Added tests for Clear Cache Command. (#11066)

* Added tests for Clear Cache Command.

* Fix side-effects breaking other tests

Co-authored-by: Jordi Boggiano <j.boggiano@seld.be>

tests/Composer/Test/Command/ClearCacheCommandTest.php

@@ -0,0 +1,61 @@
+<?php declare(strict_types=1);
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Test\Command;
+
+use Composer\Test\TestCase;
+use Composer\Util\Platform;
+
+class ClearCacheCommandTest extends TestCase
+{
+    public function tearDown(): void
+    {
+        // --no-cache triggers the env to change so make sure the env is cleaned up after these tests run
+        Platform::clearEnv('COMPOSER_CACHE_DIR');
+    }
+
+    public function testClearCacheCommandSuccess(): void
+    {
+        $appTester = $this->getApplicationTester();
+        $appTester->run(['command' => 'clear-cache']);
+
+        $appTester->assertCommandIsSuccessful();
+
+        $output = $appTester->getDisplay(true);
+
+        $this->assertStringContainsString('All caches cleared.', $output);
+    }
+
+    public function testClearCacheCommandWithOptionGarbageCollection(): void
+    {
+        $appTester = $this->getApplicationTester();
+        $appTester->run(['command' => 'clear-cache', '--gc' => true]);
+
+        $appTester->assertCommandIsSuccessful();
+
+        $output = $appTester->getDisplay(true);
+
+        $this->assertStringContainsString('All caches garbage-collected.', $output);
+    }
+
+    public function testClearCacheCommandWithOptionNoCache(): void
+    {
+        $appTester = $this->getApplicationTester();
+        $appTester->run(['command' => 'clear-cache', '--no-cache' => true]);
+
+        $appTester->assertCommandIsSuccessful();
+
+        $output = $appTester->getDisplay(true);
+
+        $this->assertStringContainsString('Cache is not enabled', $output);
+    }
+}