Added documentation for tests:check-direct-dependency-use command, #PG-3272

docs/5.x/tests-system.md

@@ -195,6 +195,44 @@ class ApiTest extends SystemTestCase
 }
 ```
 
+## How to write a test to scan for Matomo core dependencies being used directly in your plugins
+
+With the release of Matomo `v5.1.0`, you can now check the usage of core dependencies in your plugin directly using the `tests:check-direct-dependency-use` command. With the release of Matomo 5, plugins should not use core dependencies directly but instead [prefix](https://developer.matomo.org/guides/migrate-matomo-4-to-5#vendor-proxies) them. You can also write a system test case to test the same by using the sample code below
+
+```php
+<?php
+
+use Piwik\Plugins\TestRunner\Commands\CheckDirectDependencyUse;
+use Piwik\Tests\Framework\TestCase\SystemTestCase;
+use Piwik\Version;
+use Symfony\Component\Console\Input\ArrayInput;
+use Symfony\Component\Console\Output\NullOutput;
+
+class CheckDirectDependencyUseCommandTest extends SystemTestCase
+{
+    public function testCommand()
+    {
+        if (version_compare(Version::VERSION, '5.0.2', '<=') && !\Piwik\file_exists(PIWIK_INCLUDE_PATH . '/plugins/TestRunner/Commands/CheckDirectDependencyUse.php')) {
+            $this->markTestSkipped('tests:check-direct-dependency-use is not available in this version');
+        }
+        $pluginName = '{YOUR_PLUGIN_NAME}';
+        $console = new \Piwik\Console(self::$fixture->piwikEnvironment);
+        $checkDirectDependencyUse = new CheckDirectDependencyUse();
+        $console->addCommands([$checkDirectDependencyUse]);
+        $command = $console->find('tests:check-direct-dependency-use');
+        $arguments = array(
+            'command'    => 'tests:check-direct-dependency-use',
+            '--plugin' => $pluginName,
+            '--grep-vendor'
+        );
+        $inputObject = new ArrayInput($arguments);
+        $command->run($inputObject, new NullOutput());
+
+        $this->assertEmpty($checkDirectDependencyUse->usesFoundList[$pluginName]);
+    }
+}
+```
+
 ## Writing tests for commands
 
 It is also possible to write system tests for console commands. These tests should extend `Piwik\Tests\Framework\TestCase\ConsoleCommandTestCase`.