Example asynchronous GHUnit test.

AsyncTest.h

#import <SenTestingKit/SenTestingKit.h>

@interface AsyncTests : SenTestCase {
	NSCondition* condition;
	BOOL operationSucceeded;
}

@end

AsyncTests.m

#import "AsyncTests.h"

@implementation AsyncTests

- (void) setUp
{
	condition = [[NSCondition alloc] init];
	operationSucceeded = NO;
}

- (void) tearDown
{
	[condition release];
}

- (void) testAsynchronousMethodCall
{
	// Create and start an asynchronous operation
	NSOperationQueue* queue = [[[NSOperationQueue alloc] init] autorelease];
	MyOperation* operation = [[[MyOperation alloc] init] autorelease];
	[queue addOperation:operation];
	
	// Block and wait for one of the delegate methods to be called
	[condition lock];
	[condition wait];
	[condition unlock];
	
	// Our operation has completed at this point, so we can check if it was successful
	STAssertTrue(operationSucceeded, @"");
}

- (void) myOperationDidFinish
{
	operationSucceeded = YES;
	
	[condition lock];
	[condition signal];
	[condition unlock];
}

- (void) myOperationDidFailWithError:(NSError*)error
{
	operationSucceeded = NO;
	
	[condition lock];
	[condition signal];
	[condition unlock];
}

@end

What happens if operation fails so badly that neither delegate method is called?

Good point. I guess you could set a timer to go off after some delay, and in its target method you could check if the asynchronous operation is still in progress. If so, you can kill it and signal the condition without setting the operationSucceeded flag, making the test fail.

To solve the problem where neither delegate method is called, you could replace -wait with -waitUntilDate:

NSDate *date = [[NSDate date] dateByAddingTimeInterval:10];
[condition lock];
BOOL timedOut = ![self.condition waitUntilDate:date];
[self.condition unlock];

if (timedOut) {
  // do something
} else {
    GHAssertTrue(self.operationSucceeded, nil);
}

I encountered this problem when testing async code on the command line. Specifically, I was testing the outcome of an ASIHTTRequest. On the command line, my asynchronous tests were hanging so I implemented the 10 sec timeout with -waitUntilDate:. Unfortunately, I have not discovered the root of the problem: why are the async tests hanging on the command line?

OCUnit / SenTesting framework does not run within the normal RunLoop; which NSURLConnection relies on to execute. This is why the request never starts and none of the delegate methods are ever called. I tried to make this work in OCUnit for some time (including manually 'spinning' the RunLoop) with no success. The simplest/best alternative is using another test framework which does run tests in full application mode. I recommend GHUnit for ease of use; it's quick to set up and there are plenty of examples online.