Enhancement: implement ping() for all drivers

 * h/t @stof and @deeky666
 * add two test cases for the general connection test
 * remove the ConnectionException method I added originally

lib/Doctrine/DBAL/Connection.php

@@ -1497,10 +1497,22 @@ class Connection implements DriverConnection
      */
     public function ping()
     {
-        if ( ! ($this->_conn instanceof PingableConnection)) {
-            throw ConnectionException::unsupportedFeature('ping');
+        if ( ! $this->_isConnected) {
+            return false; // Don't connect if not done yet. It will be lazy on first use
         }
 
-        return $this->_conn->ping();
+        if ($this->_conn instanceof PingableConnection) {
+            return $this->_conn->ping();
+        }
+
+        try {
+            $this->query($this->_platform->getDummySelectSQL());
+            return true;
+        } catch (DBALException $e) {
+            // As the underlying connection is unset, the next query will connect again thanks to the lazyness
+            $this->close();
+        }
+
+        return false;
     }
 }

lib/Doctrine/DBAL/ConnectionException.php

@@ -57,12 +57,4 @@ class ConnectionException extends DBALException
     {
         return new self("May not alter the nested transaction with savepoints behavior while a transaction is open.");
     }
-
-    /**
-     * @return \Doctrine\DBAL\ConnectionException
-     */
-    public static function unsupportedFeature($feature)
-    {
-        return new self(sprintf("The '%' feature is not supported by this connection/driver.", $feature));
-    }
 }

tests/Doctrine/Tests/DBAL/Functional/ConnectionTest.php

@@ -216,4 +216,15 @@ class ConnectionTest extends \Doctrine\Tests\DbalFunctionalTestCase
     {
         $this->assertEquals($this->_conn->quote("foo", Type::STRING), $this->_conn->quote("foo", \PDO::PARAM_STR));
     }
+
+    public function testPingDoesNotTriggerConnect()
+    {
+        $this->assertFalse($this->_conn->ping());
+    }
+
+    public function testPingReturnsTrueWhenConnectionIsPingedOrOpen()
+    {
+        $this->_conn->executeQuery($this->_conn->getDatabasePlatform()->getDummySelectSQL());
+        $this->assertTrue($this->_conn->ping());
+    }
 }