anchor.diff:  final _isATypeError = const isInstanceOf<TypeError>();
   
   void main() {
  +  test('valid values covers all keys', () {
  +    expect(_validValues.keys, orderedEquals(_expectedOrder));
  +  });
  +
  +  test('inlavid values covers all keys', () {
  +    expect(_invalidValues.keys, orderedEquals(_expectedOrder));
  +  });
  +
     group('nullable', () {
       group('unwrapped', () {
         _nullableTests(nullable.testFactory, nullable.testFromJson);
  
positive.code:     }
    });
  }
  
  final _excludeIfNullKeys = [
    'dateTime',
  
negative.code:     expect(json.keys, orderedEquals(_expectedOrder));
    });
  
    test('valid values round-trip', () {
      expect(loudEncode(_validValues), loudEncode(fromJson(_validValues)));
    });
  
    group('a bad value for', () {
      for (var e in _invalidValues.entries) {
        test('`${e.key}` fails', () {
          var copy = new Map<String, dynamic>.from(_validValues);
          copy[e.key] = e.value;
          expect(() => fromJson(copy),
              throwsA(anyOf(_isATypeError, _isACastError, isArgumentError)));
  