Test plugins evaluate template expressions and return True or False. With test plugins you can create :ref:`conditionals <playbooks_conditionals>` to implement the logic of your tasks, blocks, plays, playbooks, and roles. Ansible uses the `standard tests `_ shipped as part of Jinja, and adds some specialized test plugins. You can :ref:`create custom Ansible test plugins <developing_test_plugins>`.
You can add a custom test plugin by dropping it into a ``test_plugins`` directory adjacent to your play, inside a role, or by putting it in one of the test plugin directory sources configured in :ref:`ansible.cfg <ansible_configuration_settings>`.
You can use tests anywhere you can use templating in Ansible: in a play, in variables file, or in a Jinja2 template for the :ref:`template <template_module>` module. For more information on using test plugins, see :ref:`playbooks_tests`.
Tests always return ``True`` or ``False``, they are always a boolean, if you need a different return type, you should be looking at filters.
You can recognize test plugins by the use of the ``is`` statement in a template, they can also be used as part of the ``select`` family of filters.
..code-block:: YAML+Jinja
vars:
is_ready: '{{ task_result is success }}'
tasks:
- name: conditionals are always in 'template' context
action: dostuff
when: task_result is failed
Tests will always have an ``_input`` and this is normally what is on the left side of ``is``. Tests can also take additional parameters as you would to most programming functions. These parameters can be either ``positional`` (passed in order) or ``named`` (passed as key=value pairs). When passing both types, positional arguments should go first.
..code-block:: YAML+Jinja
tasks:
- name: pass positional parameter to match test
action: dostuff
when: myurl is match("https://example.com/users/.*/resources")
- name: pass named parameter to truthy test
action: dostuff
when: myvariable is truthy(convert_bool=True)
- name: pass both types to 'version' test
action: dostuff
when: sample_semver_var is version('2.0.0-rc.1+build.123', 'lt', version_type='semver')
Using test plugins with lists
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
As mentioned above, one way to use tests is with the ``select`` familiy of filters (``select``, ``reject``, ``selectattr``, ``rejectattr``).
..code-block:: YAML+Jinja
# give me only defined variables from a list of variables, using 'defined' test
good_vars: "{{ all_vars|select('defined') }}"
# this uses the 'equalto' test to filter out non 'fixed' type of addresses from a list
You can use ``ansible-doc -t filter -l`` to see the list of available plugins. Use ``ansible-doc -t filter <plugin name>`` to see specific documents and examples.
