refund(10, Carbon::parse('2021-01-01'), Carbon::parse('2021-01-31'), RecurringInvoice::FREQUENCY_MONTHLY); $this->assertEquals(9.68, $refund); $this->assertEquals(30, Carbon::parse('2021-01-01')->diffInDays(Carbon::parse('2021-01-31'))); } public function testProRataRefundYearly() { $pro_rata = new ProRata(); $refund = $pro_rata->refund(10, Carbon::parse('2021-01-01'), Carbon::parse('2021-01-31'), RecurringInvoice::FREQUENCY_ANNUALLY); $this->assertEquals(0.82, $refund); } public function testDiffInDays() { $this->assertEquals(30, Carbon::parse('2021-01-01')->diffInDays(Carbon::parse('2021-01-31'))); } }