example.m

[KWMatchers defineMatcher:@"beUppercaseString" as:^(KWMatcherBuilder *builder) {
  [builder match:^(id subject) {
    if ([subject isKindOfClass:[NSString class]]) {
      NSString *string = (NSString *)subject;
      return [[string uppercaseString] isEqualToString:string];
    } else {
      return NO;
    }
  }];
}];

 [[@"SOME_STRING" should] beUppercaseString]