Validates that a DateTime is before or the same moment as date.
When using this matcher with methods like expectResponse, hasResponse, hasHeaders, hasBody,
the compared value will be parsed into a DateTime prior to running this matcher.
Source
Matcher isBeforeOrSameMomentAs(DateTime date) {
return predicate((DateTime d) => d.isBefore(date) || d == date,
"before or same moment as ${date.toIso8601String()}");
}