diff --git a/tests/unit/TestCase.php b/tests/unit/TestCase.php
index 314e2b0..fbc0da7 100644
--- a/tests/unit/TestCase.php
+++ b/tests/unit/TestCase.php
@@ -13,12 +13,7 @@ class TestCase extends \yii\test\TestCase
 	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();
-		}
+		$this->destroyApp();
 	}
 	
 	public function getParam($name,$default=null)
@@ -29,28 +24,19 @@ class TestCase extends \yii\test\TestCase
 		return isset(self::$params[$name]) ? self::$params[$name] : $default;
 	}
 	
-	protected function requireApp($requiredConfig=array())
+	protected function mockApplication($requiredConfig=array())
 	{
-		static $usedConfig = array();
 		static $defaultConfig = array(
 			'id' => 'testapp',
 			'basePath' => __DIR__,
 		);
 		
-		$newConfig = array_merge( $defaultConfig, $requiredConfig );
 		$appClass = $this->getParam( 'appClass', '\yii\web\Application' );
-		
-		if (!(\yii::$app instanceof $appClass)) {
-			new $appClass( $newConfig );
-			$usedConfig = $newConfig;
-		} elseif ($newConfig !== $usedConfig) {
-			new $appClass( $newConfig );
-			$usedConfig = $newConfig;
-		}
+		new $appClass(array_merge($defaultConfig,$requiredConfig));
 	}
 	
 	protected function destroyApp()
 	{
-		\yii::$app = null;
+		\Yii::$app = null;
 	}
 }
diff --git a/tests/unit/bootstrap.php b/tests/unit/bootstrap.php
index 55f8158..a0fdab4 100644
--- a/tests/unit/bootstrap.php
+++ b/tests/unit/bootstrap.php
@@ -2,7 +2,6 @@
 
 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__;
 
diff --git a/tests/unit/framework/caching/CacheTest.php b/tests/unit/framework/caching/CacheTest.php
index f3eda7a..a17f126 100644
--- a/tests/unit/framework/caching/CacheTest.php
+++ b/tests/unit/framework/caching/CacheTest.php
@@ -16,7 +16,7 @@ abstract class CacheTest extends TestCase
 	protected function setUp()
 	{
 		parent::setUp();
-		$this->requireApp();
+		$this->mockApplication();
 	}
 	
 	public function testSet()
diff --git a/tests/unit/framework/helpers/HtmlTest.php b/tests/unit/framework/helpers/HtmlTest.php
index 9ba6b43..294cae0 100644
--- a/tests/unit/framework/helpers/HtmlTest.php
+++ b/tests/unit/framework/helpers/HtmlTest.php
@@ -10,7 +10,7 @@ class HtmlTest extends TestCase
 {
 	public function setUp()
 	{
-		$this->requireApp(array(
+		$this->mockApplication(array(
 			'components' => array(
 				'request' => array(
 					'class' => 'yii\web\Request',