void expect(actual, matcher, { String reason, bool verbose: false, formatter })

Assert that actual matches matcher.

See test_package.expect for details. This is a variant of that function that additionally verifies that there are no asynchronous APIs that have not yet resolved.

Source 

void expect(dynamic actual, dynamic matcher, {
  String reason,
  bool verbose: false,
  dynamic formatter
}) {
  TestAsyncUtils.guardSync();
  test_package.expect(actual, matcher, reason: reason, verbose: verbose, formatter: formatter);
}