diff --git a/framework/caching/DbCache.php b/framework/caching/DbCache.php
index 75f13b0..b74c5e0 100644
--- a/framework/caching/DbCache.php
+++ b/framework/caching/DbCache.php
@@ -104,7 +104,7 @@ class DbCache extends Cache
 		$query = new Query;
 		$query->select(array('data'))
 			->from($this->cacheTableName)
-			->where('id = :id AND (expire = 0 OR expire > :time)', array(':id' => $key, ':time' => time()));
+			->where('id = :id AND (expire = 0 OR expire >' . time() . ')', array(':id' => $key));
 		$db = $this->getDb();
 		if ($db->enableQueryCache) {
 			// temporarily disable and re-enable query caching
@@ -131,7 +131,7 @@ class DbCache extends Cache
 		$query->select(array('id', 'data'))
 			->from($this->cacheTableName)
 			->where(array('id' => $keys))
-			->andWhere("expire = 0 OR expire > " . time() . ")");
+			->andWhere('(expire = 0 OR expire > ' . time() . ')');
 
 		$db = $this->getDb();
 		if ($db->enableQueryCache) {
diff --git a/tests/unit/.gitignore b/tests/unit/.gitignore
new file mode 100644
index 0000000..34651d7
--- /dev/null
+++ b/tests/unit/.gitignore
@@ -0,0 +1 @@
+runtime/cache/*
\ No newline at end of file
diff --git a/tests/unit/framework/caching/ApcCacheTest.php b/tests/unit/framework/caching/ApcCacheTest.php
new file mode 100644
index 0000000..74ede2a
--- /dev/null
+++ b/tests/unit/framework/caching/ApcCacheTest.php
@@ -0,0 +1,27 @@
+<?php
+namespace yiiunit\framework\caching;
+use yii\caching\ApcCache;
+use yiiunit\TestCase;
+
+/**
+ * Class for testing APC cache backend
+ */
+class ApcCacheTest extends CacheTest
+{
+	private $_cacheInstance = null;
+
+	/**
+	 * @return ApcCache
+	 */
+	protected function getCacheInstance()
+	{
+		if(!extension_loaded("apc")) {
+			$this->markTestSkipped("APC not installed. Skipping.");
+		}
+
+		if($this->_cacheInstance === null) {
+			$this->_cacheInstance = new ApcCache();
+		}
+		return $this->_cacheInstance;
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/framework/caching/CacheTest.php b/tests/unit/framework/caching/CacheTest.php
new file mode 100644
index 0000000..ad2fcf5
--- /dev/null
+++ b/tests/unit/framework/caching/CacheTest.php
@@ -0,0 +1,82 @@
+<?php
+namespace yiiunit\framework\caching;
+use yiiunit\TestCase;
+use yii\caching\Cache;
+
+/**
+ * Base class for testing cache backends
+ */
+abstract class CacheTest extends TestCase
+{
+	/**
+	 * @return Cache
+	 */
+	abstract protected function getCacheInstance();
+
+	public function testSet()
+	{
+		$cache = $this->getCacheInstance();
+		$cache->set('string_test', 'string_test');
+		$cache->set('number_test', 42);
+		$cache->set('array_test', array('array_test' => 'array_test'));
+		$cache['arrayaccess_test'] = new \stdClass();
+	}
+
+	public function testGet()
+	{
+		$cache = $this->getCacheInstance();
+		$this->assertEquals('string_test', $cache->get('string_test'));
+
+		$this->assertEquals(42, $cache->get('number_test'));
+
+		$array = $cache->get('array_test');
+		$this->assertArrayHasKey('array_test', $array);
+		$this->assertEquals('array_test', $array['array_test']);
+
+		$this->assertInstanceOf('stdClass', $cache['arrayaccess_test']);
+	}
+
+	public function testMget()
+	{
+		$cache = $this->getCacheInstance();
+		$this->assertEquals(array('string_test' => 'string_test', 'number_test' => 42), $cache->mget(array('string_test', 'number_test')));
+	}
+
+	public function testExpire()
+	{
+		$cache = $this->getCacheInstance();
+		$cache->set('expire_test', 'expire_test', 2);
+		sleep(1);
+		$this->assertEquals('expire_test', $cache->get('expire_test'));
+		sleep(2);
+		$this->assertEquals(false, $cache->get('expire_test'));
+	}
+
+	public function testAdd()
+	{
+		$cache = $this->getCacheInstance();
+
+		// should not change existing keys
+		$cache->add('number_test', 13);
+		$this->assertEquals(42, $cache->get('number_test'));
+
+		// should store data is it's not there yet
+		$cache->add('add_test', 13);
+		$this->assertEquals(13, $cache->get('add_test'));
+	}
+
+	public function testDelete()
+	{
+		$cache = $this->getCacheInstance();
+
+		$cache->delete('number_test');
+		$this->assertEquals(null, $cache->get('number_test'));
+	}
+
+	public function testFlush()
+	{
+		$cache = $this->getCacheInstance();
+		$cache->flush();
+		$this->assertEquals(null, $cache->get('add_test'));
+	}
+}
diff --git a/tests/unit/framework/caching/DbCacheTest.php b/tests/unit/framework/caching/DbCacheTest.php
new file mode 100644
index 0000000..3977ee8
--- /dev/null
+++ b/tests/unit/framework/caching/DbCacheTest.php
@@ -0,0 +1,70 @@
+<?php
+namespace yiiunit\framework\caching;
+use yii\caching\DbCache;
+use yiiunit\TestCase;
+
+/**
+ * Class for testing file cache backend
+ */
+class DbCacheTest extends CacheTest
+{
+	private $_cacheInstance;
+	private $_connection;
+
+	function __construct()
+	{
+		if (!extension_loaded('pdo') || !extension_loaded('pdo_mysql')) {
+			$this->markTestSkipped('pdo and pdo_mysql extensions are required.');
+		}
+
+		$this->getConnection()->createCommand("
+			CREATE TABLE IF NOT EXISTS tbl_cache (
+				id char(128) NOT NULL,
+				expire int(11) DEFAULT NULL,
+				data LONGBLOB,
+				PRIMARY KEY (id),
+				KEY expire (expire)
+			);
+		")->execute();
+	}
+
+	/**
+	 * @param bool $reset whether to clean up the test database
+	 * @return \yii\db\Connection
+	 */
+	function getConnection($reset = true)
+	{
+		if($this->_connection === null) {
+			$params = $this->getParam('mysql');
+			$db = new \yii\db\Connection;
+			$db->dsn = $params['dsn'];
+			$db->username = $params['username'];
+			$db->password = $params['password'];
+			if ($reset) {
+				$db->open();
+				$lines = explode(';', file_get_contents($params['fixture']));
+				foreach ($lines as $line) {
+					if (trim($line) !== '') {
+						$db->pdo->exec($line);
+					}
+				}
+			}
+			$this->_connection = $db;
+		}
+		return $this->_connection;
+	}
+
+
+	/**
+	 * @return DbCache
+	 */
+	protected function getCacheInstance()
+	{
+		if($this->_cacheInstance === null) {
+			$this->_cacheInstance = new DbCache(array(
+				'db' => $this->getConnection(),
+			));
+		}
+		return $this->_cacheInstance;
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/framework/caching/FileCacheTest.php b/tests/unit/framework/caching/FileCacheTest.php
new file mode 100644
index 0000000..1f6debd
--- /dev/null
+++ b/tests/unit/framework/caching/FileCacheTest.php
@@ -0,0 +1,25 @@
+<?php
+namespace yiiunit\framework\caching;
+use yii\caching\FileCache;
+use yiiunit\TestCase;
+
+/**
+ * Class for testing file cache backend
+ */
+class FileCacheTest extends CacheTest
+{
+	private $_cacheInstance = null;
+
+	/**
+	 * @return FileCache
+	 */
+	protected function getCacheInstance()
+	{
+		if($this->_cacheInstance === null) {
+			$this->_cacheInstance = new FileCache(array(
+				'cachePath' => '@yiiunit/runtime/cache',
+			));
+		}
+		return $this->_cacheInstance;
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/framework/caching/MemCacheTest.php b/tests/unit/framework/caching/MemCacheTest.php
new file mode 100644
index 0000000..e4804d9
--- /dev/null
+++ b/tests/unit/framework/caching/MemCacheTest.php
@@ -0,0 +1,27 @@
+<?php
+namespace yiiunit\framework\caching;
+use yii\caching\MemCache;
+use yiiunit\TestCase;
+
+/**
+ * Class for testing memcache cache backend
+ */
+class MemCacheTest extends CacheTest
+{
+	private $_cacheInstance = null;
+
+	/**
+	 * @return MemCache
+	 */
+	protected function getCacheInstance()
+	{
+		if(!extension_loaded("memcache")) {
+			$this->markTestSkipped("memcache not installed. Skipping.");
+		}
+
+		if($this->_cacheInstance === null) {
+			$this->_cacheInstance = new MemCache();
+		}
+		return $this->_cacheInstance;
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/framework/caching/MemCachedTest.php b/tests/unit/framework/caching/MemCachedTest.php
new file mode 100644
index 0000000..59396df
--- /dev/null
+++ b/tests/unit/framework/caching/MemCachedTest.php
@@ -0,0 +1,29 @@
+<?php
+namespace yiiunit\framework\caching;
+use yii\caching\MemCache;
+use yiiunit\TestCase;
+
+/**
+ * Class for testing memcache cache backend
+ */
+class MemCachedTest extends CacheTest
+{
+	private $_cacheInstance = null;
+
+	/**
+	 * @return MemCache
+	 */
+	protected function getCacheInstance()
+	{
+		if(!extension_loaded("memcached")) {
+			$this->markTestSkipped("memcached not installed. Skipping.");
+		}
+
+		if($this->_cacheInstance === null) {
+			$this->_cacheInstance = new MemCache(array(
+				'useMemcached' => true,
+			));
+		}
+		return $this->_cacheInstance;
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/framework/caching/WinCacheTest.php b/tests/unit/framework/caching/WinCacheTest.php
new file mode 100644
index 0000000..b78d57b
--- /dev/null
+++ b/tests/unit/framework/caching/WinCacheTest.php
@@ -0,0 +1,31 @@
+<?php
+namespace yiiunit\framework\caching;
+use yii\caching\FileCache;
+use yiiunit\TestCase;
+
+/**
+ * Class for testing wincache backend
+ */
+class WinCacheTest extends CacheTest
+{
+	private $_cacheInstance = null;
+
+	/**
+	 * @return WinCache
+	 */
+	protected function getCacheInstance()
+	{
+		if(!extension_loaded('wincache')) {
+			$this->markTestSkipped("Wincache not installed. Skipping.");
+		}
+
+		if(!ini_get('wincache.ucenabled')) {
+			$this->markTestSkipped("Wincache user cache disabled. Skipping.");
+		}
+
+		if($this->_cacheInstance === null) {
+			$this->_cacheInstance = new WinCache();
+		}
+		return $this->_cacheInstance;
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/framework/caching/XCacheTest.php b/tests/unit/framework/caching/XCacheTest.php
new file mode 100644
index 0000000..e1ed844
--- /dev/null
+++ b/tests/unit/framework/caching/XCacheTest.php
@@ -0,0 +1,27 @@
+<?php
+namespace yiiunit\framework\caching;
+use yii\caching\XCache;
+use yiiunit\TestCase;
+
+/**
+ * Class for testing xcache backend
+ */
+class XCacheTest extends CacheTest
+{
+	private $_cacheInstance = null;
+
+	/**
+	 * @return XCache
+	 */
+	protected function getCacheInstance()
+	{
+		if(!function_exists("xcache_isset")) {
+			$this->markTestSkipped("XCache not installed. Skipping.");
+		}
+
+		if($this->_cacheInstance === null) {
+			$this->_cacheInstance = new XCache();
+		}
+		return $this->_cacheInstance;
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/framework/caching/ZendDataCacheTest.php b/tests/unit/framework/caching/ZendDataCacheTest.php
new file mode 100644
index 0000000..91dfbb5
--- /dev/null
+++ b/tests/unit/framework/caching/ZendDataCacheTest.php
@@ -0,0 +1,27 @@
+<?php
+namespace yiiunit\framework\caching;
+use yii\caching\ZendDataCache;
+use yiiunit\TestCase;
+
+/**
+ * Class for testing Zend cache backend
+ */
+class ZendDataCacheTest extends CacheTest
+{
+	private $_cacheInstance = null;
+
+	/**
+	 * @return ZendDataCache
+	 */
+	protected function getCacheInstance()
+	{
+		if(!function_exists("zend_shm_cache_store")) {
+			$this->markTestSkipped("Zend Data cache not installed. Skipping.");
+		}
+
+		if($this->_cacheInstance === null) {
+			$this->_cacheInstance = new ZendDataCache();
+		}
+		return $this->_cacheInstance;
+	}
+}
\ No newline at end of file