isAfter function Null safety

Matcher isAfter(
  1. DateTime date

Validates that a DateTime is after date.

This matcher has additional behavior when used in expectResponse, hasResponse, hasHeaders, hasBody: if the actual value is a String, it will attempted to be parsed into a DateTime first. If parsing fails, this matcher will fail.

    expectResponse(response, 200, headers: {"x-timestamp": isAfter(DateTime())});


Matcher isAfter(DateTime date) {
  return predicate(
      (DateTime d) => d.isAfter(date), "after ${date.toIso8601String()}");