import assert from 'assert' ; import differenceInCalendarISOWeekYears from '.' ; describe ( 'differenceInCalendarISOWeekYears' , ( ) => { it ( 'returns the number of calendar ISO week-numbering years between the given dates' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( 2012 , 6 , 2 , 18 , 0 ) , new Date ( 2011 , 6 , 2 , 6 , 0 ) ) ; assert ( result === 1 ) ; } ) ; it ( 'returns a negative number if the time value of the first date is smaller' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( 2011 , 6 , 2 , 6 , 0 ) , new Date ( 2012 , 6 , 2 , 18 , 0 ) ) ; assert ( result === - 1 ) ; } ) ; it ( 'accepts timestamps' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( 2014 , 6 , 2 ) . getTime ( ) , new Date ( 2010 , 6 , 2 ) . getTime ( ) ) ; assert ( result === 4 ) ; } ) ; it ( 'handles dates before 100 AD' , ( ) => { const firstDate = new Date ( 0 ) ; firstDate . setFullYear ( 14 , 0 , 1 ) ; firstDate . setHours ( 0 , 0 , 0 , 0 ) ; const secondDate = new Date ( 0 ) ; secondDate . setFullYear ( 0 , 0 , 1 ) ; secondDate . setHours ( 0 , 0 , 0 , 0 ) ; const result = differenceInCalendarISOWeekYears ( firstDate , secondDate ) ; assert ( result === 15 ) ; } ) ; describe ( 'edge cases' , ( ) => { it ( 'the difference is less than an ISO year, but the given dates are in different calendar ISO years' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( 2012 , 0 , 2 ) , new Date ( 2012 , 0 , 1 ) ) ; assert ( result === 1 ) ; } ) ; it ( 'the same for the swapped dates' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( 2012 , 0 , 1 ) , new Date ( 2012 , 0 , 2 ) ) ; assert ( result === - 1 ) ; } ) ; it ( 'the ISO weeks and weekdays of the given dates are the same' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( 2013 , 11 , 30 ) , new Date ( 2012 , 0 , 2 ) ) ; assert ( result === 2 ) ; } ) ; it ( 'the given dates are the same' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( 2014 , 8 , 5 , 0 , 0 ) , new Date ( 2014 , 8 , 5 , 0 , 0 ) ) ; assert ( result === 0 ) ; } ) ; it ( 'does not return -0 when the given dates are the same' , ( ) => { function isNegativeZero ( x ) { return x === 0 && 1 / x < 0 ; } const result = differenceInCalendarISOWeekYears ( new Date ( 2014 , 8 , 5 , 0 , 0 ) , new Date ( 2014 , 8 , 5 , 0 , 0 ) ) ; const resultIsNegative = isNegativeZero ( result ) ; assert ( resultIsNegative === false ) ; } ) ; } ) ; it ( 'returns NaN if the first date is `Invalid Date`' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( NaN ) , new Date ( 2017 , 0 , 1 ) ) ; assert ( isNaN ( result ) ) ; } ) ; it ( 'returns NaN if the second date is `Invalid Date`' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( 2017 , 0 , 1 ) , new Date ( NaN ) ) ; assert ( isNaN ( result ) ) ; } ) ; it ( 'returns NaN if the both dates are `Invalid Date`' , ( ) => { const result = differenceInCalendarISOWeekYears ( new Date ( NaN ) , new Date ( NaN ) ) ; assert ( isNaN ( result ) ) ; } ) ; it ( 'throws TypeError exception if passed less than 2 arguments' , ( ) => { assert . throws ( differenceInCalendarISOWeekYears . bind ( null ) , TypeError ) ; assert . throws ( differenceInCalendarISOWeekYears . bind ( null , 1 ) , TypeError ) ; } ) ; } ) ;