How to test a sendAsynchronousRequest: on XCTest

Question

Sorry for the noob question, but I'm trying to test a connection, but I'm not able do verify the return of the request, because the test ends before the completion handler have a chance to execute. To ilustrate:

-(void)testConnection
{

    [[Conector sharedInstance] performAsynchronousRequestWithServerRequest:_srvRequest completionHandler:^(RequestAsynchronousStatus finishStatus, NSData *data) {
        if (finishStatus == RequestAsynchronousOK){
            _data = data;
            NSLog(@"Data OK");
        }
    }];

    XCTAssertNotNil(_data, @"Data was nil");

}

When I try to assert, _data will always be nil, because the completion handler wasn't executed yet. There is a mechanism to force the test to wait until I have some response from the sendAsynchronousRequest: method. Thanks in advance.

Answer 1

This is now included in XCode 6:

Obj-C example here:

XCTest and asynchronous testing in Xcode 6

Answer 2

Here's another alternative, XCAsyncTestCase based upon the GHUnit version:

https://github.com/iheartradio/xctest-additions

Usage is the same, just import and subclass XCAsyncTestCase.

@implementation TestAsync
- (void)testBlockSample
{
    [self prepare];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(){
        sleep(1.0);
        [self notify:kXCTUnitWaitStatusSuccess];
    });
    // Will wait for 2 seconds before expecting the test to have status success
    // Potential statuses are:
    //    kXCTUnitWaitStatusUnknown,    initial status
    //    kXCTUnitWaitStatusSuccess,    indicates a successful callback
    //    kXCTUnitWaitStatusFailure,    indicates a failed callback, e.g login operation failed
    //    kXCTUnitWaitStatusCancelled,  indicates the operation was cancelled
    [self waitForStatus:kXCTUnitWaitStatusSuccess timeout:2.0];
}

Answer 3

This looks like exactly what you need:

XCAsyncTestCase: Asynchronous capable SenTestCase subclass.

Basically, you should write your test like this:

- (void)testConnection
{
    [[Conector sharedInstance] performAsynchronousRequestWithServerRequest:_srvRequest completionHandler:^(RequestAsynchronousStatus finishStatus, NSData *data) {
        if (finishStatus == RequestAsynchronousOK)
        {
            _data = data;
            [self notify:XCTAsyncTestCaseStatusSucceeded];
            NSLog(@"Data OK");
        }
    }];

    [self waitForTimeout:10];

    XCTAssertNotNil(_data, @"Data was nil");
}

Notice the waitForTimeout: call and the notify: calls. 10 seconds should be enough for the test, though it would depend on the request itself.

You could even get more specific and wait for a certain status, like so:

[self waitForStatus: XCTAsyncTestCaseStatusSucceeded timeout:10];

This way, if the connection fails to notify the XCTAsyncTestCaseStatusSucceeded status, the wait call will timeout and your test would fail (as it should).