hasDate function
Matches the date from a HasDate.
Implementation
Matcher hasDate(Object? year, [Object? month = 1, Object? day = 1]) =>
isA<HasDate>()
.having((d) => d.year, 'year', year)
.having((d) => d.month, 'month', month)
.having((d) => d.day, 'day', day);