Testing with zope.component#
zope.component is a fantastic aspect-oriented library for Python,
however its unit testing support is somewhat convoluted. If you need
to test code that registers adapters, utilities and the like then you
may need to provide a sterile component registry. For historical
reasons, component registries are known as Site Managers in
zope.component
.
Testfixtures provides the TestComponents
helper
which provides just such a sterile registry. It should be instantiated
in your TestCase
’s setUp()
method. It’s
components.TestComponents.uninstall()
method should be called in the test’s
tearDown()
method.
Normally, :any :zope.component.getSiteManager returns whatever
the current registry is. This may be influenced by frameworks that use
zope.component
which can means that unit tests have no
baseline to start with:
>>> from zope.component import getSiteManager
>>> original = getSiteManager()
>>> print(original)
<BaseGlobalComponents base>
Once we’ve got a TestComponents
in place, we know what
we’re getting:
>>> from testfixtures.components import TestComponents
>>> components = TestComponents()
>>> getSiteManager()
<Components Testing>
The registry that zope.component.getSiteManager
returns is now also
available as an attribute of the TestComponents
instance:
>>> getSiteManager() is components.registry
True
It’s also empty:
>>> tuple(components.registry.registeredUtilities())
()
>>> tuple(components.registry.registeredAdapters())
()
>>> tuple(components.registry.registeredHandlers())
()
You can do whatever you like with this registry. When you’re done,
just call the components.TestComponents.uninstall()
method:
>>> components.uninstall()
Now you’ll have the original registy back in place:
>>> getSiteManager() is original
True