public function testAddMonth()
{
$date = new DateTime2('2014-01-01');
$date->addMonth();
$this->assertEquals(1, $date->getDay());
$this->assertEquals(2, $date->getMonth());
$returned = $date->addMonth(-2);
$this->assertEquals(1, $date->getDay());
$this->assertEquals(12, $date->getMonth());
$this->assertTrue($returned === $date);
}
