[tests] Use @requires annotation when possible

Author: nicolas-grekas

Test/DoctrineTestHelper.php

@@ -29,8 +29,8 @@ class DoctrineTestHelper
      */
     public static function createTestEntityManager()
     {
-        if (!class_exists('PDO') || !in_array('sqlite', \PDO::getAvailableDrivers())) {
-            \PHPUnit_Framework_TestCase::markTestSkipped('This test requires SQLite support in your environment');
+        if (!extension_loaded('pdo_sqlite')) {
+            \PHPUnit_Framework_TestCase::markTestSkipped('Extension pdo_sqlite is required.');
         }
 
         $config = new \Doctrine\ORM\Configuration();

Tests/Logger/DbalLoggerTest.php

@@ -132,12 +132,11 @@ public function testLogLongString()
         ));
     }
 
+    /**
+     * @requires extension mbstring
+     */
     public function testLogUTF8LongString()
     {
-        if (!function_exists('mb_detect_encoding')) {
-            $this->markTestSkipped('Testing log shortening of utf8 charsets requires the mb_detect_encoding() function.');
-        }
-
         $logger = $this->getMock('Symfony\\Component\\HttpKernel\\Log\\LoggerInterface');
 
         $dbalLogger = $this