refs #4233 check if it creates the correct instance

tests/PHPUnit/Core/TravisEnvironmentTest.php

@@ -13,8 +13,22 @@ class TravisEnvironmentTest extends PHPUnit_Framework_TestCase
     {
         $mysqlAdapter = getenv('MYSQL_ADAPTER');
 
-        if (!empty($mysqlAdapter)) {
-            $this->assertTrue(in_array($mysqlAdapter, array('PDO_MYSQL', 'MYSQLI')));
+        if (empty($mysqlAdapter)) {
+            return;
         }
+
+        $this->assertTrue(in_array($mysqlAdapter, array('PDO_MYSQL', 'MYSQLI')));
+
+        $db = Piwik\Db::get();
+
+        switch ($mysqlAdapter) {
+            case 'PDO_MYSQL':
+                $this->assertInstanceOf('\Piwik\Db\Adapter\Pdo\Mysql', $db);
+                break;
+            case 'MYSQLI':
+                $this->assertInstanceOf('\Piwik\Db\Adapter\Mysqli', $db);
+                break;
+        }
+
     }
 }
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