root to the method::

from plone.testing.z2 import Browser
browser = Browser(app)

You can get the application root from the ``app`` resource in any of the
Zope 2 layers in this package.

Beyond that, the `zope.testbrowser`_ documentation should cover how to use
the test browser.

**Hint:** The test browser will usually commit at the end of a request. To
avoid test fixture contamination, you should use a layer that fully
isolates each test, such as the ``z2.INTEGRATION_TESTING`` layer described
below.

Layer reference
===============

``plone.testing`` comes with several layers that are available to use directly
or extend. These are outlined below.

Zope Component Architecture
---------------------------

The Zope Component Architecture layers are found in the module
``plone.testing.zca``. If you depend on this, you can use the ``[zca]`` extra
when depending on ``plone.testing``.

Unit testing
~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.zca.UNIT_TESTING`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.zca.UnitTesting`` |
+------------+--------------------------------------------------+
| Bases: | None |
+------------+--------------------------------------------------+
| Resources: | None |
+------------+--------------------------------------------------+

This layer does not set up a fixture per se, but cleans up global state
before and after each test, using ``zope.testing.cleanup`` as described
above.

The net result is that each test has a clean global component registry. Thus,
it is safe to use the `zope.component`_ Python API (``provideAdapter()``,
``provideUtility()``, ``provideHandler()`` and so on) to register components.

Be careful with using this layer in combination with other layers. Because
it tears down the component registry between each test, it will clobber any
layer that sets up more permanent test fixture in the component registry.

Event testing
~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.zca.EVENT_TESTING`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.zca.EventTesting`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.zca.UNIT_TESTING`` |
+------------+--------------------------------------------------+
| Resources: | None |
+------------+--------------------------------------------------+

This layer extends the ``zca.UNIT_TESTING`` layer to enable the
``eventtesting`` support from ``zope.component``. Using this layer, you can
import and use ``zope.component.eventtesting.getEvent`` to inspect events
fired by the code under test.

See above for details.

Layer cleanup
~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.zca.LAYER_CLEANUP`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.zca.LayerCleanup`` |
+------------+--------------------------------------------------+
| Bases: | None |
+------------+--------------------------------------------------+
| Resources: | None |
+------------+--------------------------------------------------+

This layer calls the cleanup functions from ``zope.testing.cleanup`` on setup
and tear-down (but not between each test). It is useful as a base layer for
other layers that need as pristine an environment as possible.

Basic ZCML directives
~~~~~~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.zca.ZCML_DIRECTIVES`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.zca.ZCMLDirectives`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.zca.LAYER_CLEANUP`` |
+------------+--------------------------------------------------+
| Resources: | ``configurationContext`` |
+------------+--------------------------------------------------+

This registers a minimal set of ZCML directives, principally those found in
the ``zope.component`` package, and makes available a configuration context.
This allows custom ZCML to be loaded as described above.

The ``configurationContext`` resource should be used when loading custom ZCML.
To ensure isolation, you should stack this using the
``pushConfigurationContext()`` and ``popConfigurationContext()`` helpers.
For example, if you were writing a
``setUp()`` method in a layer that had ``zca.ZCML_DIRECTIVES`` as a base, you
could do::

self['configurationContext'] = context = zca.pushConfigurationContext(self.get('configurationContext'))
xmlconfig.string(someZCMLString, context=context)

This will create a new configuration context with the state of the base
layer's context. On tear-down, you should delete the layer-specific resource::

zca.popConfigurationContext()
del self['configurationContext']

*Note:* If you fail to do this, you may get problems if your layer is torn
down and then needs to be set up again later.

Mainly when later layers load ZCML files that have been already loaded by earlier layers,
the registration does not happen as the configuration context remembers it had
already loaded those files. Worse, it does not complain.

See above for more details about loading custom ZCML in a layer or test.

Helper functions
~~~~~~~~~~~~~~~~

The following helper functions are available in the ``plone.testing.zca``
module.

``setUpZcmlFiles(infos)``
Load a set of ZCML files and execute the corresponding registrations.

``infos`` parameter is a sequence of filename, package tuples
where filename is a string holding the ZCML file name
and package is a package instance ::

zca.setUpZcmlFiles([
("configure.zcml", plone.testing),
])

Before loading the files, it creates a new local configuration context
and a fresh copy of the global registry (by calling
``pushConfigurationContext()`` and ``pushGlobalRegistry()``).

**Warning**: If you call this function, you *must* reciprocally call
``tearDownZcmlFiles()`` as it tears down the new configuration context
and the new global registry.

``tearDownZcmlFiles()``
Pop the configuration context and the global registry, restoring the previous
context and registry.

It calls ``popConfigurationContext()`` and ``popGlobalRegistry()``.

Please heed the warning above: ``setUpZcmlFiles()`` and ``tearDownZcmlFiles()`` must be balanced.

``pushConfigurationContext(context=None)``
Create and return a copy of the passed-in ZCML configuration context, or a
brand new context if it is ``None``.

The purpose of this is to ensure that if a layer loads some ZCML files
(using the ``zope.configuration`` API during) its ``setUp()``, the state
of the configuration registry (which includes registered directives as
well as a list of already imported files, which will not be loaded again
even if explicitly included) can be torn down during ``tearDown()``.

The usual pattern is to keep the configuration context in a layer resource
called ``configurationContext``. In ``setUp()``, you would then use::

self['configurationContext'] = context = zca.pushConfigurationContext(self.get('configurationContext'))

# use 'context' to load some ZCML

In ``tearDown()``, you can then simply do::

zca.popConfigurationContext()
del self['configurationContext']

``pushGlobalRegistry(new=None)``
Create or obtain a stack of global component registries, and push a new
registry to the top of the stack. The net result is that
``zope.component.getGlobalSiteManager()`` and (an un-hooked)
``getSiteManager()`` will return the new registry instead of the default,
module-scope one. From this point onwards, calls to ``provideAdapter()``,
``provideUtility()`` and other functions that modify the global registry
will use the new registry.

If ``new`` is not given, a new registry is created that has the previous
global registry (site manager) as its sole base. This has the effect that
registrations in the previous default global registry are still available,
but new registrations are confined to the new registry.

**Warning**: If you call this function, you *must* reciprocally call
``popGlobalRegistry()``. That is, if you "push" a registry during layer
``setUp()``, you must "pop" it during ``tearDown()``. If you "push" during
``testSetUp()``, you must "pop" during ``testTearDown()``. If the calls
to push and pop are not balanced, you will leave your global registry in
a mess, which is not pretty.

Returns the new default global site manager. Also causes the site manager
hook from ``zope.site`` to be reset, clearing any local site managers as
appropriate.

``popGlobalRegistry()``
Pop the global site registry, restoring the previous registry to be the
default.

Please heed the warning above: push and pop must be balanced.

Returns the new default global site manager. Also causes the site manager
hook from ``zope.site`` to be reset, clearing any local site managers as
appropriate.

Zope Security
-------------

The Zope Security layers build can be found in the module
``plone.testing.security``.

If you depend on this, you can use the ``[security]`` extra when depending on
``plone.testing``.

Security checker isolation
~~~~~~~~~~~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.security.CHECKERS`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.security.Checkers`` |
+------------+--------------------------------------------------+
| Bases: | None |
+------------+--------------------------------------------------+
| Resources: | None |
+------------+--------------------------------------------------+

This layer ensures that security checkers used by ``zope.security`` are
isolated. Any checkers set up in a child layer will be removed cleanly during
tear-down.

Helper functions
~~~~~~~~~~~~~~~~

The security checker isolation outlined above is managed using two helper
functions found in the module ``plone.testing.security``:

``pushCheckers()``
Copy the current set of security checkers for later tear-down.
``popCheckers()``
Restore the set of security checkers to the state of the most recent
call to ``pushCheckers()``.

You *must* keep calls to ``pushCheckers()`` and ``popCheckers()`` in balance.
That usually means that if you call the former during layer setup, you should
call the latter during layer tear-down. Ditto for calls during test
setup/tear-down or within tests themselves.

Zope Publisher
--------------

The Zope Publisher layers build on the Zope Component Architecture layers.
They can be found in the module ``plone.testing.publisher``.

If you depend on this, you can use the ``[publisher]`` extra when depending on
``plone.testing``.

Publisher directives
~~~~~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.publisher.PUBLISHER_DIRECTIVES`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.publisher.PublisherDirectives`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.zca.ZCML_DIRECTIVES`` |
+------------+--------------------------------------------------+
| Resources: | None |
+------------+--------------------------------------------------+

This layer extends the ``zca.ZCML_DIRECTIVES`` layer to install additional
ZCML directives in the ``browser`` namespace (from
``zope.app.publisher.browser``) as well as those from ``zope.security``.
This allows browser views, browser pages and other UI components to be
registered, as well as the definition of new permissions.

As with ``zca.ZCML_DIRECTIVES``, you should use the ``configurationContext``
resource when loading ZCML strings or files, and the
``stackConfigurationRegistry()`` helper to create a layer-specific version
of this resource resource. See above.

ZODB
----

The ZODB layers set up a test fixture with a persistent ZODB. The ZODB
instance uses ``DemoStorage``, so it will not interfere with any "live"
data.

ZODB layers can be found in the module ``plone.testing.zodb``. If you depend
on this, you can use the ``[zodb]`` extra when depending on ``plone.testing``.

Empty ZODB sandbox
~~~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.zodb.EMPTY_ZODB`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.zodb.EmptyZODB`` |
+------------+--------------------------------------------------+
| Bases: | None |
+------------+--------------------------------------------------+
| Resources: | ``zodbDB`` |
| +--------------------------------------------------+
| | ``zodbDB`` (test set-up only) |
| +--------------------------------------------------+
| | ``zodbConnection`` (test set-up only) |
+------------+--------------------------------------------------+

This layer sets up a simple ZODB sandbox using ``DemoStorage``. The ZODB root
object is a simple persistent mapping, available as the resource ``zodbRoot``.
The ZODB database object is available as the resource ``zodbDB``. The
connection used in the test is available as ``zodbConnection``.

Note that the ``zodbConnection`` and ``zodbRoot`` resources are created and
destroyed for each test. You can use ``zodbDB`` (and the ``open()`` method)
if you are writing a layer based on this one and need to set up a fixture
during layer set up. Don't forget to close the connection before concluding
the test setup!

A new transaction is begun for each test, and rolled back (aborted) on test
tear-down. This means that so long as you don't use ``transaction.commit()``
explicitly in your code, it should be safe to add or modify items in the
ZODB root.

If you want to create a test fixture with persistent data in your own layer
based on ``EMPTY_ZODB``, you can use the following pattern::

from plone.layer import Layer
from plone.layer import zodb

class MyLayer(Layer):
defaultBases = (zodb.EMPTY_ZODB,)

def setUp(self):

import transaction
self['zodbDB'] = db = zodb.stackDemoStorage(self.get('zodbDB'), name='MyLayer')

conn = db.open()
root = conn.root()

# modify the root object here

transaction.commit()
conn.close()

def tearDown(self):

self['zodbDB'].close()
del self['zodbDB']

This shadows the ``zodbDB`` resource with a new database that uses a new
``DemoStorage`` stacked on top of the underlying database storage. The fixture
is added to this storage and committed during layer setup. (The base layer
test set-up/tear-down will still begin and abort a new transaction for each
*test*). On layer tear-down, the database is closed and the resource popped,
leaving the original ``zodbDB`` database with the original, pristine storage.

Helper functions
~~~~~~~~~~~~~~~~

One helper function is available in the ``plone.testing.zodb`` module.

``stackDemoStorage(db=None, name=None)``
Create a new ``DemoStorage`` using the storage from the passed-in database
as a base. If ``db`` is None, a brand new storage is created.

A ``name`` can be given to uniquely identify the storage. It is optional,
but it is often useful for debugging purposes to pass the name of the
layer.

The usual pattern is::

def setUp(self):
self['zodbDB'] = zodb.stackDemoStorage(self.get('zodbDB'), name='MyLayer')

def tearDown(self):
self['zodbDB'].close()
del self['zodbDB']

This will shadow the ``zodbDB`` resource with an isolated
``DemoStorage``, creating a new one if that resource does not already
exist. All existing data continues to be available, but new changes are
written to the stacked storage. On tear-down, the stacked database is
closed and the resource removed, leaving the original data.

Zope 2
------

The Zope 2 layers provide test fixtures suitable for testing Zope 2
applications. They set up a Zope 2 application root, install core Zope 2
products, and manage security.

Zope 2 layers can be found in the module ``plone.testing.z2``. If you depend
on this, you can use the ``[z2]`` extra when depending on ``plone.testing``.

Startup
~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.z2.STARTUP`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.z2.Startup`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.zca.LAYER_CLEANUP`` |
+------------+--------------------------------------------------+
| Resources: | ``zodbDB`` |
| +--------------------------------------------------+
| | ``configurationContext`` |
| +--------------------------------------------------+
| | ``host`` |
| +--------------------------------------------------+
| | ``port`` |
+------------+--------------------------------------------------+

This layer sets up a Zope 2 environment, and is a required base for all other
Zope 2 layers. You cannot run two instances of this layer in parallel, since
Zope 2 depends on some module-global state to run, which is managed by this
layer.

On set-up, the layer will configure a Zope environment with:

**Note:** The ``STARTUP`` layer is a useful base layer for your own fixtures,
but should not be used directly, since it provides no test lifecycle or
transaction management. See the "Integration test" and "Functional" test
sections below for examples of how to create your own layers.

* Debug mode enabled.
* ZEO client cache disabled.
* Some patches installed, which speed up Zope startup by disabling the help
system and some other superfluous aspects of Zope.
* One thread (this only really affects the ``ZSERVER`` and ``FTP_SERVER``
layers).
* A pristine database using ``DemoStorage``, exposed as the resource
``zodbDB``. Zope is configured to use this database in a way that will
also work if the ``zodbDB`` resource is shadowed using the pattern shown
above in the description of the ``zodb.EMPTY_ZODB`` layer.
* A fake hostname and port, exposed as the ``host`` and ``port`` resource,
respectively.
* A minimal set of products installed (``Products.OFSP`` and
``Products.PluginIndexes``, both required for Zope to start up).
* A stacked ZCML configuration context, exposed as the resource
``configurationContext``. As illustrated above, you should use the
``zca.stackConfigurationContext()`` helper to stack your own configuration
context if you use this.
* A minimal set of global Zope components configured.

Note that unlike a "real" Zope site, products in the ``Products.*`` namespace
are not automatically loaded, nor is any ZCML.

Integration test
~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.z2.INTEGRATION_TESTING`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.z2.IntegrationTest`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.z2.STARTUP`` |
+------------+--------------------------------------------------+
| Resources: | ``app`` |
| +--------------------------------------------------+
| | ``request`` |
+------------+--------------------------------------------------+

This layer is intended for integration testing against the simple ``STARTUP``
fixture. If you want to create your own layer with a more advanced, shared
fixture, see "Integration and functional testing with custom fixtures" below.

For each test, it exposes the Zope application root as the resource ``app``.
This is wrapped in the request container, so you can do ``app.REQUEST`` to
acquire a fake request, but the request is also available as the resource
``request``.

A new transaction is begun for each test and rolled back on test tear-down,
meaning that so long as the code under test does not explicitly commit any
changes, the test may modify the ZODB.

*Hint:* If you want to set up a persistent test fixture in a layer based
on this one (or ``z2.FUNCTIONAL_TESTING``), you can stack a new
``DemoStorage`` in a shadowing ``zodbDB`` resource, using the pattern
described above for the ``zodb.EMPTY_ZODB`` layer.

Once you've shadowed the ``zodbDB`` resource, you can do (e.g. in your
layer's ``setUp()`` method)::

...
with z2.zopeApp() as app:
# modify the Zope application root

The ``zopeApp()`` context manager will open a new connection to the Zope
application root, accessible here as ``app``. Provided the code within
the ``with`` block does not raise an exception, the transaction will be
committed and the database closed properly upon exiting the block.

Functional testing
~~~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.z2.FUNCTIONAL_TESTING`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.z2.FunctionalTest`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.z2.STARTUP`` |
+------------+--------------------------------------------------+
| Resources: | ``app`` |
| +--------------------------------------------------+
| | ``request`` |
+------------+--------------------------------------------------+

This layer is intended for functional testing against the simple ``STARTUP``
fixture. If you want to create your own layer with a more advanced, shared
fixture, see "Integration and functional testing with custom fixtures" below.

As its name implies, this layer is intended mainly for functional end-to-end
testing using tools like `zope.testbrowser`_. See also the ``Browser`` object
as described under "Helper functions" below.

This layer is very similar to ``INTEGRATION_TESTING``, but is not based on it.
It sets up the same fixture and exposes the same resources. However, instead
of using a simple transaction abort to isolate the ZODB between tests, it uses
a stacked ``DemoStorage`` for each test. This is slower, but allows test code
to perform and explicit commit, as will usually happen in a functional test.

Integration and functional testing with custom fixtures
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you want to extend the ``STARTUP`` fixture for use with integration or
functional testing, you should use the following pattern:

* Create a layer class and a "fixture" base layer instance that has
``z2.STARTUP`` (or some intermediary layer, such as ``z2.ZSERVER_FIXTURE``
or ``z2.FTP_SERVER_FIXTURE``, shown below) as a base.
* Create "end user" layers by instantiating the ``z2.IntegrationTesting``
and/or ``FunctionalTesting`` classes with this new "fixture" layer as a
base.

This allows the same fixture to be used regardless of the "style" of testing,
minimising the amount of set-up and tear-down. The "fixture" layers manage the
fixture as part of the *layer* lifecycle. The layer class
(``IntegrationTesting`` or ``FunctionalTesting``), manages the *test*
lifecycle, and the test lifecycle only.

For example::

from plone.testing import Layer, z2, zodb

class MyLayer(Layer):
defaultBases = (z2.STARTUP,)

def setUp(self):
# Set up the fixture here
...

def tearDown(self):
# Tear down the fixture here
...

MY_FIXTURE = MyLayer()

MY_INTEGRATION_TESTING = z2.IntegrationTesting(bases=(MY_FIXTURE,), name="MyFixture:Integration")
MY_FUNCTIONAL_TESTING = z2.FunctionalTesting(bases=(MY_FIXTURE,), name="MyFixture:Functional")

(Note that we need to give an explicit, unique name to the two layers that
re-use the ``IntegrationTesting`` and ``FunctionalTesting`` classes.)

In this example, other layers could extend the "MyLayer" fixture by using
``MY_FIXTURE`` as a base. Tests would use either ``MY_INTEGRATION_TESTING``
or ``MY_FUNCTIONAL_TESTING`` as appropriate. However, even if both these two
layers were used, the fixture in ``would``MY_FIXTURE`` only be set up once.

**Note:** If you implement the ``testSetUp()`` and ``testTearDown()`` test
lifecycle methods in your "fixture" layer (e.g. in the the ``MyLayer``
class above), they will execute before the corresponding methods from
``IntegrationTesting`` and ``FunctionalTesting``. Hence, they cannot use
those layers' resources (``app`` and ``request``).

It may be preferable, therefore, to have your own "test lifecycle" layer
classes that subclass ``IntegrationTesting`` and/or ``FunctionalTesting`` and
call base class methods as appropriate. ``plone.app.testing`` takes this
approach, for example.

HTTP ZServer thread (fixture only)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.z2.ZSERVER_FIXTURE`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.z2.ZServer`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.z2.STARTUP`` |
+------------+--------------------------------------------------+
| Resources: | ``host`` |
| +--------------------------------------------------+
| | ``port`` |
+------------+--------------------------------------------------+

This layer extends the ``z2.STARTUP`` layer to start the Zope HTTP server in
a separate thread. This means the test site can be accessed through a web
browser, and can thus be used with tools like `Windmill`_ or `Selenium`_.

**Note:** This layer is useful as a fixture base layer only, because it does
not manage the test lifecycle. Use the ``ZSERVER`` layer if you want to
execute functional tests against this fixture.

The ZServer's hostname (normally ``localhost``) is available through the
resource ``host``, whilst the port it is running on is available through the
resource ``port``.

*Hint:* Whilst the layer is set up, you can actually access the test Zope
site through a web browser. The default URL will be
``http://localhost:55001``.

HTTP ZServer functional testing
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.z2.ZSERVER`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.z2.FunctionalTesting`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.z2.ZSERVER_FIXTURE`` |
+------------+--------------------------------------------------+
| Resources: | |
+------------+--------------------------------------------------+

This layer provides the functional testing lifecycle against the fixture set
up by the ``z2.ZSERVER_FIXTURE`` layer.

You can use this to run "live" functional tests against a basic Zope site.
You should **not** use it as a base. Instead, create your own "fixture"
layer that extends ``z2.ZSERVER_FIXTURE``, and then instantiate the
``FunctionalTesting`` class with this extended fixture layer as a base,
as outlined above.

FTP server thread (fixture only)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.z2.FTP_SERVER_FIXTURE`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.z2.FTPServer`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.z2.STARTUP`` |
+------------+--------------------------------------------------+
| Resources: | ``host`` |
| +--------------------------------------------------+
| | ``port`` |
+------------+--------------------------------------------------+

This layer is the FTP server equivalent of the ``ZSERVER_FIXTURE`` layer. It
can be used to functionally test Zope servers.

**Note:** This layer is useful as a fixture base layer only, because it does
not manage the test lifecycle. Use the ``FTP_SERVER`` layer if you want to
execute functional tests against this fixture.

*Hint:* Whilst the layer is set up, you can actually access the test Zope
site through an FTP client. The default URL will be
``ftp://localhost:55002``.

**Warning:** Do not run the ``FTP_SERVER`` and ``ZSERVER`` layers
concurrently in the same process.

If you need both ZServer and FTPServer running together, you can subclass the
``ZServer`` layer class (like the ``FTPServer`` layer class does) and
implement the ``setUpServer()`` and ``tearDownServer()`` methods to set up
and close down two servers on different ports. They will then share a main
loop.

FTP server functional testing
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+------------+--------------------------------------------------+
| Layer: | ``plone.testing.z2.FTP_SERVER`` |
+------------+--------------------------------------------------+
| Class: | ``plone.testing.z2.FunctionalTesting`` |
+------------+--------------------------------------------------+
| Bases: | ``plone.testing.z2.FTP_SERVER_FIXTURE`` |
+------------+--------------------------------------------------+
| Resources: | |
+------------+--------------------------------------------------+

This layer provides the functional testing lifecycle against the fixture set
up by the ``z2.FTP_SERVER_FIXTURE`` layer.

You can use this to run "live" functional tests against a basic Zope site.
You should **not** use it as a base. Instead, create your own "fixture"
layer that extends ``z2.FTP_SERVER_FIXTURE``, and then instantiate the
``FunctionalTesting`` class with this extended fixture layer as a base,
as outlined above.

Helper functions
~~~~~~~~~~~~~~~~

Several helper functions are available in the ``plone.testing.z2`` module.

``zopeApp(db=None, conn=Non, environ=None)``
This function can be used as a context manager for any code that requires
access to the Zope application root. By using it in a ``with`` block,
the database will be opened, and the application root will be obtained and
request-wrapped. When exiting the ``with`` block, the transaction will be
committed and the database properly closed, unless an exception was
raised::

with z2.zopeApp() as app:
# do something with app

If you want to use a specific database or database connection, pass either
the ``db`` or ``conn`` arguments. If the context manager opened a new
connection, it will close it, but it will not close a connection passed
with ``conn``.

To set keys in the (fake) request environment, pass a dictionary of
environment values as ``environ``.

Note that ``zopeApp()`` should *not* normally be used in tests or test
set-up/tear-down, because the ``INTEGRATOIN_TEST`` and
``FUNCTIONAL_TESTING`` layers both manage the application root (as the
``app`` resource) and close it for you. It is very useful in layer setup,
however.
``installProduct(app, product, quiet=False)``
Install a Zope 2 style product, ensuring that its ``initialize()``
function is called. The product name must be the full dotted name, e.g.
``plone.app.portlets`` or ``Products.CMFCore``. If ``quiet`` is true,
duplicate registrations will be ignored silently, otherwise a message is
logged.

To get hold of the application root, passed as the ``app`` argument, you
would normally use the ``zopeApp()`` context manager outlined above.
``uninstallProduct(app, product, quiet=False)``
This is the reciprocal of ``installProduct()``, normally used during layer
tear-down. Again, you should use ``zopeApp()`` to obtain the application
root.
``login(userFolder, userName)``
Create a new security manager that simulates being logged in as the given
user. ``userFolder`` is an ``acl_users`` object, e.g.
``app['acl_users']`` for the root user folder.
``logout()``
Simulate being the anonymous user by unsetting the security manager.
``setRoles(userFolder, userName, roles)``
Set the roles of the given user in the given user folder to the given
list of roles.
``addRequestContainer(app, environ=None)``
Create a fake request and wrap the given object (normally an application
root) in a ``RequestContainer`` with this request. This makes acquisition
of ``app.REQUEST`` possible. To initialise the request environment with
non-default values, pass a dictionary as ``environ``.

Note that this method is rarely used, because both the ``zopeApp()``
context manager and the layer set-up/tear-down for
``z2.INTEGRATION_TESTING`` and ``z2.FUNCTIONAL_TESTING`` will wrap the
``app`` object before exposing it.
``Browser(app)``
Obtain a test browser client, for use with `zope.testbrowser`_. You should
use this in conjunction with the ``z2.FUNCTIONAL_TESTING`` layer or a
derivative. You must pass the app root, usually obtained from the ``app``
resource of the layer, e.g.::

app = self.layer['app']
browser = z2.Browser(app)

You can then use ``browser`` as described in the `zope.testbrowser`_
documentation.

Bear in mind that the test browser runs separately from the test fixture.
In particular, calls to helpers such as ``login()`` or ``logout()`` do
not affect the state that the test browser sees. If you want to set up
a persistent fixture (e.g. test content), you can do so before creating
the test browser, but you will need to explicitly commit your changes,
with::

import transaction
transaction.commit()

.. _zope.testing: http://pypi.python.org/pypi/zope.testing
.. _zope.testbrowser: http://pypi.python.org/pypi/zope.testbrowser
.. _zope.component: http://pypi.python.org/pypi/zope.component
.. _zope.publisher: http://pypi.python.org/pypi/zope.publisher
.. _plone.app.testing: http://pypi.python.org/pypi/plone.app.testing
.. _zc.recipe.testrunner: http://pypi.python.org/pypi/zc.recipe.testrunner
.. _coverage: http://pypi.python.org/pypi/coverage
.. _Cobertura: http://wiki.hudson-ci.org/display/HUDSON/Cobertura+Plugin
.. _Hudson: http://www.hudson-labs.org/
.. _unittest: http://doc.python.org/library/unittest.html
.. _unittest2: http://pypi.python.org/pypi/unittest2
.. _doctest: http://docs.python.org/dev/library/doctest.html
.. _Windmill: http://getwindmill.com/
.. _Selenium: http://seleniumhq.org/


Changelog
=========

4.0a5 (2011-03-02)
------------------

- Handle test failures due to userFolderAddUser returning the user object in
newer versions of Zope.
[esteele]

- Add ``setUpZcmlFiles`` and ``tearDownZcmlFiles`` helpers to enable loading
of ZCML files without too much boilerplate.
[gotcha]

- Add some logging.
[gotcha]

- Add the ``[security]`` extra, to provide tear-down of security checkers.
[optilude]

- Let the ``IntegrationTesting`` and ``FunctionalTesting`` lifecycle layers
set up request ``PARENTS`` and, if present, wire up
``zope.globalrequest``.
[optilude]

- Make the test browser support IStreamIterators
[optilue]

4.0a4 (2011-01-11)
------------------

- Make sure ZCML doesn't load during App startup in Zope 2.13.
[davisagli]

4.0a3 (2010-12-14)
------------------

- Ignore the `testinghome` configuration setting if present.
[stefan]

- Use the new API for getting the packages_to_initialize list in Zope 2.13.
[davisagli]

- De-duplicate _register_monkies and _meta_type_regs in the correct module on
teardown of the Startup layer in Zope 2.13.
[davisagli]

- Allow doctest suites from `zope.testing` to work with
`plone.testing.layer.layered`. Previously, only doctest suites from
the stdlib would see the `layer` global.
[nouri]

- Changed documentation to advertise the `coverage` library for running
coverage tests instead of the built-in `zope.testing` support. This also
avoids using `z3c.coverage`. The coverage tests now run at the same speed
as a normal test run, making it more likely to get executed frequently.
[hannosch]

- Correct license to GPL version 2 only.
[hannosch]

- Fix some user id vs name confusion.
[rossp]

- Add the option to specify ZServer host and port through environment
variables (ZSERVER_HOST and ZSERVER_PORT).
[esteele]

1.0a2 - 2010-09-05
------------------

- Fix a problem that would cause ``<meta:redefinePermission />`` to break.
In particular fixes the use of the ``zope2.Public`` permission.
[optilude]

- Set the security implementation to "Python" for easier debugging during
the z2.STARTUP layer.
[optilude]

- Initialize Five in the z2.Startup layer, pushing a
Zope2VocabularyRegistry on layer set-up and restoring the previous
one upon tear-down.
[dukebody]

1.0a1 - 2010-08-01
------------------

- Initial release


Detailed documentation
======================

Layer base class
----------------

This package provides a layer base class which can be used by the test
runner. It is available as a convenience import from the package root.

>>> from plone.testing import Layer

A layer may be instantiated directly, though in this case the ``name``
argument is required (see below).

>>> NULL_LAYER = Layer(name="Null layer")

This is not very useful on its own. It has an empty list of bases, and each of
the layer lifecycle methods does nothing.

>>> NULL_LAYER.__bases__
()
>>> NULL_LAYER.__name__
'Null layer'
>>> NULL_LAYER.__module__
'plone.testing.layer'

>>> NULL_LAYER.setUp()
>>> NULL_LAYER.testSetUp()
>>> NULL_LAYER.tearDown()
>>> NULL_LAYER.testTearDown()

Just about the only reason to use this directly (i.e. not as a base class) is
to group together other layers.

>>> SIMPLE_LAYER = Layer(bases=(NULL_LAYER,), name="Simple layer", module='plone.testing.tests')

Here, we've also set the module name directly. The default for all layers is
to take the module name from the stack frame where the layer was instantiated.
In doctests, that doesn't work, though, so we fall back on the module name of
the layer class. The two are often the same, of course.

This layer now has the bases, name and module we set:

>>> SIMPLE_LAYER.__bases__
(<Layer 'plone.testing.layer.Null layer'>,)

>>> SIMPLE_LAYER.__name__
'Simple layer'

>>> SIMPLE_LAYER.__module__
'plone.testing.tests'

The ``name`` argument is required when using ``Layer`` directly (but not
when using a subclass):

>>> Layer((SIMPLE_LAYER,))
Traceback (most recent call last):
...
ValueError: The `name` argument is required when instantiating `Layer` directly

>>> class NullLayer(Layer):
... pass
>>> NullLayer()
<Layer '__builtin__.NullLayer'>

Using ``Layer`` as a base class
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The usual pattern is to use ``Layer`` as a base class for a custom layer.
This can then override the lifecycle methods as appropriate, as well as
set a default list of bases.

>>> class BaseLayer(Layer):
...
... def setUp(self):
... print "Setting up base layer"
...
... def tearDown(self):
... print "Tearing down base layer"

>>> BASE_LAYER = BaseLayer()

The layer name and module are taken from the class.

>>> BASE_LAYER.__bases__
()
>>> BASE_LAYER.__name__
'BaseLayer'
>>> BASE_LAYER.__module__
'__builtin__'

We can now create a new layer that has this one as a base. We can do this in
the instance constructor, as shown above, but the most common pattern is to
set the default bases in the class body, using the variable ``defaultBases``.

We'll also set the default name explicitly here by passing a name to the the
super-constructor. This is mostly cosmetic, but may be desirable if the class
name would be misleading in the test runner output.

>>> class ChildLayer(Layer):
... defaultBases = (BASE_LAYER,)
...
... def __init__(self, bases=None, name='Child layer', module=None):
... super(ChildLayer, self).__init__(bases, name, module)
...
... def setUp(self):
... print "Setting up child layer"
...
... def tearDown(self):
... print "Tearing down child layer"

>>> CHILD_LAYER = ChildLayer()

Notice how the bases have now been set using the value in ``defaultBases``.

>>> CHILD_LAYER.__bases__
(<Layer '__builtin__.BaseLayer'>,)
>>> CHILD_LAYER.__name__
'Child layer'
>>> CHILD_LAYER.__module__
'__builtin__'

Overriding the default list of bases
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We can override the list of bases on a per-instance basis. This may be
dangerous, i.e. the layer is likely to expect that its bases are set up.
Sometimes, it may be useful to inject a new base, however, especially when
re-using layers from other packages.

The new list of bases is passed to the constructor. When creating a second
instance of a layer (most layers are global singletons created only once),
it's useful to give the new instance a unique name, too.

>>> NEW_CHILD_LAYER = ChildLayer(bases=(SIMPLE_LAYER, BASE_LAYER,), name='New child')

>>> NEW_CHILD_LAYER.__bases__
(<Layer 'plone.testing.tests.Simple layer'>, <Layer '__builtin__.BaseLayer'>)
>>> NEW_CHILD_LAYER.__name__
'New child'
>>> NEW_CHILD_LAYER.__module__
'__builtin__'

Inconsistent bases
~~~~~~~~~~~~~~~~~~

Layer bases are maintained in an order that is semantically equivalent to the
"method resolution order" Python maintains for base classes. We can get this
from the ``baseResolutionOrder`` attribute:

>>> CHILD_LAYER.baseResolutionOrder
(<Layer '__builtin__.Child layer'>, <Layer '__builtin__.BaseLayer'>)

>>> NEW_CHILD_LAYER.baseResolutionOrder
(<Layer '__builtin__.New child'>, <Layer 'plone.testing.tests.Simple layer'>,
<Layer 'plone.testing.layer.Null layer'>,
<Layer '__builtin__.BaseLayer'>)

As with Python classes, it is possible to construct an invalid set of bases.
In this case, layer instantiation will fail.

>>> INCONSISTENT_BASE1 = Layer(name="Inconsistent 1")
>>> INCONSISTENT_BASE2 = Layer((INCONSISTENT_BASE1,), name="Inconsistent 1")
>>> INCONSISTENT_BASE3 = Layer((INCONSISTENT_BASE1, INCONSISTENT_BASE2,), name="Inconsistent 1")
Traceback (most recent call last):
...
TypeError: Inconsistent layer hierarchy!

Using the resource manager
~~~~~~~~~~~~~~~~~~~~~~~~~~

Layers are also resource managers. Resources can be set, retrieved and
deleted using dictionary syntax. Resources in base layers are available in
child layers. When an item is set on a child layer, it shadows any items with
the same key in any base layer (until it is deleted), but the original item
still exists.

Let's create a somewhat complex hierarchy of layers that all set resources
under a key ``'foo'`` in their ``setUp()`` methods.

>>> class Layer1(Layer):
... def setUp(self):
... self['foo'] = 1
... def tearDown(self):
... del self['foo']
>>> LAYER1 = Layer1()

>>> class Layer2(Layer):
... defaultBases = (LAYER1,)
... def setUp(self):
... self['foo'] = 2
... def tearDown(self):
... del self['foo']
>>> LAYER2 = Layer2()

>>> class Layer3(Layer):
... def setUp(self):
... self['foo'] = 3
... def tearDown(self):
... del self['foo']
>>> LAYER3 = Layer3()

>>> class Layer4(Layer):
... defaultBases = (LAYER2, LAYER3,)
... def setUp(self):
... self['foo'] = 4
... def tearDown(self):
... del self['foo']
>>> LAYER4 = Layer4()

**Important:** Resources that are created in ``setUp()`` must be deleted
in ``tearDown()``. Similarly, resources created in ``testSetUp()`` must
be deleted in ``testTearDown()``. This ensures resources are properly
stacked and do not leak between layers.

If a test was using ``LAYER4``, the test runner would call each setup step in
turn, starting with the "deepest" layer. We'll simulate that here, so that
each of the resources is created.

>>> LAYER1.setUp()
>>> LAYER2.setUp()
>>> LAYER3.setUp()
>>> LAYER4.setUp()

The layers are ordered in a known "resource resolution order", which is used
to determine in which order the layers shadow one another. This is based on
the same algorithm as Python's method resolution order.

>>> LAYER4.baseResolutionOrder
(<Layer '__builtin__.Layer4'>,
<Layer '__builtin__.Layer2'>,
<Layer '__builtin__.Layer1'>,
<Layer '__builtin__.Layer3'>)

When fetching and item from a layer, it will be obtained according to the
resource resolution order.

>>> LAYER4['foo']
4

This is not terribly interesting, since ``LAYER4`` has the resource ``'foo'``
set directly. Let's tear down the layer (which deletes the resource) and see
what happens.

>>> LAYER4.tearDown()
>>> LAYER4['foo']
2

We can continue up the chain:

>>> LAYER2.tearDown()
>>> LAYER4['foo']
1

>>> LAYER1.tearDown()
>>> LAYER4['foo']
3

Once we've deleted the last key, we'll get a ``KeyError``:

>>> LAYER3.tearDown()
>>> LAYER4['foo']
Traceback (most recent call last):
...
KeyError: 'foo'

To guard against this, we can use the ``get()`` method.

>>> LAYER4.get('foo', -1)
-1

We can also test with 'in':

>>> 'foo' in LAYER4
False

To illustrate that this indeed works, let's set the resource back on one
of the bases.

>>> LAYER3['foo'] = 10
>>> LAYER4.get('foo', -1)
10

Let's now consider a special case: a base layer sets up a resource in layer
setup, and uses it in test setup. A child layer then shadows this resource in
its own layer setup method. In this case, we want the base layer's
``testSetUp()`` to use the shadowed version that the child provided.

(This is similar to how instance variables work: a base class may set an
attribute on ``self`` and use it in a method. If a subclass then sets the same
attribute to a different value and the base class method is called on an
instance of the subclass, the base class attribute is used).

*Hint:* If you definitely need to access the "original" resource in your
``testSetUp()``/``testTearDown()`` methods, you can store a reference to
the resource as a layer instance variable::

self.someResource = self['someResource'] = SomeResource()

``self.someResource`` will now be the exact resource created here, whereas
``self['someResource']`` will retain the layer shadowing semantics. In
most cases, you probably *don't* want to do this, allowing child layers to
supply overridden versions of resources as appropriate.

First, we'll create some base layers. We want to demonstrate having two
"branches" of bases that both happen to define the same resource.

>>> class ResourceBaseLayer1(Layer):
... def setUp(self):
... self['resource'] = "Base 1"
... def testSetUp(self):
... print self['resource']
... def tearDown(self):
... del self['resource']

>>> RESOURCE_BASE_LAYER1 = ResourceBaseLayer1()

>>> class ResourceBaseLayer2(Layer):
... defaultBases = (RESOURCE_BASE_LAYER1,)
... def testSetUp(self):
... print self['resource']

>>> RESOURCE_BASE_LAYER2 = ResourceBaseLayer2()

>>> class ResourceBaseLayer3(Layer):
... def setUp(self):
... self['resource'] = "Base 3"
... def testSetUp(self):
... print self['resource']
... def tearDown(self):
... del self['resource']

>>> RESOURCE_BASE_LAYER3 = ResourceBaseLayer3()

We'll then create the child layer that overrides this resource.

>>> class ResourceChildLayer(Layer):
... defaultBases = (RESOURCE_BASE_LAYER2, RESOURCE_BASE_LAYER3)
... def setUp(self):
... self['resource'] = "Child"
... def testSetUp(self):
... print self['resource']
... def tearDown(self):
... del self['resource']

>>> RESOURCE_CHILD_LAYER = ResourceChildLayer()

We'll first set up the base layers on their own and simulate two tests.

A test with RESOURCE_BASE_LAYER1 only would look like this:

>>> RESOURCE_BASE_LAYER1.setUp()

>>> RESOURCE_BASE_LAYER1.testSetUp()
Base 1
>>> RESOURCE_BASE_LAYER1.testTearDown()

>>> RESOURCE_BASE_LAYER1.tearDown()

A test with RESOURCE_BASE_LAYER2 would look like this:

>>> RESOURCE_BASE_LAYER1.setUp()
>>> RESOURCE_BASE_LAYER2.setUp()

>>> RESOURCE_BASE_LAYER1.testSetUp()
Base 1
>>> RESOURCE_BASE_LAYER2.testSetUp()
Base 1
>>> RESOURCE_BASE_LAYER2.testTearDown()
>>> RESOURCE_BASE_LAYER1.testTearDown()

>>> RESOURCE_BASE_LAYER2.tearDown()
>>> RESOURCE_BASE_LAYER1.tearDown()

A test with RESOURCE_BASE_LAYER3 only would look like this:

>>> RESOURCE_BASE_LAYER3.setUp()

>>> RESOURCE_BASE_LAYER3.testSetUp()
Base 3
>>> RESOURCE_BASE_LAYER3.testTearDown()

>>> RESOURCE_BASE_LAYER3.tearDown()

Now let's set up the child layer and simulate another test. We should now be
using the shadowed resource.

>>> RESOURCE_BASE_LAYER1.setUp()
>>> RESOURCE_BASE_LAYER2.setUp()
>>> RESOURCE_BASE_LAYER3.setUp()
>>> RESOURCE_CHILD_LAYER.setUp()

>>> RESOURCE_BASE_LAYER1.testSetUp()
Child
>>> RESOURCE_BASE_LAYER2.testSetUp()
Child
>>> RESOURCE_BASE_LAYER3.testSetUp()
Child
>>> RESOURCE_CHILD_LAYER.testSetUp()
Child

>>> RESOURCE_CHILD_LAYER.testTearDown()
>>> RESOURCE_BASE_LAYER3.testTearDown()
>>> RESOURCE_BASE_LAYER2.testTearDown()
>>> RESOURCE_BASE_LAYER1.testTearDown()

Finally, we'll tear down the child layer again and simulate another test.
we should have the original resources back. Note that the first and third
layers no longer share a resource, since they don't have a common ancestor.

>>> RESOURCE_CHILD_LAYER.tearDown()

>>> RESOURCE_BASE_LAYER1.testSetUp()
Base 1
>>> RESOURCE_BASE_LAYER2.testSetUp()
Base 1
>>> RESOURCE_BASE_LAYER2.testTearDown()
>>> RESOURCE_BASE_LAYER1.testTearDown()

>>> RESOURCE_BASE_LAYER3.testSetUp()
Base 3
>>> RESOURCE_BASE_LAYER3.testTearDown()

Finally, we'll tear down the remaining layers..

>>> RESOURCE_BASE_LAYER3.tearDown()
>>> RESOURCE_BASE_LAYER2.tearDown()
>>> RESOURCE_BASE_LAYER1.tearDown()

Asymmetric deletion
+++++++++++++++++++

It is an error to create or shadow a resource in a set-up lifecycle method and
not delete it again in the tear-down. It is also an error to delete a resource
that was not explicitly created. These two layers break those roles:

>>> class BadLayer1(Layer):
... def setUp(self):
... pass
... def tearDown(self):
... del self['foo']
>>> BAD_LAYER1 = BadLayer1()

>>> class BadLayer2(Layer):
... defaultBases = (BAD_LAYER1,)
... def setUp(self):
... self['foo'] = 1
... self['bar'] = 2
>>> BAD_LAYER2 = BadLayer2()

Let's simulate a test that uses ``BAD_LAYER2``:

>>> BAD_LAYER1.setUp()
>>> BAD_LAYER2.setUp()

>>> BAD_LAYER1.testSetUp()
>>> BAD_LAYER2.testSetUp()

>>> BAD_LAYER2.testTearDown()
>>> BAD_LAYER1.testTearDown()

>>> BAD_LAYER2.tearDown()
>>> BAD_LAYER1.tearDown()
Traceback (most recent call last):
...
KeyError: 'foo'

Here, we've got an error in the base layer. This is because the resource
is actually associated with the layer that first created it, in this case
``BASE_LAYER2``. This one remains intact and orphaned:

>>> 'foo' in BAD_LAYER2._resources
True
>>> 'bar' in BAD_LAYER2._resources
True

Doctest layer helper
~~~~~~~~~~~~~~~~~~~~

The ``doctest`` module is not aware of ``zope.testing``'s layers concept.
Therefore, the syntax for creating a doctest with a layer and adding it to
a test suite is somewhat contrived: the test suite has to be created first,
and then the layer attribute set on it:

>>> class DoctestLayer(Layer):
... pass
>>> DOCTEST_LAYER = DoctestLayer()

>>> import unittest2 as unittest
>>> import doctest

>>> def test_suite():
... suite = unittest.TestSuite()
... layerDoctest = doctest.DocFileSuite('layer.txt', package='plone.testing')
... layerDoctest.layer = DOCTEST_LAYER
... suite.addTest(layerDoctest)
... return suite

>>> suite = test_suite()
>>> tests = list(suite)
>>> len(tests)
1
>>> tests[0].layer is DOCTEST_LAYER
True


To make this a little easier - especially when setting up multiple tests -
a helper function called ``layered`` is provided:

>>> from plone.testing import layered

>>> def test_suite():
... suite = unittest.TestSuite()
... suite.addTests([
... layered(doctest.DocFileSuite('layer.txt', package='plone.testing'), layer=DOCTEST_LAYER),
... # repeat with more suites if necessary
... ])
... return suite

This does the same as the sample above.

>>> suite = test_suite()
>>> tests = list(suite)
>>> len(tests)
1
>>> tests[0].layer is DOCTEST_LAYER
True

In addition, a 'layer' glob is added to each test in the suite. This allows
the test to access layer resources.

>>> len(list(tests[0]))
1
>>> list(tests[0])[0]._dt_test.globs['layer'] is DOCTEST_LAYER
True


Zope Component Architecture layers
----------------------------------

The ZCA layers are found in the module ``plone.testing.zca``:

>>> from plone.testing import zca

For testing, we need a testrunner

>>> from zope.testing.testrunner import runner

Unit testing
~~~~~~~~~~~~

The ``UNIT_TESTING`` layer is used to set up a clean component registry
between each test. It uses ``zope.testing.cleanup`` to clean up all global
state.

It has no bases:

>>> "%s.%s" % (zca.UNIT_TESTING.__module__, zca.UNIT_TESTING.__name__,)
'plone.testing.zca.UnitTesting'

>>> zca.UNIT_TESTING.__bases__
()

The component registry is cleaned up between each test.

>>> from zope.interface import Interface
>>> from zope.component import provideUtility

>>> class DummyUtility(object):
... def __init__(self, name):
... self.name = name
... def __repr__(self):
... return "<%s>" % self.name

>>> provideUtility(DummyUtility("Dummy"), provides=Interface, name="test-dummy")

>>> from zope.component import queryUtility
>>> queryUtility(Interface, name="test-dummy")
<Dummy>

Layer setup does nothing.

>>> options = runner.get_options([], [])
>>> setupLayers = {}
>>> runner.setup_layer(options, zca.UNIT_TESTING, setupLayers)
Set up plone.testing.zca.UnitTesting in ... seconds.

Let's now simulate a test. Before any test setup has happened, our previously
registered utility is still there.

>>> queryUtility(Interface, name="test-dummy")
<Dummy>

On test setup, it disappears.

>>> zca.UNIT_TESTING.testSetUp()

>>> queryUtility(Interface, name="test-dummy") is None
True

The test would now execute. It may register some components.

>>> provideUtility(DummyUtility("Dummy2"), provides=Interface, name="test-dummy")
>>> queryUtility(Interface, name="test-dummy")
<Dummy2>

On test tear-down, this disappears.

>>> zca.UNIT_TESTING.testTearDown()

>>> queryUtility(Interface, name="test-dummy") is None
True

Layer tear-down does nothing.

>>> runner.tear_down_unneeded(options, [], setupLayers)
Tear down plone.testing.zca.UnitTesting in ... seconds.

Event testing
~~~~~~~~~~~~~

The ``EVENT_TESTING`` layer extends the ``UNIT_TESTING`` layer to add the
necessary registrations for ``zope.component.eventtesting`` to work.

>>> "%s.%s" % (zca.EVENT_TESTING.__module__, zca.EVENT_TESTING.__name__,)
'plone.testing.zca.EventTesting'

>>> zca.EVENT_TESTING.__bases__
(<Layer 'plone.testing.zca.UnitTesting'>,)

Before the test, the component registry is empty and ``getEvents()`` returns
nothing, even if an event is fired.

>>> from zope.component.eventtesting import getEvents

>>> class DummyEvent(object):
... def __repr__(self):
... return "<Dummy event>"

>>> from zope.event import notify
>>> notify(DummyEvent())

>>> getEvents()
[]

Layer setup does nothing.

>>> options = runner.get_options([], [])
>>> setupLayers = {}
>>> runner.setup_layer(options, zca.EVENT_TESTING, setupLayers)
Set up plone.testing.zca.UnitTesting in ... seconds.
Set up plone.testing.zca.EventTesting in ... seconds.

Let's now simulate a test. On test setup, the event testing list is emptied.

>>> zca.UNIT_TESTING.testSetUp()
>>> zca.EVENT_TESTING.testSetUp()

>>> getEvents()
[]

The test would now execute. It may fire some events, which would show up in
the event testing list.

>>> notify(DummyEvent())
>>> getEvents()
[<Dummy event>]

On test tear-down, the list is emptied again

>>> zca.EVENT_TESTING.testTearDown()
>>> zca.UNIT_TESTING.testTearDown()

>>> getEvents()
[]

Layer tear-down does nothing.

>>> runner.tear_down_unneeded(options, [], setupLayers)
Tear down plone.testing.zca.EventTesting in ... seconds.
Tear down plone.testing.zca.UnitTesting in ... seconds.

Layer cleanup
~~~~~~~~~~~~~

The ``LAYER_CLEANUP`` layer is used to set up a clean component registry
at the set-up and tear-down of a layer. It uses ``zope.testing.cleanup`` to
clean up all global state.

It has no bases:

>>> "%s.%s" % (zca.LAYER_CLEANUP.__module__, zca.LAYER_CLEANUP.__name__,)
'plone.testing.zca.LayerCleanup'

>>> zca.LAYER_CLEANUP.__bases__
()

The component registry is cleaned up on layer set-up and tear-down (but not
between tests).

>>> from zope.interface import Interface
>>> from zope.component import provideUtility

>>> class DummyUtility(object):
... def __init__(self, name):
... self.name = name
... def __repr__(self):
... return "<%s>" % self.name

>>> provideUtility(DummyUtility("Dummy"), provides=Interface, name="test-dummy")

>>> from zope.component import queryUtility
>>> queryUtility(Interface, name="test-dummy")
<Dummy>

>>> options = runner.get_options([], [])
>>> setupLayers = {}
>>> runner.setup_layer(options, zca.LAYER_CLEANUP, setupLayers)
Set up plone.testing.zca.LayerCleanup in ... seconds.

>>> queryUtility(Interface, name="test-dummy") is None
True

A sub-layer may register additional components:

>>> provideUtility(DummyUtility("Dummy2"), provides=Interface, name="test-dummy2")

Let's now simulate a test. Test setup and tear-down does nothing.

>>> zca.LAYER_CLEANUP.testSetUp()

>>> queryUtility(Interface, name="test-dummy") is None
True
>>> queryUtility(Interface, name="test-dummy2")
<Dummy2>

>>> zca.LAYER_CLEANUP.testTearDown()

>>> queryUtility(Interface, name="test-dummy") is None
True
>>> queryUtility(Interface, name="test-dummy2")
<Dummy2>

On tear-down, the registry is cleaned again.

>>> runner.tear_down_unneeded(options, [], setupLayers)
Tear down plone.testing.zca.LayerCleanup in ... seconds.

>>> queryUtility(Interface, name="test-dummy") is None
True
>>> queryUtility(Interface, name="test-dummy2") is None
True

Basic ZCML directives
~~~~~~~~~~~~~~~~~~~~~

The ``ZCML_DIRECTIVES`` layer creates a ZCML configuration context with the
basic ``zope.component`` directives available. It extends the
``LAYER_CLEANUP`` layer.

>>> "%s.%s" % (zca.ZCML_DIRECTIVES.__module__, zca.ZCML_DIRECTIVES.__name__,)
'plone.testing.zca.ZCMLDirectives'

>>> zca.ZCML_DIRECTIVES.__bases__
(<Layer 'plone.testing.zca.LayerCleanup'>,)

Before the test, we cannot use e.g. a ``<utility />`` directive without
loading the necessary ``meta.zcml`` files.

>>> from zope.configuration import xmlconfig
>>> xmlconfig.string("""\
... <configure package="plone.testing" xmlns="http://namespaces.zope.org/zope">
... <utility factory=".tests.DummyUtility" provides="zope.interface.Interface" name="test-dummy" />
... </configure>""")
Traceback (most recent call last):
...
ZopeXMLConfigurationError: File "<string>", line 2.4
ConfigurationError: ('Unknown directive', u'http://namespaces.zope.org/zope', u'utility')

Layer setup creates a configuration context we can use to load further
configuration.

>>> options = runner.get_options([], [])
>>> setupLayers = {}
>>> runner.setup_layer(options, zca.ZCML_DIRECTIVES, setupLayers)
Set up plone.testing.zca.LayerCleanup in ... seconds.
Set up plone.testing.zca.ZCMLDirectives in ... seconds.

Let's now simulate a test that uses this configuration context to load the
same ZCML string.

>>> zca.ZCML_DIRECTIVES.testSetUp()

>>> context = zca.ZCML_DIRECTIVES['configurationContext'] # would normally be self.layer['configurationContext']
>>> xmlconfig.string("""\
... <configure package="plone.testing" xmlns="http://namespaces.zope.org/zope">
... <utility factory=".tests.DummyUtility" provides="zope.interface.Interface" name="test-dummy" />
... </configure>""", context=context) is context
True

The utility is now registered:

>>> queryUtility(Interface, name="test-dummy")
<Dummy utility>

>>> zca.UNIT_TESTING.testTearDown()

Note that normally, we'd combine this with the ``UNIT_TESTING`` layer to tear
down the component architecture as well.

Layer tear-down deletes the configuration context.

>>> runner.tear_down_unneeded(options, [], setupLayers)
Tear down plone.testing.zca.ZCMLDirectives in ... seconds.

>>> zca.ZCML_DIRECTIVES.get('configurationContext', None) is None
True

Configuration registry sandboxing
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For simple unit tests, the full cleanup performed between each test using the
``UNIT_TESTING`` layer is undoubtedly the safest and most convenient way to
ensure proper isolation of tests using the global component architecture.
However, if you are writing a complex layer that sets up a lot of components,
you may wish to keep some components registered at the layer level, whilst
still allowing tests and sub-layers to register their own components in
isolation.

This is a tricky problem, because the default ZCML directives and APIs
(``provideAdapter()``, ``provideUtility()`` and so on) explicitly work on
a single global adapter registry object. To get around this, you can use two
helper methods in the ``zca`` module to push a new global component registry
before registering components, and pop the registry after. Registries are
stacked, so the components registered in a "lower" registry are automatically
available in a "higher" registry.

Let's illustrate this with a layer that stacks two new global registries. The
first registry is specific to the layer, and is used to house the components
registered at the layer level. The second registry is set up and torn down for
each test, allowing tests to register their own components freely.

First, we'll create a simple dummy utility to illustrate registrations.

>>> from zope.interface import Interface, implements

>>> class IDummyUtility(Interface):
... pass
>>> class DummyUtility(object):
... implements(IDummyUtility)
... def __init__(self, name):
... self.name = name
... def __repr__(self):
... return "<DummyUtility %s>" % self.name

The two key methods are:

* ``zca.pushGlobalRegistry()``, which creates a new global registry.
* ``zca.popGlobalRegistry()``, which restores the previous global registry.

**Warning:** You *must* balance your calls to these methods. If you call
``pushGlobalRegistry()`` in ``setUp()``, call ``popGlobalRegistry()`` in
``tearDown()``. Ditto for ``testSetUp()`` and ``testTearDown()``.

Let's now create our layer.

>>> from zope.component import provideUtility
>>> from plone.testing import Layer
>>> from plone.testing import zca

>>> class ComponentSandbox(Layer):
... def setUp(self):
... zca.pushGlobalRegistry()
... provideUtility(DummyUtility("layer"), name="layer")
... def tearDown(self):
... zca.popGlobalRegistry()
... def testSetUp(self):
... zca.pushGlobalRegistry()
... def testTearDown(self):
... zca.popGlobalRegistry()
>>> COMPONENT_SANDBOX = ComponentSandbox()

Let's now simulate a test using this layer.

To begin with, we have the default registry.

>>> from zope.component import getGlobalSiteManager, getSiteManager
>>> getSiteManager() is getGlobalSiteManager()
True

>>> defaultGlobalSiteManager = getGlobalSiteManager()

>>> from zope.component import queryUtility
>>> queryUtility(IDummyUtility, name="layer") is None
True

We'll now simulate layer setup. This will push a new registry onto the stack:

>>> COMPONENT_SANDBOX.setUp()

>>> getSiteManager() is getGlobalSiteManager()
True
>>> getGlobalSiteManager() is defaultGlobalSiteManager
False
>>> layerGlobalSiteManager = getGlobalSiteManager()

>>> queryUtility(IDummyUtility, name="layer")
<DummyUtility layer>

We'll then simulate a test that registers a global component:

>>> COMPONENT_SANDBOX.testSetUp()

>>> getSiteManager() is getGlobalSiteManager()
True
>>> getGlobalSiteManager() is defaultGlobalSiteManager
False
>>> getGlobalSiteManager() is layerGlobalSiteManager
False

Our previously registered component is still here.

>>> queryUtility(IDummyUtility, name="layer")
<DummyUtility layer>

We can also register a new one.

>>> provideUtility(DummyUtility("test"), name="test")
>>> queryUtility(IDummyUtility, name="layer")
<DummyUtility layer>
>>> queryUtility(IDummyUtility, name="test")
<DummyUtility test>

On test tear-down, only the second utility disappears:

>>> COMPONENT_SANDBOX.testTearDown()

>>> getSiteManager() is getGlobalSiteManager()
True
>>> getGlobalSiteManager() is defaultGlobalSiteManager
False
>>> getGlobalSiteManager() is layerGlobalSiteManager
True

>>> queryUtility(IDummyUtility, name="layer")
<DummyUtility layer>
>>> queryUtility(IDummyUtility, name="test") is None
True

If we tear down the layer too, we're back where we started:

>>> COMPONENT_SANDBOX.tearDown()

>>> getSiteManager() is getGlobalSiteManager()
True
>>> getGlobalSiteManager() is defaultGlobalSiteManager
True

>>> queryUtility(IDummyUtility, name="layer") is None
True
>>> queryUtility(IDummyUtility, name="test") is None
True

Loading ZCML with registry sandboxing
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

One of the frequent use cases is a layer that loads a set of ZCML
files and sandbox the resulting registry.

We provide two key methods to cover that use case:

* ``zca.setUpZcmlFiles()``, which loads a set of ZCML files by the mean of a
new configuration context into a new global registry.
* ``zca.tearDownZcmlFiles()``, which restores the previous configuration
context and the previous global registry.

>>> from plone.testing import Layer
>>> from plone.testing import zca
>>> import plone.testing

>>> class ZCMLSandbox(Layer):
... def setUp(self):
... zca.setUpZcmlFiles((
... ('testing_zca.zcml', plone.testing),
... ))
... def tearDown(self):
... zca.tearDownZcmlFiles()
>>> ZCML_SANDBOX = ZCMLSandbox()

>>> class MoreSpecificZCMLSandbox(Layer):
... def setUp(self):
... zca.setUpZcmlFiles((
... ('testing_zca_more_specific.zcml', plone.testing),
... ))
... def tearDown(self):
... zca.tearDownZcmlFiles()
>>> MORE_SPECIFIC_ZCML_SANDBOX = MoreSpecificZCMLSandbox()

Before layer setup, the utility is not registered.

>>> queryUtility(Interface, name="layer")

We'll now simulate layer setup. This will push a new registry onto the stack:

>>> ZCML_SANDBOX.setUp()

>>> getSiteManager() is getGlobalSiteManager()
True
>>> getGlobalSiteManager() is defaultGlobalSiteManager
False
>>> queryUtility(Interface, name="layer")
<Dummy utility>

Before layer setup, a second utility is not registered.

>>> queryUtility(Interface, name="more_specific_layer")

We'll now simulate the setup of the more specific layer.

>>> MORE_SPECIFIC_ZCML_SANDBOX.setUp()
>>> queryUtility(Interface, name="more_specific_layer")
<Dummy utility>
>>> MORE_SPECIFIC_ZCML_SANDBOX.tearDown()

After layer teardown, the utility is not registered anymore.

>>> queryUtility(Interface, name="more_specific_layer")

>>> ZCML_SANDBOX.tearDown()

After layer teardown, the utility is not registered anymore.

>>> queryUtility(Interface, name="layer")


We make similar set of checks for a second layer at the same level
as the original ZCML_SANDBOX

>>> ZCML_SANDBOX_SAME_LEVEL = ZCMLSandbox()

>>> ZCML_SANDBOX_SAME_LEVEL.setUp()

>>> getSiteManager() is getGlobalSiteManager()
True
>>> getGlobalSiteManager() is defaultGlobalSiteManager
False
>>> queryUtility(Interface, name="layer")
<Dummy utility>

>>> ZCML_SANDBOX_SAME_LEVEL.tearDown()

``zca.tearDownZcmlFiles`` checks if it is sync with ``zca.setUpZcmlFiles``.

>>> zca.tearDownZcmlFiles()
Traceback (most recent call last):
...
OutOfSyncError: tearDownZcmlFiles() called out of sync with setUpZcmlFiles()


Security
--------

The Zope Security layers are found in the module ``plone.testing.security``:

>>> from plone.testing import security

For testing, we need a testrunner

>>> from zope.testing.testrunner import runner

Layers
~~~~~~

The ``security.CHECKERS`` layer makes sure that ``zope.security`` checkers are
correctly set up and torn down.

>>> "%s.%s" % (security.CHECKERS.__module__, security.CHECKERS.__name__,)
'plone.testing.security.Checkers'

>>> security.CHECKERS.__bases__
()

Before the test, our custom checker is not in the registry.

>>> class DummyObject(object):
... pass

>>> from zope.security.interfaces import IChecker
>>> from zope.interface import implements
>>> class FauxChecker(object):
... implements(IChecker)
... # we should really implement the interface here, but oh well

>>> from zope.security.checker import getCheckerForInstancesOf
>>> getCheckerForInstancesOf(DummyObject) is None
True

Layer setup stacks the current checkers.

>>> options = runner.get_options([], [])
>>> setupLayers = {}
>>> runner.setup_layer(options, security.CHECKERS, setupLayers)
Set up plone.testing.security.Checkers in ... seconds.

We can now set up a checker. In real life, this may happen during ZCML
configuration, but here will just call the API directlyMost likely, we'd do
this in a child layer:

>>> from zope.security.checker import defineChecker
>>> fauxChecker = FauxChecker()
>>> defineChecker(DummyObject, fauxChecker)

>>> getCheckerForInstancesOf(DummyObject) is fauxChecker
True

Let's now simulate a test that may use the checker.

>>> security.CHECKERS.testSetUp()
>>> getCheckerForInstancesOf(DummyObject) is fauxChecker
True
>>> security.CHECKERS.testTearDown()

We still have the checker after test tear-down:

>>> getCheckerForInstancesOf(DummyObject) is fauxChecker
True

However, when we tear down the layer, the checker is gone:

>>> runner.tear_down_unneeded(options, [], setupLayers)
Tear down plone.testing.security.Checkers in ... seconds.

>>> getCheckerForInstancesOf(DummyObject) is None
True


Zope Publisher layers
---------------------

The Zope Publisher layers are found in the module ``plone.testing.publisher``:

>>> from plone.testing import publisher

For testing, we need a testrunner

>>> from zope.testing.testrunner import runner

ZCML directives
~~~~~~~~~~~~~~~

The ``publisher.PUBLISHER_DIRECTIVES`` layer extends the
``zca.ZCML_DIRECTIVES`` layer to extend its ZCML configuration context with
the ``zope.app.publisher`` and ``zope.security`` directives available. It
also extends ``security.CHECKERS``.

>>> from plone.testing import zca, security

>>> "%s.%s" % (publisher.PUBLISHER_DIRECTIVES.__module__, publisher.PUBLISHER_DIRECTIVES.__name__,)
'plone.testing.publisher.PublisherDirectives'

>>> publisher.PUBLISHER_DIRECTIVES.__bases__
(<Layer 'plone.testing.zca.ZCMLDirectives'>, <Layer 'plone.testing.security.Checkers'>)

Before the test, we cannot use e.g. the ``<permission />`` or
``<browser:view />`` directives without loading the necessary ``meta.zcml``
files.

>>> from zope.configuration import xmlconfig
>>> xmlconfig.string("""\
... <configure package="plone.testing"
... xmlns="http://namespaces.zope.org/zope"
... xmlns:browser="http://namespaces.zope.org/browser"
... i18n_domain="plone.testing.tests">
... <permission id="plone.testing.Test" title="plone.testing: Test" />
... <browser:view
... for="*"
... name="plone.testing-test"
... class="plone.testing.tests.DummyView"
... permission="zope.Public"
... />
... </configure>""")
Traceback (most recent call last):
...
ZopeXMLConfigurationError: File "<string>", line 5.4
ConfigurationError: ('Unknown directive', u'http://namespaces.zope.org/zope', u'permission')

Layer setup creates a configuration context we can use to load further
configuration.

>>> options = runner.get_options([], [])
>>> setupLayers = {}
>>> runner.setup_layer(options, publisher.PUBLISHER_DIRECTIVES, setupLayers)
Set up plone.testing.zca.LayerCleanup in ... seconds.
Set up plone.testing.zca.ZCMLDirectives in ... seconds.
Set up plone.testing.security.Checkers in ... seconds.
Set up plone.testing.publisher.PublisherDirectives in ... seconds.


Let's now simulate a test that uses this configuration context to load the
same ZCML string.

>>> zca.ZCML_DIRECTIVES.testSetUp()
>>> security.CHECKERS.testSetUp()
>>> publisher.PUBLISHER_DIRECTIVES.testSetUp()

>>> context = zca.ZCML_DIRECTIVES['configurationContext'] # would normally be self.layer['configurationContext']
>>> xmlconfig.string("""\
... <configure package="plone.testing"
... xmlns="http://namespaces.zope.org/zope"
... xmlns:browser="http://namespaces.zope.org/browser"
... i18n_domain="plone.testing.tests">
... <permission id="plone.testing.Test" title="plone.testing: Test" />
... <browser:view
... for="*"
... name="plone.testing-test"
... class="plone.testing.tests.DummyView"
... permission="zope.Public"
... />
... </configure>""", context=context) is context
True

The permission and view are now registered:

>>> from zope.component import queryUtility
>>> from zope.security.interfaces import IPermission

>>> queryUtility(IPermission, name=u"plone.testing.Test")
<zope.security.permission.Permission object at ...>

>>> from zope.interface import Interface
>>> from zope.publisher.interfaces.browser import IDefaultBrowserLayer
>>> from zope.component import getSiteManager
>>> siteManager = getSiteManager()

>>> [x.factory for x in siteManager.registeredAdapters()
... if x.provided==Interface and x.required==(Interface, IDefaultBrowserLayer)
... and x.name==u"plone.testing-test"]
[<class 'zope.app.publisher.browser.viewmeta.plone.testing-test'>]

We can then simulate test tear-down:

>>> publisher.PUBLISHER_DIRECTIVES.testTearDown()
>>> security.CHECKERS.testTearDown()
>>> zca.ZCML_DIRECTIVES.testTearDown()

Note that you'd normally combine this layer with the ``zca.UNIT_TESTING`` or a
similar layer to automatically tear down the component architecture between
each test. Here, we need to do it manually.

>>> from zope.component.testing import tearDown
>>> tearDown()

Layer tear-down does nothing.

>>> runner.tear_down_unneeded(options, [], setupLayers)
Tear down plone.testing.publisher.PublisherDirectives in ... seconds.
Tear down plone.testing.zca.ZCMLDirectives in ... seconds.
Tear down plone.testing.zca.LayerCleanup in ... seconds.
Tear down plone.testing.security.Checkers in ... seconds.

>>> zca.ZCML_DIRECTIVES.get('configurationContext', None) is None
True


Zope Object Database layers
---------------------------

The ZODB layers are found in the module ``plone.testing.zodb``:

>>> from plone.testing import zodb

For testing, we need a testrunner

>>> from zope.testing.testrunner import runner

Empty ZODB layer
~~~~~~~~~~~~~~~~

The ``EMPTY_ZODB`` layer is used to set up an empty ZODB using
``DemoStorage``.

The storage and database are set up as layer fixtures. The database is exposed
as the resource ``zodbDB``.

A connection is opened for each test and exposed as ``zodbConnection``. The
ZODB root is also exposed, as ``zodbRoot``. A new transaction is begun for
each test. On test tear-down, the transaction is aborted, the connection is
closed, and the two test-specific resources are deleted.

The layer has no bases.

>>> "%s.%s" % (zodb.EMPTY_ZODB.__module__, zodb.EMPTY_ZODB.__name__,)
'plone.testing.zodb.EmptyZODB'

>>> zodb.EMPTY_ZODB.__bases__
()

Layer setup creates the database, but not a connection.

>>> options = runner.get_options([], [])
>>> setupLayers = {}
>>> runner.setup_layer(options, zodb.EMPTY_ZODB, setupLayers)
Set up plone.testing.zodb.EmptyZODB in ... seconds.

>>> db = zodb.EMPTY_ZODB['zodbDB']
>>> db.storage
EmptyZODB

>>> zodb.EMPTY_ZODB.get('zodbConnection', None) is None
True
>>> zodb.EMPTY_ZODB.get('zodbRoot', None) is None
True

Let's now simulate a test.

>>> zodb.EMPTY_ZODB.testSetUp()

The test would then execute. It may use the ZODB root.

>>> zodb.EMPTY_ZODB['zodbConnection']
<Connection at ...>

>>> zodb.EMPTY_ZODB['zodbRoot']
{}

>>> zodb.EMPTY_ZODB['zodbRoot']['foo'] = 'bar'

On test tear-down, the transaction is aborted and the connection is closed.

>>> zodb.EMPTY_ZODB.testTearDown()

>>> zodb.EMPTY_ZODB.get('zodbConnection', None) is None
True

>>> zodb.EMPTY_ZODB.get('zodbRoot', None) is None
True

The transaction has been rolled back.

>>> conn = zodb.EMPTY_ZODB['zodbDB'].open()
>>> conn.root()
{}
>>> conn.close()

Layer tear-down closes and deletes the database.

>>> runner.tear_down_unneeded(options, [], setupLayers)
Tear down plone.testing.zodb.EmptyZODB in ... seconds.

>>> zodb.EMPTY_ZODB.get('zodbDB', None) is None
True

Extending the ZODB layer
~~~~~~~~~~~~~~~~~~~~~~~~

When creating a test fixture, it is often desirable to add some initial data
to the database. If you want to do that once on layer setup, you can create
your own layer class based on ``EmptyZODB`` and override its
``createStorage()`` and/or ``createDatabase()`` methods to return a
pre-populated database.


>>> import transaction
>>> from ZODB.DemoStorage import DemoStorage
>>> from ZODB.DB import DB

>>> class PopulatedZODB(zodb.EmptyZODB):
...
... def createStorage(self):
... return DemoStorage("My storage")
...
... def createDatabase(self, storage):
... db = DB(storage)
... conn = db.open()
...
... conn.root()['someData'] = 'a string'
...
... transaction.commit()
... conn.close()
...
... return db

>>> POPULATED_ZODB = PopulatedZODB()

We'll use this new layer in a similar manner to the test above, showing that
the data is there for each test, but that other changes are rolled back.

>>> options = runner.get_options([], [])
>>> setupLayers = {}
>>> runner.setup_layer(options, POPULATED_ZODB, setupLayers)
Set up PopulatedZODB in ... seconds.

>>> db = POPULATED_ZODB['zodbDB']
>>> db.storage
My storage

>>> POPULATED_ZODB.get('zodbConnection', None) is None
True
>>> POPULATED_ZODB.get('zodbRoot', None) is None
True

Let's now simulate a test.

>>> POPULATED_ZODB.testSetUp()

The test would then execute. It may use the ZODB root.

>>> POPULATED_ZODB['zodbConnection']
<Connection at ...>

>>> POPULATED_ZODB['zodbRoot']
{'someData': 'a string'}

>>> POPULATED_ZODB['zodbRoot']['foo'] = 'bar'

On test tear-down, the transaction is aborted and the connection is closed.

>>> POPULATED_ZODB.testTearDown()

>>> POPULATED_ZODB.get('zodbConnection', None) is None
True

>>> POPULATED_ZODB.get('zodbRoot', None) is None
True

The transaction has been rolled back.

>>> conn = POPULATED_ZODB['zodbDB'].open()
>>> conn.root()
{'someData': 'a string'}
>>> conn.close()

Layer tear-down closes and deletes the database.

>>> runner.tear_down_unneeded(options, [], setupLayers)
Tear down PopulatedZODB in ... seconds.

>>> POPULATED_ZODB.get('zodbDB', None) is None
True

Stacking ``DemoStorage`` storages
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The example above shows how to create a simple test fixture with a custom
database. It is sometimes useful to be able to stack these fixtures, so that
a base layer sets up some data for one set of tests, and a child layer
extends this, temporarily, with more data.

This can be achieved using layer bases and resource shadowing, combined with
ZODB's stackable DemoStorage. There is even a helper function available:

>>> from plone.testing import Layer
>>> from plone.testing import zodb
>>> import transaction

>>> class ExpandedZODB(Layer):
... defaultBases = (POPULATED_ZODB,)
...
... def setUp(self):
... # Get the database from the base layer
...
... self['zodbDB'] = db = zodb.stackDemoStorage(self.get('zodbDB'), name='ExpandedZODB')
...
... conn = db.open()
... conn.root()['additionalData'] = "Some new data"
... transaction.commit()
... conn.close()
...
... def tearDown(self):
... # Close the database and delete the shadowed copy
...
... self['zodbDB'].close()
... del self['zodbDB']

>>> EXPANDED_ZODB = ExpandedZODB()

Notice that we are using plain ``Layer`` as a base class here. We obtain the
underlying database from our bases using the resource manager, and then
create a shadow copy using a stacked storage. Stacked storages contain the
data of the original storage, but save changes in a separate (and, in this
case, temporary) storage.

Let's simulate a test run again to show how this would work.

>>> options = runner.get_options([], [])
>>> setupLayers = {}
>>> runner.setup_layer(options, EXPANDED_ZODB, setupLayers)
Set up PopulatedZODB in ... seconds.
Set up ExpandedZODB in ... seconds.

>>> db = EXPANDED_ZODB['zodbDB']
>>> db.storage
ExpandedZODB

>>> EXPANDED_ZODB.get('zodbConnection', None) is None
True
>>> EXPANDED_ZODB.get('zodbRoot', None) is None
True

Let's now simulate a test.

>>> POPULATED_ZODB.testSetUp()
>>> EXPANDED_ZODB.testSetUp()

The test would then execute. It may use the ZODB root.

>>> EXPANDED_ZODB['zodbConnection']
<Connection at ...>

>>> EXPANDED_ZODB['zodbRoot'] == dict(someData='a string', additionalData='Some new data')
True

>>> POPULATED_ZODB['zodbRoot']['foo'] = 'bar'

On test tear-down, the transaction is aborted and the connection is closed.

>>> EXPANDED_ZODB.testTearDown()
>>> POPULATED_ZODB.testTearDown()

>>> EXPANDED_ZODB.get('zodbConnection', None) is None
True

>>> EXPANDED_ZODB.get('zodbRoot', None) is None
True

The transaction has been rolled back.

>>> conn = EXPANDED_ZODB['zodbDB'].open()
>>> conn.root() == dict(someData='a string', additionalData='Some new data')
True
>>> conn.close()

We'll now tear down the expanded layer and inspect the database again.

>>> runner.tear_down_unneeded(options, [POPULATED_ZODB], setupLayers)
Tear down ExpandedZODB in ... seconds.

>>> conn = EXPANDED_ZODB['zodbDB'].open()
>>> conn.root()
{'someData': 'a string'}

>>> conn.close()

Finally, we'll tear down the rest of the layers.

>>> runner.tear_down_unneeded(options, [], setupLayers)
Tear down PopulatedZODB in ... seconds.

>>> EXPANDED_ZODB.get('zodbDB', None) is None
True
>>> POPULATED_ZODB.get('zodbDB', None) is None
True