Add Atoum tests documentation (#109)

* Add Atoum tests documentation

* Apply suggestions + how to run

source/plugins/index.rst

@@ -25,3 +25,4 @@ If you want to see more advanced examples of what it is possible to do with plug
    massiveactions
    tips
    notifications
+   test

source/plugins/test.rst

@@ -0,0 +1,74 @@
+Unit Testing
+-----------------
+
+Goals
+^^^^^
+
+As a plugin's complexity increases so does the possibility of a feature or bug fix breaking some other part of the plugin. For this, it is recommended that plugins have some unit tests in place to detect when expected functionality breaks.
+
+Bootstrap
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Next, you need to create a bootstrap file to prepare the testing environment. This file should be located at ``tests/bootstrap.php``.
+In the bootstrap file, you need to import a few required files and set a few constants, as well as loading your plugin. Note that you must manually cheeck prerequisites since this check is not called automatically.
+For example:
+
+.. code-block:: php
+
+    <?php
+    global $CFG_GLPI;
+
+    define('GLPI_ROOT', dirname(dirname(dirname(__DIR__))));
+    define("GLPI_CONFIG_DIR", GLPI_ROOT . "/tests");
+
+    include GLPI_ROOT . "/inc/includes.php";
+    include_once GLPI_ROOT . '/tests/GLPITestCase.php';
+    include_once GLPI_ROOT . '/tests/DbTestCase.php';
+
+    $plugin = new \Plugin();
+    $plugin->checkStates(true);
+    $plugin->getFromDBbyDir('myplugin');
+
+    if (!plugin_myplugin_check_prerequisites()) {
+        echo "\nPrerequisites are not met!";
+        die(1);
+    }
+
+    if (!$plugin->isInstalled('myplugin')) {
+        $plugin->install($plugin->getID());
+    }
+    if (!$plugin->isActivated('myplugin')) {
+        $plugin->activate($plugin->getID());
+    }
+
+You must replace "myplugin" with the directory name of your plugin.
+
+Unit test files
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+All unit tests must be placed inside the ``tests/units`` directory in your plugin.
+Each test file has to correspond to an existing class name. If your plugin has a file ``inc/test.class.php`` with the class name ``PluginMypluginTest``, the test file must be named ``PluginMypluginTest.php``.
+
+Running your tests
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+To run your tests, go to the root of your GLPI installation and run:
+
+.. code-block:: bash
+
+    vendor/bin/atoum -bf plugins/myplugin/tests/bootstrap.php -d plugins/myplugin/tests/
+
+You must replace "myplugin" with the directory name of your plugin.
+
+Real examples
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The following plugins are a good example of how to implement Atoum tests:
+
+- `JAMF Plugin for GLPI <https://github.com/cconard96/jamf>`_
+- `Fields Plugin for GLPI <https://github.com/pluginsGLPI/fields>`_
+
+Further reading
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The `Atoum documentation <https://atoum.readthedocs.io/>`_ is a good place to start if you are not familiar with unit testing or Atoum.