public function testIncrementItemsReturnsFalseIfNonWritable()
 {
     $this->_storage->setItem('key', 10);
     $this->_options->setWritable(false);
     $this->assertFalse($this->_storage->incrementItems(array('key' => 5)));
     $this->assertEquals(10, $this->_storage->getItem('key'));
 }