public function testMonths()
 {
     $ci = new CarbonInterval(0, 1);
     $this->assertInstanceOfCarbonInterval($ci);
     $this->assertCarbonInterval($ci, 0, 1, 0, 0, 0, 0);
     $ci = CarbonInterval::months(2);
     $this->assertInstanceOfCarbonInterval($ci);
     $this->assertCarbonInterval($ci, 0, 2, 0, 0, 0, 0);
     $ci = CarbonInterval::month();
     $this->assertInstanceOfCarbonInterval($ci);
     $this->assertCarbonInterval($ci, 0, 1, 0, 0, 0, 0);
     $ci = CarbonInterval::month(3);
     $this->assertInstanceOfCarbonInterval($ci);
     $this->assertCarbonInterval($ci, 0, 3, 0, 0, 0, 0);
 }
 public function testDiffFilteredNegativeWithSignWithSecondObject()
 {
     $dt1 = Carbon::createFromDate(2001, 1, 31);
     $dt2 = Carbon::createFromDate(1999, 1, 1);
     $this->assertSame(-12, $dt1->diffFiltered(CarbonInterval::month(), function (Carbon $date) {
         return $date->year === 2000;
     }, $dt2, false));
 }