Fix for issue #253 clone datetime (#613)

* Clone datetime before changing timezone

* Test for clone datetime before changing timezone

src/Core/Query/Helper.php

@@ -110,7 +110,7 @@ class Helper
         switch (true) {
             // input of datetime object
             case $input instanceof \DateTimeInterface:
-                // no work needed
+                $input = clone $input;
                 break;
             // input of timestamp or date/time string
             case is_string($input) || is_numeric($input):

tests/QueryType/Update/RequestBuilderTest.php

@@ -264,6 +264,21 @@ class RequestBuilderTest extends TestCase
         );
     }
 
+    public function testBuildAddXmlWithDateTimeImmutable()
+    {
+        $timezone = new \DateTimeZone('Europe/London');
+        $date = new \DateTime('2013-01-15 14:41:58', $timezone);
+
+        $command = new AddCommand();
+        $command->addDocument(
+            new Document(['id' => 1, 'datetime' => $date])
+        );
+
+        $this->builder->buildAddXml($command, $this->query);
+
+        $this->assertEquals($timezone->getName(), $date->getTimezone()->getName());
+    }
+
     public function testBuildAddXmlWithFieldModifierAndNullValue()
     {
         $doc = new Document();