How can you test the contents of a UIAlertAction handler with OCMock

Question

I\'ve got an app where I push a UIAlertController with several custom UIAlertActions. Each UIAlertAction performs unique tasks in the

Answer 1

After some playing around I finally figure it out. Turns out that the handler block can be cast as a function pointer and the function pointer can be executed.

Like so

UIAlertAction *action = myAlertController.actions[0];
void (^someBlock)(id obj) = [action valueForKey:@"handler"];
someBlock(action);

Here's an example of how it would be used.

-(void)test_verifyThatIfUserSelectsTheFirstActionOfMyAlertControllerSomeMethodIsCalled {

    //Setup expectations
    [[_partialMockViewController expect] someMethod];

    //When the UIAlertController is presented automatically simulate a "tap" of the first button
    [[_partialMockViewController stub] presentViewController:[OCMArg checkWithBlock:^BOOL(id obj) {

        XCTAssert([obj isKindOfClass:[UIAlertController class]]);

        UIAlertController *alert = (UIAlertController*)obj;

        //Get the first button
        UIAlertAction *action = alert.actions[0];

        //Cast the pointer of the handle block into a form that we can execute
        void (^someBlock)(id obj) = [action valueForKey:@"handler"];

        //Execute the code of the join button
        someBlock(action);
    }]
                                         animated:YES
                                       completion:nil];

   //Execute the method that displays the UIAlertController
   [_viewControllerUnderTest methodThatDisplaysAlertController];

   //Verify that |someMethod| was executed
   [_partialMockViewController verify];
}

Answer 2

With a bit of clever casting, I've found a way to do this in Swift (2.2):

extension UIAlertController {

    typealias AlertHandler = @convention(block) (UIAlertAction) -> Void

    func tapButtonAtIndex(index: Int) {
        let block = actions[index].valueForKey("handler")
        let handler = unsafeBitCast(block, AlertHandler.self)

        handler(actions[index])
    }

}

This allows you to call alert.tapButtonAtIndex(1) in your test and have the correct handler executed.

(I would only use this in my test target, btw)