Testing the same code with different input data
I've got one possible solution from Max Lunin:

NSArray *successCodes = @[@200, @201, @202, @203, @204, @205, @206];
for (NSNumber *statusCode in successCodes) {
    it([NSString stringWithFormat:@"should call operationSucceeded for status code %@", statusCode], ^{
        MKNetworkOperation *op =[[MKNetworkOperation alloc] initWithURLString:@"http://example.com/api" params:nil httpMethod:@"GET"];
        [op stub:@selector(notifyCache)];
        NSHTTPURLResponse *response = [[NSHTTPURLResponse alloc] initWithURL:nil
                                                                  statusCode:[statusCode intValue]
                                                                 HTTPVersion:nil
                                                                headerFields:nil];
        [op stub:@selector(response) andReturn:response];
        [[op should] receive:@selector(operationSucceeded)];
        [op connectionDidFinishLoading:[NSURLConnection nullMock]];
    });
}


It solves the problem with error explanation. It will tell something like: 'Operation, should call operationSucceeded for status code 202' [FAILED], expected subject to receive -operationSucceeded exactly 1 time, but received it 0 times

Any other more clear solutions?