Test case example to test response of an asynchronous networking request with XCTestExpectation APIs

TestURLConnection.m

- (void)testAsynchronousURLConnection {
    
    // Create request
    NSURL *URL = [NSURL URLWithString:@"http://httpbin.org/get"];
    
    NSString *description = [NSString stringWithFormat:@"GET %@", URL];
    
    XCTestExpectation *expectation = [self expectationWithDescription:description];
    
    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *task = [session dataTaskWithURL:URL
                                        completionHandler:^(NSData *data,
                                                            NSURLResponse *response,
                                                            NSError * error)
    {
    
        XCTAssertNotNil(data, @"data should not be nil");
        XCTAssertNil(error, @"error shuold be nill");
        
        if ([response isKindOfClass:[NSHTTPURLResponse class]]) {
            NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
            XCTAssertEqual(httpResponse.statusCode, 200, @"HTTP response status code should be return 200");
            XCTAssertEqualObjects(httpResponse.URL.absoluteString, URL.absoluteString, @"HTTP response URL should be equal to Original URL");
            XCTAssertEqualObjects(httpResponse.MIMEType, @"application/json", @"HTTP response content type should be application/json");
        } else {
            XCTFail(@"Response was not NSHTTPURLResponse");
        }
        [expectation fulfill];
    }];
    
    // fire request
    [task resume];
    
    // wait timeout
    [self waitForExpectationsWithTimeout:task.originalRequest.timeoutInterval handler:^(NSError * _Nullable error) {
        if (error != nil) {
            NSLog(@"ERROR: %@", error.localizedDescription);
        }
        [task cancel];
    }];
}

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