public function testAddTimestampsForDifferentEntities()
 {
     $article = new Article($this->getConn());
     $article->title = 'Foo';
     $article->save();
     $writer = new Writer($this->getConn());
     $writer->save();
     $datetime = new \DateTime();
     $this->assertEquals($datetime, $article->created_at);
     $this->assertEquals($datetime, $article->updated_at);
     $this->assertEquals($datetime, $writer->createdAt);
     $this->assertEquals($datetime, $writer->anotherCreate);
     $this->assertEquals($datetime, $writer->updatedAt);
     $this->assertEquals($datetime, $writer->anotherUpdate);
     //check that other fields haven't been set on different entities
     $this->assertNull($writer->created_at);
     $this->assertNull($writer->updated_at);
     $this->assertNull($article->createdAt);
     $this->assertNull($article->anotherCreate);
     $this->assertNull($article->updatedAt);
     $this->assertNull($article->anotherUpdate);
 }