diff --git a/tests/unit/TestCase.php b/tests/unit/TestCase.php
index d098f30..9a65138 100644
--- a/tests/unit/TestCase.php
+++ b/tests/unit/TestCase.php
@@ -6,6 +6,21 @@ class TestCase extends \yii\test\TestCase
 {
 	public static $params;
 
+	protected function setUp() {
+		parent::setUp();
+	}
+
+	protected function tearDown()
+	{
+		parent::tearDown();
+		// If defined and set to true, destroy the app after each test.
+		// This will cause tests to fail, that rely on an existing app, but don't
+		// call requireApp() in their setUp().
+		if (defined('YII_DESTROY_APP_ON_TEARDOWN') && YII_DESTROY_APP_ON_TEARDOWN === true) {
+			$this->destroyApp();
+		}
+	}
+	
 	public function getParam($name)
 	{
 		if (self::$params === null) {
@@ -32,4 +47,9 @@ class TestCase extends \yii\test\TestCase
 			$usedConfig = $newConfig;
 		}
 	}
+	
+	protected function destroyApp()
+	{
+		\yii::$app = null;
+	}
 }
diff --git a/tests/unit/bootstrap.php b/tests/unit/bootstrap.php
index 285b55b..55f8158 100644
--- a/tests/unit/bootstrap.php
+++ b/tests/unit/bootstrap.php
@@ -2,6 +2,7 @@
 
 define('YII_ENABLE_ERROR_HANDLER', false);
 define('YII_DEBUG', true);
+define('YII_DESTROY_APP_ON_TEARDOWN', false);
 $_SERVER['SCRIPT_NAME'] = '/' . __DIR__;
 $_SERVER['SCRIPT_FILENAME'] = __FILE__;
 
@@ -9,6 +10,4 @@ require_once(__DIR__ . '/../../yii/Yii.php');
 
 Yii::setAlias('@yiiunit', __DIR__);
 
-new \yii\web\Application(array('id' => 'testapp', 'basePath' => __DIR__));
-
 require_once(__DIR__ . '/TestCase.php');