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

docs/5.x/tests-system.md

@@ -195,6 +195,45 @@ 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 `5.1.0`, you can now easily check if your plugin is using any core dependencies by running the `tests:check-direct-dependency-use` command. With the release of Matomo 5, plugins should not use core dependencies directly but instead use them via [proxies](https://developer.matomo.org/guides/migrate-matomo-4-to-5#vendor-proxies). To have a check for this in your test suite and run it automatically, you can also write a system test case by using the sample code below:
+
+```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, '5.1.0', '<=') || !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}';
+
+        $checkDirectDependencyUse = new CheckDirectDependencyUse();
+        $console = new \Piwik\Console(self::$fixture->piwikEnvironment);
+        $console->addCommands([$checkDirectDependencyUse]);
+
+        $command = $console->find('tests:check-direct-dependency-use');
+        $arguments = [
+            '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`.