dispatch_sync on main queue hangs in unit test
问题 I was having some trouble unit testing some grand central dispatch code with the built in Xcode unit testing framework, SenTestingKit. I managed to boil my problem done to this. I have a unit test that builds a block and tries to execute it on the main thread. However, the block is never actually executed, so the test hangs because it's a synchronous dispatch. - (void)testSample { dispatch_sync(dispatch_get_main_queue(), ^(void) { NSLog(@"on main thread!"); }); STFail(@"FAIL!"); } What is it